I have some code I wrote in the book of shaders editor:
#ifdef GL_ES
precision mediump float;
#endif
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;
float remap(float a, float b, float c, float d, float t) {
return ((t - a) / (b - a)) * (d-c) + c;
}
float outline(vec2 st) {
return smoothstep(0.99, 1.0, st.y) + smoothstep(0.99, 1.0, st.x) + smoothstep(0.01, 0.0, st.y) + smoothstep(0.01, 0.0, st.x);
}
float mouseFoo(vec2 scaledSt, vec2 u_mouse, float scaleVal) {
vec2 scaledMouse = u_mouse * scaleVal;
if(scaledSt.x < ceil(scaledMouse.x) && scaledSt.x > floor(scaledMouse.x) && scaledSt.y < ceil(scaledMouse.y) && scaledSt.y > floor(scaledMouse.y)) {
// if(u_mouse.x < 100.0) {
return 1.0;
} else {
return 0.0;
}
}
void main(){
vec2 st = gl_FragCoord.xy/u_resolution.xy;
vec3 color = vec3(0.03,0.07,0.15);
vec3 redColor = vec3(1.0, 0.0, 0.0);
vec3 outlineColor = vec3(1.0);
float floorSt;
float scaleVal = 5.0;
vec2 scaledSt = st * scaleVal;
// tile
st *= scaleVal;
floorSt = floor(st.x);
st = fract(st);
// inner color
color = mix(color, redColor, mouseFoo(scaledSt, u_mouse/u_resolution.xy, scaleVal));
// outline
color = mix(color, outlineColor, outline(st));
gl_FragColor = vec4(color, 1.0 );
}
I'm wondering if it's possible to have the red color tween to the blue color when a box is hovered off? I think I might have an idea of how to do it if I were to write data to a texture and look that up, but even then I'm not entirely sure.
Use mix
Use mix to interpolate between red and blue. You need another variable that transitions from 0-1 to do the blend, which is mix's 3rd parameter.
ShaderToy example:
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
// Normalized pixel coordinates (from 0 to 1)
vec2 uv = fragCoord/iResolution.xy;
vec3 red = vec3(1,0,0);
vec3 blue = vec3(0,0,1);
// Output to screen
fragColor = vec4(mix(red, blue, uv.x),1.0);
}
which produces:
In your case, you'll want the 3rd parameter (the alpha or lerp parameter) to be driven over some time (say, .2 seconds) after the mouse entered the hover area. You'll need to do one of the following:
Detect the hover entered at a higher level and then pass the mouse down time in as a uniform
Drive the 3rd parameter directly from a uniform
I write a little program to explain simply my problem, I try to change the pixel position of picture with a texture one where the component x is the direction, and where the other represent the velocity. The final objective is to use my data from CPU where are compute a NAVIER-STROKE fluid to move the pixel in GLSL. The CPU code is in Processing java library.
I try to undestand what is buggy in my code, but I don't understand how work the pixel translation.
in the first I transform my direction in value color from 0 to 255 in the CPU and after in the GPU transform this one in vectorial direction, and multiply this one by the velocity and scale this one in 1x1 but that's don't work... sorry if my explication is not really understable, but english is not really fluent.
link to the sketch
Processing :
PImage tex_velocity, tex_direction ;
PShader warping;
PImage img ;
int grid_w, grid_h ;
void setup() {
size(600,375,P2D);
// img = loadImage("pirate_small.jpg");
img = loadImage("puros_girl_small.jpg");
grid_w = 60 ;
grid_h = 37 ;
tex_velocity = createImage(grid_w,grid_h,RGB);
tex_direction = createImage(grid_w,grid_h,RGB);
warping = loadShader("shader/warp/rope_warp_frag.glsl");
noise_img(tex_velocity, 20, .1, .1); // max translate for the pixel
noise_img(tex_direction, 360, .1, .1); // degree direction
}
void draw() {
println(frameRate);
if(frameCount%30 == 0) {
noise_img(tex_velocity, 20, .1, .1); // max translate for the pixel
noise_img(tex_direction, 360, .1, .1); // degree direction
}
warping.set("mode", 0) ;
warping.set("texture",img);
warping.set("roof_component_colour",g.colorModeX);
warping.set("wh_ratio",1f/grid_w, 1f/grid_h);
warping.set("vel_texture",tex_velocity);
warping.set("dir_texture",tex_direction);
shader(warping);
image(img,0,0);
resetShader();
image(tex_velocity,5,5);
image(tex_direction,grid_w +15 ,5 );
}
float x_offset, y_offset ;
void noise_img(PImage dst, int max, float ratio_x, float ratio_y) {
noiseSeed((int)random(10000));
for(int x = 0 ; x < dst.width ; x++) {
x_offset += ratio_x ;
for(int y = 0 ; y < dst.height ; y++) {
y_offset += ratio_y ;
float v = map(noise(x_offset,y_offset),0,1,0,max);
v = (int)map(v,0,max,0,g.colorModeX);
int c = color(v,v,v,g.colorModeA) ;
dst.set(x,y,c);
}
}
}
GLSL
#ifdef GL_ES
precision mediump float;
precision mediump int;
#endif
#define PROCESSING_TEXTURE_SHADER
#define PI 3.1415926535897932384626433832795
varying vec4 vertTexCoord;
uniform sampler2D texture;
uniform int mode;
uniform float roof_component_colour;
uniform sampler2D vel_texture;
uniform sampler2D dir_texture;
uniform vec2 wh_ratio;
float map(float value, float start1, float stop1, float start2, float stop2) {
float result = start2 + (stop2 - start2) * ((value - start1) / (stop1 - start1));
return result;
}
vec2 cartesian_coord(float angle) {
float x = cos(angle);
float y = sin(angle);
return vec2(x,y);
}
vec2 translate(float fdir, float fvel) {
float angle_in_radian = map(fdir, 0, roof_component_colour, -PI, PI);
vec2 dir_cart = cartesian_coord(angle_in_radian);
return dir_cart *fvel ;
}
void main() {
vec2 ratio = gl_FragCoord.xy *wh_ratio;
vec4 vel = texture2D(vel_texture, ratio);
vec4 dir = texture2D(dir_texture, ratio);
// rendering picture ;
if(mode == 0) {
float direction = dir.x;
float velocity = vel.x;
vec2 translation = translate(direction,velocity);
// not bad, but totaly wrong
// vec2 coord_dest = vertTexCoord.st +translation
vec2 coord_dest = vertTexCoord.st *ratio +translation ;
// not bad, but totaly wrong
vec2 coord_dest = vertTexCoord.st *ratio +translation ;
vec4 tex_colour = texture2D(texture, coord_dest);
gl_FragColor = tex_colour;
}
// velocity
if(mode == 1 ) {
gl_FragColor = texture2D(vel_texture, vertTexCoord.st);;
}
// direction force field
if(mode == 2) {
gl_FragColor = texture2D(dir_texture, vertTexCoord.st);;
}
}
The texture format is GL_RGBA8, this means each color channel is stored to a byte in, which is a integral data tyoe in rage from 0 to 255.
But when you read texts from the texture sampler, the you will get a floating point value in the range from 0.0 to 1.0. (see glTexImage2D - GL_RGBA).
In the fragment shader you have to map the color channel (in [0, 1]), which you read from the texture sampler, to the range from -PI to PI. For this you can use the GLSL function mix, which does a linear interpolation between 2 values:
vec2 translate(float fdir, float fvel) // fdir, fvel in [0.0, 1.0]
{
float angle = mix(-PI, PI, fdir);
return vec2(cos(angle), sin(angle)) * fvel;
}
The texture coordinates are in range [0, 1]. You have to transform the translation to texture coordinates. For this you have to know the size of your image texture:
vec2 wh_ratio; // 1f/grid_w, 1f/grid_h
vec2 imageTexSize; // size of "texture"
vec2 scale = imageTexSize * wh_ratio;
vec2 coord_dest = vertTexCoord.st + translation / scale;
Thx for the help, now I know the picture size of picture in GLSL :) [0,1], but that's don't work expected, I use the the rendering size or the picture of the must be warp, so in my idea the vec2 imageTexSize is img.widthand img.height is passed from Processing for imageTexSize
uniform vec2 imageTexSize;
.../...
vec2 scale = imageTexSize * wh_ratio;
vec2 coord_dest = vertTexCoord.st + translation / scale;
the result is the top image
and when I try this code
vec2 ratio = gl_FragCoord.xy *wh_ratio;
vec2 coord_dest = vertTexCoord.st +translation / ratio ;
the result is the middle image
and when I try this one
vec2 coord_dest = vertTexCoord.st +translation / wh_ratio ;
the result is the bottom image
Sorry i post a single image because I cannot post more than one pic with my beginner reputation :)
I fix the display bug for the full window display, but now it's the y coord who is reverse for the translation, that's weird because the texture velocity and direction are not reversed in y, the reverse y effect is in the interpretation. that's happened on the 3 mode. I try to reverse coord_dest.y like that
float coord_dest_y = mix(coord_dest.y, vertTexCoord.t, 0);
gl_FragColor = texture2D(texture, vec2(coord_dest.x, coord_dest_y));
but that's change nothing.
I try : float coord_dest_y = mix(coord_dest.y, 0, vertTexCoord.t);but that's make something really strange, so that's don't work too...
here the full the GLSL code
#ifdef GL_ES
precision mediump float;
precision mediump int;
#endif
#define PROCESSING_TEXTURE_SHADER
#define PI 3.1415926535897932384626433832795
varying vec4 vertTexCoord;
uniform sampler2D texture;
uniform int mode;
uniform sampler2D vel_texture;
uniform sampler2D dir_texture;
uniform vec2 wh_grid_ratio;
uniform vec2 wh_renderer_ratio;
vec2 cartesian_coord(float angle) {
float x = cos(angle);
float y = sin(angle);
return vec2(x,y);
}
vec2 translate(float fdir, float fvel) {
//float angle = mix(PI, -PI,fdir);
float angle = mix(fdir, PI, -PI);
return cartesian_coord(angle) *fvel ;
}
void main() {
vec2 ratio = gl_FragCoord.xy *wh_renderer_ratio;
vec4 vel = texture2D(vel_texture, ratio);
vec4 dir = texture2D(dir_texture, ratio);
float direction = dir.x;
float velocity = vel.x;
vec2 translation = translate(direction,velocity);
// mode 0 perfect
// mode 1 interesting
// mode 2 bizarre, but fun
// mode 500 warp image direction
// mode 501 warp image velocity
// perfect
if(mode == 0) {
vec2 scale = gl_FragCoord.xy *wh_renderer_ratio;
vec2 coord_dest = vertTexCoord.st +translation /scale;
float coord_dest_y = mix(coord_dest.y, vertTexCoord.t, 0);
// float coord_dest_y = mix(coord_dest.y, 0, vertTexCoord.t);
gl_FragColor = texture2D(texture, vec2(coord_dest.x, coord_dest_y));
// gl_FragColor = texture2D(texture, coord_dest);
}
// interesting
if(mode == 1) {
vec2 scale = gl_FragCoord.xy *wh_grid_ratio;
vec2 coord_dest = vertTexCoord.st +translation /scale ;
gl_FragColor = texture2D(texture, coord_dest);
}
// bizarre
if(mode == 2) {
vec2 coord_dest = vertTexCoord.st +translation /wh_grid_ratio;
gl_FragColor = texture2D(texture, coord_dest);
}
// velocity
if(mode == 500 ) {
vec4 tex_colour = texture2D(vel_texture, vertTexCoord.st);;
gl_FragColor = tex_colour;
}
// direction force field
if(mode == 501) {
vec4 tex_colour = texture2D(dir_texture, vertTexCoord.st);;
gl_FragColor = tex_colour;
}
}
and the picture result here, to see the cursor error y in the final warping
enter image description here
I need to replace colors of the sprite.
Some example founded in google
Here is I've found a looks like working solution for Unity - [How to Use a Shader to Dynamically Swap a Sprite's Colors][2]
How to port it to cocos2d-x? Can someone please help with code examples?
I'm looking for cocos2d-x v3 code snippet. Really looking forward for some help.
The algorithm in the article How to Use a Shader to Dynamically Swap a Sprite's Colors is very simple. It is based on a one dimensional lookup table with 256 entries. This allows the algorithm to map only 256 different colors.
In detail, the new colors (the colors used to replace) are stored in a one dimensional texture with 256 entries. When a color is read from the original texture a key is used to find the new color in the one dimensional swap texture. The key which is used is the red color channel of the original color, this means that all different colors in the original text must also have different red color values. This is another restriction.
The original document (How to Use a Shader to Dynamically Swap a Sprite's Colors) says:
Note that this may not work as expected if two or more colors on the sprite texture share the same red value! When using this method, it's important to keep the red values of the colors in the sprite texture different.
Further the algorithm mix the original color and the swap color by the alpha channel of the swap color. That causes that the swap color is drawn if the swap color is completely opaque and the original color is drawn if the swap color is completely transparent, in between will be linearly interpolated.
A GLSL function with this algorithm is very short and looks somehow like this:
uniform sampler2D u_spriteTexture; // sprite texture
uniform sampler1D u_swapTexture; // lookup texture with swap colors
vec4 SwapColor( vec2 textureCoord )
{
vec4 originalColor = texture( u_spriteTexture, textureCoord.st );
vec4 swapColor = texture( u_swapTexture, originalColor.r );
vec3 finalColor = mix( originalColor.rgb, swapColor.rgb, swapColor.a );
return vec4( finalColor.rgb, originalColor.a );
}
Suggested Algorithm
Reading the suggested shader from the question, I came up to the following solution. The shader is using an algorithm to convert from RGB to hue, saturation, and value and back. I took this idea and introduced my own thoughts.
Performant conversion functions between RGB and HSV can be found at RGB to HSV/HSL/HCY/HCL in HLSL, which can easily translated from HLSL to GLSL:
RGB to HSV
const float Epsilon = 1e-10;
vec3 RGBtoHCV( in vec3 RGB )
{
vec4 P = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0/3.0) : vec4(RGB.gb, 0.0, -1.0/3.0);
vec4 Q = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
float C = Q.x - min(Q.w, Q.y);
float H = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
return vec3(H, C, Q.x);
}
vec3 RGBtoHSV(in vec3 RGB)
{
vec3 HCV = RGBtoHCV(RGB);
float S = HCV.y / (HCV.z + Epsilon);
return vec3(HCV.x, S, HCV.z);
}
HSV to RGB
vec3 HUEtoRGB(in float H)
{
float R = abs(H * 6.0 - 3.0) - 1.0;
float G = 2.0 - abs(H * 6.0 - 2.0);
float B = 2.0 - abs(H * 6.0 - 4.0);
return clamp( vec3(R,G,B), 0.0, 1.0 );
}
vec3 HSVtoRGB(in vec3 HSV)
{
vec3 RGB = HUEtoRGB(HSV.x);
return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
}
As in the first algorithm of this answer, again a one dimensional lookup table is of need. But the length of the look up table has not to be exactly 256, it is completely user dependent. The key is not the red channel, it is the hue value which is a clear expression of the color and can easily be calculated as seen in RGBtoHSV and RGBtoHSV. The look-up table however has to, contain a color assignment distributed linearly over the * hue * range from 0 to 1 of the original color.
The algorithm can be defined with the following steps:
Convert the original color to the original hue, saturation, and value
Use the original hue as key to find the swap color in the look up table
Convert the swap color to the swap hue, saturation, and value
Convert the hue of the swap color and the original saturation, and value to a new RGB color
Mix the original color and the new color by the alpha channel of the swap color
With this algorithm any RGB color can be swapped, by keeping the saturation and value of the original color. See the following short and clear GLSL function:
uniform sampler2D u_spriteTexture; // sprite texture
uniform sampler1D u_swapTexture; // lookup texture with swap colors
// the texture coordinate is the hue of the original color
vec4 SwapColor( vec2 textureCoord )
{
vec4 originalColor = texture( u_spriteTexture, textureCoord.st );
vec3 originalHSV = RGBtoHSV( originalColor.rgb );
vec4 lookUpColor = texture( u_swapTexture, originalHSV.x );
vec3 swapHSV = RGBtoHSV( lookUpColor.rgb );
vec3 swapColor = HSVtoRGB( vec3( swapHSV.x, originalHSV.y, originalHSV.z ) );
vec3 finalColor = mix( originalColor.rgb, swapColor.rgb, lookUpColor.a );
return vec4( finalColor.rgb, originalColor.a );
}
Apply to cocos2d-x v3.15
To apply the shader to cocos2d-x v3.15 I adapted the HelloWorldScene.h and HelloWorldScene.cpp in the project cpp-empty-test of the cocos2d-x v3.15 test projects.
The shader can be applied to any sprite a can swap up to 10 color tints, but this can easily be expanded. Note, the shader does not only change a single color, it searches all colors which are similar to a color, even the colors with a completely different saturation or brightness. Each color is swapped with a color, that has a equal saturation and brightness, but a new base color.
The information which swaps the colors, is stored in an array of vec3. The x component contains the hue of the original color, the y component contains the hue of the swap color, and the z component contains an epsilon value, which defines the color range.
The shader source files should be placed in the "resource/shader" subdirectory of the project directory.
Vertex shader shader/colorswap.vert
attribute vec4 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
void main()
{
gl_Position = CC_PMatrix * a_position;
cc_FragColor = a_color;
cc_FragTexCoord1 = a_texCoord;
}
Fragment shader shader/colorswap.frag
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
const float Epsilon = 1e-10;
vec3 RGBtoHCV( in vec3 RGB )
{
vec4 P = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0/3.0) : vec4(RGB.gb, 0.0, -1.0/3.0);
vec4 Q = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
float C = Q.x - min(Q.w, Q.y);
float H = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
return vec3(H, C, Q.x);
}
vec3 RGBtoHSV(in vec3 RGB)
{
vec3 HCV = RGBtoHCV(RGB);
float S = HCV.y / (HCV.z + Epsilon);
return vec3(HCV.x, S, HCV.z);
}
vec3 HUEtoRGB(in float H)
{
float R = abs(H * 6.0 - 3.0) - 1.0;
float G = 2.0 - abs(H * 6.0 - 2.0);
float B = 2.0 - abs(H * 6.0 - 4.0);
return clamp( vec3(R,G,B), 0.0, 1.0 );
}
vec3 HSVtoRGB(in vec3 HSV)
{
vec3 RGB = HUEtoRGB(HSV.x);
return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
}
#define MAX_SWAP 10
uniform vec3 u_swap[MAX_SWAP];
uniform int u_noSwap;
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec3 originalHSV = RGBtoHSV( originalColor.rgb );
vec4 swapColor = vec4( originalColor.rgb, 1.0 );
for ( int i = 0; i < 10 ; ++ i )
{
if ( i >= u_noSwap )
break;
if ( abs( originalHSV.x - u_swap[i].x ) < u_swap[i].z )
{
swapColor.rgb = HSVtoRGB( vec3( u_swap[i].y, originalHSV.y, originalHSV.z ) );
break;
}
}
vec3 finalColor = mix( originalColor.rgb, swapColor.rgb, swapColor.a );
gl_FragColor = vec4( finalColor.rgb, originalColor.a );
}
Header file HelloWorldScene.h:
#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__
#include "cocos2d.h"
#define MAX_COLOR 10
class HelloWorld : public cocos2d::Scene
{
public:
virtual bool init() override;
static cocos2d::Scene* scene();
void menuCloseCallback(Ref* sender);
CREATE_FUNC(HelloWorld);
void InitSwapInfo( int i, const cocos2d::Color3B &sourceCol, const cocos2d::Color3B &swapCol, float deviation );
private:
cocos2d::GLProgram* mProgramExample;
cocos2d::Vec3 mSource[MAX_COLOR];
cocos2d::Vec3 mSwap[MAX_COLOR];
float mDeviation[MAX_COLOR];
cocos2d::Vec3 mSwapInfo[MAX_COLOR];
};
#endif // __HELLOWORLD_SCENE_H__
Source file HelloWorldScene.cpp:
Note, the C++ function RGBtoHue and the GLSL function RGBtoHue, should implement the exactly same algorithm.
The input to the function SwapInfo are RGB colors encoded to cocos2d::Vec3. If the source channels of the RGB colors are bytes (unsigned char), then this can easily converted to cocos2d::Vec3 by cocos2d::Vec3( R / 255.0f, G / 255.0f, B / 255.0f ).
#include "HelloWorldScene.h"
#include "AppMacros.h"
USING_NS_CC;
float RGBtoHue( const cocos2d::Vec3 &RGB )
{
const float Epsilon = 1e-10f;
cocos2d::Vec4 P = (RGB.y < RGB.z) ?
cocos2d::Vec4(RGB.y, RGB.z, -1.0f, 2.0f/3.0f) :
cocos2d::Vec4(RGB.y, RGB.z, 0.0f, -1.0f/3.0f);
cocos2d::Vec4 Q = (RGB.x < P.x) ?
cocos2d::Vec4(P.x, P.y, P.w, RGB.x) :
cocos2d::Vec4(RGB.x, P.y, P.z, P.x);
float C = Q.x - (Q.w < Q.y ? Q.w : Q.y);
float H = fabs((Q.w - Q.y) / (6.0f * C + Epsilon) + Q.z);
return H;
}
cocos2d::Vec3 SwapInfo( const cocos2d::Vec3 &sourceCol, const cocos2d::Vec3 &swapCol, float epsi )
{
return cocos2d::Vec3( RGBtoHue( sourceCol ), RGBtoHue( swapCol ), epsi );
}
void HelloWorld::InitSwapInfo( int i, const cocos2d::Color3B &sourceCol, const cocos2d::Color3B &swapCol, float deviation )
{
mSource[i] = cocos2d::Vec3( sourceCol.r/255.0, sourceCol.g/255.0, sourceCol.b/255.0 );
mSwap[i] = cocos2d::Vec3( swapCol.r/255.0, swapCol.g/255.0, swapCol.b/255.0 );
mDeviation[i] = deviation;
mSwapInfo[i] = SwapInfo( mSource[i], mSwap[i], mDeviation[i] );
}
Scene* HelloWorld::scene()
{
return HelloWorld::create();
}
bool HelloWorld::init()
{
if ( !Scene::init() ) return false;
auto visibleSize = Director::getInstance()->getVisibleSize();
auto origin = Director::getInstance()->getVisibleOrigin();
auto closeItem = MenuItemImage::create(
"CloseNormal.png",
"CloseSelected.png",
CC_CALLBACK_1(HelloWorld::menuCloseCallback,this));
closeItem->setPosition(origin + Vec2(visibleSize) - Vec2(closeItem->getContentSize() / 2));
auto menu = Menu::create(closeItem, nullptr);
menu->setPosition(Vec2::ZERO);
this->addChild(menu, 1);
auto sprite = Sprite::create("HelloWorld.png");
sprite->setPosition(Vec2(visibleSize / 2) + origin);
mProgramExample = new GLProgram();
mProgramExample->initWithFilenames("shader/colorswap.vert", "shader/colorswap.frag");
mProgramExample->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_POSITION, GLProgram::VERTEX_ATTRIB_POSITION);
mProgramExample->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_COLOR, GLProgram::VERTEX_ATTRIB_COLOR);
mProgramExample->bindAttribLocation(GLProgram::ATTRIBUTE_NAME_TEX_COORD, GLProgram::VERTEX_ATTRIB_TEX_COORDS);
mProgramExample->link();
mProgramExample->updateUniforms();
mProgramExample->use();
GLProgramState* state = GLProgramState::getOrCreateWithGLProgram(mProgramExample);
sprite->setGLProgram(mProgramExample);
sprite->setGLProgramState(state);
InitSwapInfo( 0, cocos2d::Color3B( 41, 201, 226 ), cocos2d::Color3B( 255, 0, 0 ), 0.1f );
InitSwapInfo( 1, cocos2d::Color3B( 249, 6, 6 ), cocos2d::Color3B( 255, 255, 0 ), 0.1f );
int noOfColors = 2;
state->setUniformVec3v("u_swap", noOfColors, mSwapInfo);
state->setUniformInt("u_noSwap", noOfColors);
this->addChild(sprite);
return true;
}
void HelloWorld::menuCloseCallback(Ref* sender)
{
Director::getInstance()->end();
#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
exit(0);
#endif
}
Compare RGB values instead of Hue
A fragment shader which directly compares RGB colors would look like this:
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
const float Epsilon = 1e-10;
vec3 RGBtoHCV( in vec3 RGB )
{
vec4 P = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0/3.0) : vec4(RGB.gb, 0.0, -1.0/3.0);
vec4 Q = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
float C = Q.x - min(Q.w, Q.y);
float H = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
return vec3(H, C, Q.x);
}
vec3 RGBtoHSV(in vec3 RGB)
{
vec3 HCV = RGBtoHCV(RGB);
float S = HCV.y / (HCV.z + Epsilon);
return vec3(HCV.x, S, HCV.z);
}
vec3 HUEtoRGB(in float H)
{
float R = abs(H * 6.0 - 3.0) - 1.0;
float G = 2.0 - abs(H * 6.0 - 2.0);
float B = 2.0 - abs(H * 6.0 - 4.0);
return clamp( vec3(R,G,B), 0.0, 1.0 );
}
vec3 HSVtoRGB(in vec3 HSV)
{
vec3 RGB = HUEtoRGB(HSV.x);
return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
}
#define MAX_SWAP 10
uniform vec3 u_orig[MAX_SWAP];
uniform vec3 u_swap[MAX_SWAP];
uniform float u_deviation[MAX_SWAP];
uniform int u_noSwap;
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec3 originalHSV = RGBtoHSV( originalColor.rgb );
vec4 swapColor = vec4( originalColor.rgb, 1.0 );
for ( int i = 0; i < 10 ; ++ i )
{
if ( i >= u_noSwap )
break;
if ( all( lessThanEqual( abs(originalColor.rgb - u_orig[i]), vec3(u_deviation[i]) ) ) )
{
vec3 swapHSV = RGBtoHSV( u_swap[i].rgb );
swapColor.rgb = HSVtoRGB( vec3( swapHSV.x, originalHSV.y, originalHSV.z ) );
break;
}
}
vec3 finalColor = mix( originalColor.rgb, swapColor.rgb, swapColor.a );
gl_FragColor = vec4( finalColor.rgb, originalColor.a );
}
Note, the initialization of the uniforms has to be adapt:
int noOfColors = 2;
state->setUniformVec3v("u_orig", noOfColors, mSource);
state->setUniformVec3v("u_swap", noOfColors, mSwap);
state->setUniformFloatv("u_deviation", noOfColors, mDeviation);
state->setUniformInt("u_noSwap", noOfColors);
Extension to the answer
If exactly specified colors should be exchanged, the shader can be much more simplified. For this, the deviations u_deviation have to be restricted (e.g deviation = 0.02;).
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
#define MAX_SWAP 11
uniform vec3 u_orig[MAX_SWAP];
uniform vec3 u_swap[MAX_SWAP];
uniform float u_deviation[MAX_SWAP];
uniform int u_noSwap;
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec4 swapColor = vec4( originalColor.rgb, 1.0 );
for ( int i = 0; i < MAX_SWAP ; ++ i )
{
vec3 deltaCol = abs( originalColor.rgb - u_orig[i] );
float hit = step( deltaCol.x + deltaCol.y + deltaCol.z, u_deviation[i] * 3.0 );
swapColor.rgb = mix( swapColor.rgb, u_swap[i].rgb, hit );
}
gl_FragColor = vec4( swapColor.rgb, originalColor.a );
}
If each color in the source texture has an individual color channel (this means the color value is only use for this special color, e.g. red color channel), then the shader code can be further simplified, because only the one channel has to be compared:
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec4 swapColor = vec4( originalColor.rgb, 1.0 );
for ( int i = 0; i < MAX_SWAP ; ++ i )
{
float hit = step( abs( originalColor.r - u_orig[i].r ), u_deviation[i] );
swapColor.rgb = mix( swapColor.rgb, u_swap[i].rgb, hit );
}
gl_FragColor = vec4( swapColor.rgb, originalColor.a );
}
A further optimization would bring us back to the first algorithm, which was described in this answer. The big advantage of this algorithm would be, that each color is swapped (except the alpha channel of the swap texture is 0), but no expensive searching in the look up table has to be done in the shader.
Each color will be swapped by the corresponding color according to its red color channel. As mentioned, if a color should not be swapped, the alpha channel of the swap texture has to be set to 0.
A new member mSwapTexture has to be add to the class:
cocos2d::Texture2D* mSwapTexture;
The texture can be easily created, and the uniform texture sampler can be set like this:
#include <array>
.....
std::array< unsigned char, 256 * 4 > swapPlane{ 0 };
for ( int c = 0; c < noOfColors; ++ c )
{
size_t i = (size_t)( mSource[c].x * 255.0 ) * 4;
swapPlane[i+0] = (unsigned char)(mSwap[c].x*255.0);
swapPlane[i+1] = (unsigned char)(mSwap[c].y*255.0);
swapPlane[i+2] = (unsigned char)(mSwap[c].z*255.0);
swapPlane[i+3] = 255;
}
mSwapTexture = new Texture2D();
mSwapTexture->setAliasTexParameters();
cocos2d::Size contentSize;
mSwapTexture->initWithData( swapPlane.data(), swapPlane.size(), Texture2D::PixelFormat::RGBA8888, 256, 1, contentSize );
state->setUniformTexture( "u_swapTexture", mSwapTexture );
The fragment shader would look like this:
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
uniform sampler2D u_swapTexture; // lookup texture with 256 swap colors
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec4 swapColor = texture2D(u_swapTexture, vec2(originalColor.r, 0.0));
vec3 finalColor = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
gl_FragColor = vec4(finalColor.rgb, originalColor.a);
}
Of course, the lookup key has not always to be the red channel, any other channel is also possible.
Even a combination of 2 color channels would be possible by using a increased two dimensional lookup texture. See the following example which demonstrates the use of look up texture with 1024 entries. The look up table uses the full red channel (256 indices) in the X dimension and the green channel divided by 64 (4 indices) in the Y dimension.
Create a two dimensional look up table:
std::array< unsigned char, 1024 * 4 > swapPlane{ 0 };
for ( int c = 0; c < noOfColors; ++ c )
{
size_t ix = (size_t)( mSource[c].x * 255.0 );
size_t iy = (size_t)( mSource[c].y * 255.0 / 64.0 );
size_t i = ( iy * 256 + ix ) * 4;
swapPlane[i+0] = (unsigned char)(mSwap[c].x*255.0);
swapPlane[i+1] = (unsigned char)(mSwap[c].y*255.0);
swapPlane[i+2] = (unsigned char)(mSwap[c].z*255.0);
swapPlane[i+3] = 255;
}
mSwapTexture = new Texture2D();
mSwapTexture->setAliasTexParameters();
cocos2d::Size contentSize;
mSwapTexture->initWithData( swapPlane.data(), swapPlane.size(), Texture2D::PixelFormat::RGBA8888, 256, 4, contentSize );
And adapt the fragment shader:
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
vec4 swapColor = texture2D(u_swapTexture, originalColor.rg);
vec3 finalColor = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
gl_FragColor = vec4(finalColor.rgb, originalColor.a);
}
Interpolate the texture
Since it is not possible to use GL_LINEAR with the above approach, this has to be emulated, if it would be of need:
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
uniform sampler2D u_swapTexture; // lookup texture with 256 swap colors
uniform vec2 u_spriteSize;
void main()
{
vec2 texS = 1.0 / u_spriteSize;
vec2 texF = fract( cc_FragTexCoord1 * u_spriteSize + 0.5 );
vec2 texC = (cc_FragTexCoord1 * u_spriteSize + 0.5 - texF) / u_spriteSize;
vec4 originalColor = texture2D(CC_Texture0, texC);
vec4 swapColor = texture2D(u_swapTexture, originalColor.rg);
vec3 finalColor00 = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
originalColor = texture2D(CC_Texture0, texC+vec2(texS.x, 0.0));
swapColor = texture2D(u_swapTexture, originalColor.rg);
vec3 finalColor10 = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
originalColor = texture2D(CC_Texture0, texC+vec2(0.0,texS.y));
swapColor = texture2D(u_swapTexture, originalColor.rg);
vec3 finalColor01 = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
originalColor = texture2D(CC_Texture0, texC+texS.xy);
swapColor = texture2D(u_swapTexture, originalColor.rg);
vec3 finalColor11 = mix(originalColor.rgb, swapColor.rgb, swapColor.a);
vec3 finalColor0 = mix( finalColor00, finalColor10, texF.x );
vec3 finalColor1 = mix( finalColor01, finalColor11, texF.x );
vec3 finalColor = mix( finalColor0, finalColor1, texF.y );
gl_FragColor = vec4(finalColor.rgb, originalColor.a);
}
The new uniform variable u_spriteSize has to be set like this:
auto size = sprite->getTexture()->getContentSizeInPixels();
state->setUniformVec2( "u_spriteSize", Vec2( (float)size.width, (float)size.height ) );
Modify the texture on the CPU
Of course the texture can also be modified on the CPU, but then for each set of swap colors a separated texture has to be generated. the advantage would be that no more shader is of need.
The following code swaps the colors when the texture is loaded. The shader has to be skipped completely.
Sprite * sprite = nullptr;
std::string imageFile = ....;
std::string fullpath = FileUtils::getInstance()->fullPathForFilename(imageFile);
cocos2d::Image *img = !fullpath.empty() ? new Image() : nullptr;
if (img != nullptr && img->initWithImageFile(fullpath))
{
if ( img->getRenderFormat() == Texture2D::PixelFormat::RGBA8888 )
{
unsigned char *plane = img->getData();
for ( int y = 0; y < img->getHeight(); ++ y )
{
for ( int x = 0; x < img->getWidth(); ++ x )
{
size_t i = ( y * img->getWidth() + x ) * 4;
unsigned char t = plane[i];
for ( int c = 0; c < noOfColors; ++ c )
{
if ( fabs(mSource[c].x - plane[i+0]/255.0f) < mDeviation[c] &&
fabs(mSource[c].y - plane[i+1]/255.0f) < mDeviation[c] &&
fabs(mSource[c].z - plane[i+2]/255.0f) < mDeviation[c] )
{
plane[i+0] = (unsigned char)(mSwap[c].x*255.0);
plane[i+1] = (unsigned char)(mSwap[c].y*255.0);
plane[i+2] = (unsigned char)(mSwap[c].z*255.0);
}
}
}
}
}
std::string key = "my_swap_" + imageFile;
if ( Texture2D *texture = _director->getTextureCache()->addImage( img, key ) )
sprite = Sprite::createWithTexture( texture );
}
Combined approach on the CPU and GPU
This approach can be used if always the same regions (colors) of the texture are swapped. The advantage of this approach is, that the original texture is modified only once, but every application of the texture can hold its own swap table.
For this approach the alpha channel is used to hold the index of the swap color. In the example code below, the value range from 1 to including 11 is used to store the indices of the swap color. 0 is reserved for absolute transparency.
Sprite * sprite = nullptr;
std::string imageFile = ....;
std::string key = "my_swap_" + imageFile;
Texture2D *texture = _director->getTextureCache()->getTextureForKey( key );
if (texture == nullptr)
{
std::string fullpath = FileUtils::getInstance()->fullPathForFilename(imageFile);
cocos2d::Image *img = !fullpath.empty() ? new Image() : nullptr;
if ( img->initWithImageFile(fullpath) &&
img->getRenderFormat() == Texture2D::PixelFormat::RGBA8888 )
{
unsigned char *plane = img->getData();
for ( int y = 0; y < img->getHeight(); ++ y )
{
for ( int x = 0; x < img->getWidth(); ++ x )
{
size_t i = ( y * img->getWidth() + x ) * 4;
unsigned char t = plane[i];
for ( int c = 0; c < noOfColors; ++ c )
{
if ( fabs(mSource[c].x - plane[i+0]/255.0f) < mDeviation[c] &&
fabs(mSource[c].y - plane[i+1]/255.0f) < mDeviation[c] &&
fabs(mSource[c].z - plane[i+2]/255.0f) < mDeviation[c] )
{
plane[i+3] = (unsigned char)(c+1);
}
}
}
}
texture = _director->getTextureCache()->addImage( img, key );
}
}
if ( texture != nullptr )
sprite = Sprite::createWithTexture( texture );
The fragment shader needs only the uniforms u_swap and u_noSwap and does not have to do an expensive searching.
#ifdef GL_ES
precision mediump float;
#endif
varying vec4 cc_FragColor;
varying vec2 cc_FragTexCoord1;
#define MAX_SWAP 11
uniform vec3 u_swap[MAX_SWAP];
uniform int u_noSwap;
void main()
{
vec4 originalColor = texture2D(CC_Texture0, cc_FragTexCoord1);
float fIndex = originalColor.a * 255.0 - 0.5;
float maxIndex = float(u_noSwap) + 0.5;
int iIndex = int( clamp( fIndex, 0.0, maxIndex ) );
float isSwap = step( 0.0, fIndex ) * step( fIndex, maxIndex );
vec3 swapColor = mix( originalColor.rgb, u_swap[iIndex], isSwap );
gl_FragColor = vec4( swapColor.rgb, max(originalColor.a, isSwap) );
}
Change the Hue,Saturation,Value of your sprite using shader.
Shader code example:
#ifdef GL_ES
precision mediump float;
#endif
varying vec2 v_texCoord;
////uniform sampler2D CC_Texture0;
uniform float u_dH;
uniform float u_dS;
uniform float u_dL;
//algorithm ref to: https://en.wikipedia.org/wiki/HSL_and_HSV
void main() {
vec4 texColor=texture2D(CC_Texture0, v_texCoord);
float r=texColor.r;
float g=texColor.g;
float b=texColor.b;
float a=texColor.a;
//convert rgb to hsl
float h;
float s;
float l;
{
float max=max(max(r,g),b);
float min=min(min(r,g),b);
//----h
if(max==min){
h=0.0;
}else if(max==r&&g>=b){
h=60.0*(g-b)/(max-min)+0.0;
}else if(max==r&&g<b){
h=60.0*(g-b)/(max-min)+360.0;
}else if(max==g){
h=60.0*(b-r)/(max-min)+120.0;
}else if(max==b){
h=60.0*(r-g)/(max-min)+240.0;
}
//----l
l=0.5*(max+min);
//----s
if(l==0.0||max==min){
s=0.0;
}else if(0.0<=l&&l<=0.5){
s=(max-min)/(2.0*l);
}else if(l>0.5){
s=(max-min)/(2.0-2.0*l);
}
}
//(h,s,l)+(dH,dS,dL) -> (h,s,l)
h=h+u_dH;
s=min(1.0,max(0.0,s+u_dS));
l=l;//do not use HSL model to adjust lightness, because the effect is not good
//convert (h,s,l) to rgb and got final color
vec4 finalColor;
{
float q;
if(l<0.5){
q=l*(1.0+s);
}else if(l>=0.5){
q=l+s-l*s;
}
float p=2.0*l-q;
float hk=h/360.0;
float t[3];
t[0]=hk+1.0/3.0;t[1]=hk;t[2]=hk-1.0/3.0;
for(int i=0;i<3;i++){
if(t[i]<0.0)t[i]+=1.0;
if(t[i]>1.0)t[i]-=1.0;
}//got t[i]
float c[3];
for(int i=0;i<3;i++){
if(t[i]<1.0/6.0){
c[i]=p+((q-p)*6.0*t[i]);
}else if(1.0/6.0<=t[i]&&t[i]<0.5){
c[i]=q;
}else if(0.5<=t[i]&&t[i]<2.0/3.0){
c[i]=p+((q-p)*6.0*(2.0/3.0-t[i]));
}else{
c[i]=p;
}
}
finalColor=vec4(c[0],c[1],c[2],a);
}
//actually, it is not final color. the lightness has not been adjusted
//adjust lightness use the simplest method
finalColor+=vec4(u_dL,u_dL,u_dL,0.0);
gl_FragColor=finalColor;
}
I'm trying to implement Oren-Nayar lighting in the fragment shader as shown here.
However, I'm getting some strange lighting effects on the terrain as shown below.
I am currently sending the shader the 'view direction' uniform as the camera's 'front' vector. I am not sure if this is correct, as moving the camera around changes the artifacts.
Multiplying the 'front' vector by the MVP matrix gives a better result, but the artifacts are still very noticable when viewing the terrain from some angles. It is particularly noticable in dark areas and around the edges of the screen.
What could be causing this effect?
Artifact example
How the scene should look
Vertex Shader
#version 450
layout(location = 0) in vec3 position;
layout(location = 1) in vec3 normal;
out VS_OUT {
vec3 normal;
} vert_out;
void main() {
vert_out.normal = normal;
gl_Position = vec4(position, 1.0);
}
Tesselation Control Shader
#version 450
layout(vertices = 3) out;
in VS_OUT {
vec3 normal;
} tesc_in[];
out TESC_OUT {
vec3 normal;
} tesc_out[];
void main() {
if(gl_InvocationID == 0) {
gl_TessLevelInner[0] = 1.0;
gl_TessLevelInner[1] = 1.0;
gl_TessLevelOuter[0] = 1.0;
gl_TessLevelOuter[1] = 1.0;
gl_TessLevelOuter[2] = 1.0;
gl_TessLevelOuter[3] = 1.0;
}
tesc_out[gl_InvocationID].normal = tesc_in[gl_InvocationID].normal;
gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;
}
Tesselation Evaluation Shader
#version 450
layout(triangles, equal_spacing) in;
in TESC_OUT {
vec3 normal;
} tesc_in[];
out TESE_OUT {
vec3 normal;
float height;
vec4 shadow_position;
} tesc_out;
uniform mat4 model_view;
uniform mat4 model_view_perspective;
uniform mat3 normal_matrix;
uniform mat4 depth_matrix;
vec3 lerp(vec3 v0, vec3 v1, vec3 v2) {
return (
(vec3(gl_TessCoord.x) * v0) +
(vec3(gl_TessCoord.y) * v1) +
(vec3(gl_TessCoord.z) * v2)
);
}
vec4 lerp(vec4 v0, vec4 v1, vec4 v2) {
return (
(vec4(gl_TessCoord.x) * v0) +
(vec4(gl_TessCoord.y) * v1) +
(vec4(gl_TessCoord.z) * v2)
);
}
void main() {
gl_Position = lerp(
gl_in[0].gl_Position,
gl_in[1].gl_Position,
gl_in[2].gl_Position
);
tesc_out.normal = normal_matrix * lerp(
tesc_in[0].normal,
tesc_in[1].normal,
tesc_in[2].normal
);
tesc_out.height = gl_Position.y;
tesc_out.shadow_position = depth_matrix * gl_Position;
gl_Position = model_view_perspective * gl_Position;
}
Fragment Shader
#version 450
in TESE_OUT {
vec3 normal;
float height;
vec4 shadow_position;
} frag_in;
out vec4 colour;
uniform vec3 view_direction;
uniform vec3 light_position;
#define PI 3.141592653589793
void main() {
const vec3 ambient = vec3(0.1, 0.1, 0.1);
const float roughness = 0.8;
const vec4 water = vec4(0.0, 0.0, 0.8, 1.0);
const vec4 sand = vec4(0.93, 0.87, 0.51, 1.0);
const vec4 grass = vec4(0.0, 0.8, 0.0, 1.0);
const vec4 ground = vec4(0.49, 0.27, 0.08, 1.0);
const vec4 snow = vec4(0.9, 0.9, 0.9, 1.0);
if(frag_in.height == 0.0) {
colour = water;
} else if(frag_in.height < 0.2) {
colour = sand;
} else if(frag_in.height < 0.575) {
colour = grass;
} else if(frag_in.height < 0.8) {
colour = ground;
} else {
colour = snow;
}
vec3 normal = normalize(frag_in.normal);
vec3 view_dir = normalize(view_direction);
vec3 light_dir = normalize(light_position);
float NdotL = dot(normal, light_dir);
float NdotV = dot(normal, view_dir);
float angleVN = acos(NdotV);
float angleLN = acos(NdotL);
float alpha = max(angleVN, angleLN);
float beta = min(angleVN, angleLN);
float gamma = dot(view_dir - normal * dot(view_dir, normal), light_dir - normal * dot(light_dir, normal));
float roughnessSquared = roughness * roughness;
float roughnessSquared9 = (roughnessSquared / (roughnessSquared + 0.09));
// calculate C1, C2 and C3
float C1 = 1.0 - 0.5 * (roughnessSquared / (roughnessSquared + 0.33));
float C2 = 0.45 * roughnessSquared9;
if(gamma >= 0.0) {
C2 *= sin(alpha);
} else {
C2 *= (sin(alpha) - pow((2.0 * beta) / PI, 3.0));
}
float powValue = (4.0 * alpha * beta) / (PI * PI);
float C3 = 0.125 * roughnessSquared9 * powValue * powValue;
// now calculate both main parts of the formula
float A = gamma * C2 * tan(beta);
float B = (1.0 - abs(gamma)) * C3 * tan((alpha + beta) / 2.0);
// put it all together
float L1 = max(0.0, NdotL) * (C1 + A + B);
// also calculate interreflection
float twoBetaPi = 2.0 * beta / PI;
float L2 = 0.17 * max(0.0, NdotL) * (roughnessSquared / (roughnessSquared + 0.13)) * (1.0 - gamma * twoBetaPi * twoBetaPi);
colour = vec4(colour.xyz * (L1 + L2), 1.0);
}
First I've plugged your fragment shader into my renderer with my view/normal/light vectors and it works perfectly. So the problem has to be in the way you calculate those vectors.
Next, you say that you set view_dir to your camera's front vector. I assume that you meant "camera's front vector in the world space" which would be incorrect. Since you calculate the dot products with vectors in the camera space, the view_dir must be in the camera space too. That is vec3(0,0,1) would be an easy way to check that. If it works -- we found your problem.
However, using (0,0,1) for the view direction is not strictly correct when you do perspective projection, because the direction from the fragment to the camera then depends on the location of the fragment on the screen. The correct formula then would be view_dir = normalize(-pos) where pos is the fragment's position in camera space (that is with model-view matrix applied without the projection). Further, this quantity now depends only on the fragment location on the screen, so you can calculate it as:
view_dir = normalize(vec3(-(gl_FragCoord.xy - frame_size/2) / (frame_width/2), flen))
flen is the focal length of your camera, which you can calculate as flen = cot(fovx/2).
I know this is a long dead thread, but I've been having the same problem (for several years), and finally found the solution...
It can be partially solved by fixing the orientation of the surface normals to match the polygon winding direction, but you can also get rid of the artifacts in the shader, by changing the following two lines...
float angleVN = acos(cos_nv);
float angleLN = acos(cos_nl);
to this...
float angleVN = acos(clamp(cos_nv, -1.0, 1.0));
float angleLN = acos(clamp(cos_nl, -1.0, 1.0));
Tada!