The problem
I'm trying to make shaders for my game. In the fragment shaders, I don't want to set the color of the fragment but add to it. How do I do so? I'm new to this, so sorry for any mistakes.
The code
varying vec3 vN;
varying vec3 v;
varying vec4 color;
#define MAX_LIGHTS 1
void main (void)
{
vec3 N = normalize(vN);
vec4 finalColor = vec4(0.0, 0.0, 0.0, 0.0);
for (int i=0;i<MAX_LIGHTS;i++)
{
vec3 L = normalize(gl_LightSource[i].position.xyz - v);
vec3 E = normalize(-v); // we are in Eye Coordinates, so EyePos is (0,0,0)
vec3 R = normalize(-reflect(L,N));
vec4 Iamb = gl_LightSource[i].ambient;
vec4 Idiff = gl_LightSource[i].diffuse * max(dot(N,L), 0.0);
Idiff = clamp(Idiff, 0.0, 1.0);
vec4 Ispec = gl_LightSource[i].specular * pow(max(dot(R,E),0.0),0.3*gl_FrontMaterial.shininess);
Ispec = clamp(Ispec, 0.0, 1.0);
finalColor += Iamb + Idiff + Ispec;
}
gl_FragColor = color * finalColor ;
}
Thanks in advance!
You can not get the color of the fragment you're writing to. In simple scenarios (like yours) what you can do is to enable blending and set the blending functions to achieve additive blending.
For more complex logic you'd create a framebuffer object, attach a texture to it, render your input(e.g. scene) to that texture, then switch to and render with another framebuffer(or the default "screen" one), this way you can sample your scene from the texture and add the lighting on top. Read how to do this in detail on WebGLFundamentals.com
Related
I'm trying to do point source directional lighting in OpenGL using my textbooks examples. I'm showing a rectangle centered at the origin, and doing the lighting computations in the shader. The rectangle appears, but it is black even when I try to put colored lights on it. Normals for the rectangle are all (0, 1.0, 0). I'm not doing any non-uniform scaling, so the regular model view matrix should also transform the normals.
I have code that sets the light parameters(as uniforms) and material parameters(also as uniforms) for the shader. There is no per vertex color information.
void InitMaterial()
{
color material_ambient = color(1.0, 0.0, 1.0);
color material_diffuse = color(1.0, 0.8, 0.0);
color material_specular = color(1.0, 0.8, 0.0);
float material_shininess = 100.0;
// set uniforms for current program
glUniform3fv(glGetUniformLocation(Programs[lightingType], "materialAmbient"), 1, material_ambient);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "materialDiffuse"), 1, material_diffuse);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "materialSpecular"), 1, material_specular);
glUniform1f(glGetUniformLocation(Programs[lightingType], "shininess"), material_shininess);
}
For the lights:
void InitLight()
{
// need light direction and light position
point4 light_position = point4(0.0, 0.0, -1.0, 0.0);
color light_ambient = color(0.2, 0.2, 0.2);
color light_diffuse = color(1.0, 1.0, 1.0);
color light_specular = color(1.0, 1.0, 1.0);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "lightPosition"), 1, light_position);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "lightAmbient"), 1, light_ambient);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "lightDiffuse"), 1, light_diffuse);
glUniform3fv(glGetUniformLocation(Programs[lightingType], "lightSpecular"), 1, light_specular);
}
The fragment shader is a simple pass through shader that sets the color to the one input from the vertex shader. Here is the vertex shader :
#version 150
in vec4 vPosition;
in vec3 vNormal;
out vec4 color;
uniform vec4 materialAmbient, materialDiffuse, materialSpecular;
uniform vec4 lightAmbient, lightDiffuse, lightSpecular;
uniform float shininess;
uniform mat4 modelView;
uniform vec4 lightPosition;
uniform mat4 projection;
void main()
{
// Transform vertex position into eye coordinates
vec3 pos = (modelView * vPosition).xyz;
vec3 L = normalize(lightPosition.xyz - pos);
vec3 E = normalize(-pos);
vec3 H = normalize(L + E);
// Transform vertex normal into eye coordinates
vec3 N = normalize(modelView * vec4(vNormal, 0.0)).xyz;
// Compute terms in the illumination equation
vec4 ambient = materialAmbient * lightAmbient;
float Kd = max(dot(L, N), 0.0);
vec4 diffuse = Kd * materialDiffuse * lightDiffuse;
float Ks = pow(max(dot(N, H), 0.0), shininess);
vec4 specular = Ks * materialSpecular * lightSpecular;
if(dot(L, N) < 0.0) specular = vec4(0.0, 0.0, 0.0, 1.0);
gl_Position = projection * modelView * vPosition;
color = ambient + diffuse + specular;
color.a = 1.0;
}
Ok, it's working now. The solution was to replace glUniform3fv with glUniform4fv, I guess because the glsl counterpart is a vec4 instead of a vec3. I thought that it would be able to recognize this and simply add a 1.0 to the end, but no.
I am currently working on a particle system in which each particle is a point. I am using shaders to color the particles. I would like the particle to change colors based on its position. However, when I try to include an extra vector variable in my fragment and vertex shaders, my shaders do not compile.
Fragment shader:
varying vec3 normal;
varying vec3 vertex_to_light_vector;
varying vec3 vertex_to_eye_vector;
//out vec3 color;
//varying float red;
//varying float green;
//varying float blue;
//black body radiation color map
void main ()
{
const vec4 AmbientColor = vec4(0.2, 0.2, 0.2, 0.2);
const vec4 DiffuseColor = vec4(0.0, 0.1,0.3, 0.1);
const vec4 SpecularColor = vec4(1.0, 1.0, 1.0, 0.1);
vec3 normalized_normal = normalize(normal);
vec3 normalized_vertex_to_light_vector = normalize(vertex_to_light_vector);
vec3 normalized_vertex_to_eye_vector = normalize(vertex_to_eye_vector);
vec3 bisector = normalize(vertex_to_light_vector + vertex_to_eye_vector);
float DiffuseTerm = clamp(max(0.0, dot(normalized_normal, normalized_vertex_to_light_vector)), 0.0, 1.0);
float SpecularTerm = clamp(max(0.0, dot(normalized_normal, bisector)), 0.0, 1.0);
gl_FragColor = DiffuseColor * DiffuseTerm;
//+ SpecularColor * pow(SpecularTerm, 80.0);
}
Vertex shader:
varying vec3 normal;
varying vec3 vertex_to_light_vector;
varying vec3 vertex_to_eye_vector;
//out vec3 color;
//varying float red;
//varying float green;
//varying float blue;
//varying vec2 texture_coordinate;
//uniform sample2D my_color_texture;
void main ()
{
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; //gettingfinal position in projection space
if (gl_Position[0] > 0.5){
// color = vec3(1.0, 0.0, 0.0);
// red =1.0;
// green = 0.0;
// blue = 0.0;
}
else {
// color = vec3(0.0, 0.0, 1.0);
// color[0] = 0.0;
// color[1] = 0.0;
// color[2] = 1.0;
// red = 0.0;
// green = 0.0;
// blue = 1.0;
}
normal = gl_NormalMatrix * gl_Normal;
vec4 vertex_in_modelView_space = gl_ModelViewMatrix * gl_Vertex;
vertex_to_light_vector = vec3(gl_LightSource[0].position - vertex_in_modelView_space);
vertex_to_eye_vector = vec3(-vertex_in_modelView_space);
//texture_coordinate = vec2(gl_MultiTexCoord0);
}
Since your shader does not contain a #version directive on the first line, a compliant GLSL compiler is supposed to treat your shader as GLSL 1.1. This creates a serious problem with your color output, because the in and out qualifiers were not valid for varying declarations prior to OpenGL 3.0 (GLSL 1.3).
More than likely what is actually happening is that the compiler is encountering out and this is generating a parse error. Use varying instead, since these GLSL shaders are implicitly #version 110.
Even if the shaders were written using #version 130, you have another issue that will prevent successful I/O between the vertex shader and fragment shader after linking. Vertex shader outputs are fragment shader inputs, thus your color variable would need to be declared: out vec3 color in the vertex shader and in vec3 color in the fragment shader. But again, this only applies to modern OpenGL shaders written against the OpenGL 3.0 GLSL spec. (GLSL 130) or newer.
For future reference, if you were to call glGetShaderInfoLog (...) after attempting to compile your shaders, it would inform you of the parse error. Likewise, glGetProgramInfoLog (...) will give you any linker errors after you call glLinkProgram (...) or glValidateProgram (...).
i have been trying to implement deferred rendering for past 2 weeks. I have finally come to the spot lighting pass part using stencil buffer and linearized depth. I hold 3 framebuffer textures : albedo, normal+depth (X,Y,Z,EyeViewLinearDepth), Lighting texture. So I draw my light (sphere) and apply this fragment shader :
void main(void)
{
vec2 texCoord = gl_FragCoord.xy * u_inverseScreenSize.xy;
float linearDepth = texture2D(u_normalDepth, texCoord.st).a;
// vector to far plane
vec3 viewRay = vec3(v_vertex.xy * (-farClip/v_vertex.z), -farClip);
// scale viewRay by linear depth to get view space position
vec3 vertex = viewRay * linearDepth;
vec3 normal = texture2D(u_normalDepth, texCoord.st).xyz*2.0 - 1.0;
vec4 ambient = vec4(0.0, 0.0, 0.0, 1.0);
vec4 diffuse = vec4(0.0, 0.0, 0.0, 1.0);
vec4 specular = vec4(0.0, 0.0, 0.0, 1.0);
vec3 lightDir = lightpos - vertex ;
vec3 R = normalize(reflect(lightDir, normal));
vec3 V = normalize(vertex);
float lambert = max(dot(normal, normalize(lightDir)), 0.0);
if (lambert > 0.0) {
float distance = length(lightDir);
if (distance <= u_lightRadius) {
//CLASSICAL LIGHTING COMPUTATION PART
}
}
vec4 final_color = vec4(ambient + diffuse + specular);
gl_FragColor = vec4(final_color.xyz, 1.0);
}
The variables you need to know : v_vertex is eye space position of the vertex (of sphere), lightpos is the position/center of the light in eye space, linearDepth is generated on geometry pass stage in eye space.
The problem is that, the code fail this if check : if (distance <= u_lightRadius). The light is never computed until i remove the distance check. I am sure that i pass these values correctly, radius is 170.0, light position is only like 40-50 units away from the model. There is definitely something wrong but i can't find it somehow. I tried many possibilities of radius and other variables.
I'm working on some basic lighting in my application, and am unable to get a simple light to work (so far..).
Here's the vertex shader:
#version 150 core
uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
uniform mat4 pvmMatrix;
uniform mat3 normalMatrix;
in vec3 in_Position;
in vec2 in_Texture;
in vec3 in_Normal;
out vec2 textureCoord;
out vec4 pass_Color;
uniform LightSources {
vec4 ambient = vec4(0.5, 0.5, 0.5, 1.0);
vec4 diffuse = vec4(0.5, 0.5, 0.5, 1.0);
vec4 specular = vec4(0.5, 0.5, 0.5, 1.0);
vec4 position = vec4(1.5, 7, 0.5, 1.0);
vec4 direction = vec4(0.0, -1.0, 0.0, 1.0);
} lightSources;
struct Material {
vec4 ambient;
vec4 diffuse;
vec4 specular;
float shininess;
};
Material mymaterial = Material(
vec4(1.0, 0.8, 0.8, 1.0),
vec4(1.0, 0.8, 0.8, 1.0),
vec4(1.0, 0.8, 0.8, 1.0),
0.995
);
void main() {
gl_Position = pvmMatrix * vec4(in_Position, 1.0);
textureCoord = in_Texture;
vec3 normalDirection = normalize(normalMatrix * in_Normal);
vec3 lightDirection = normalize(vec3(lightSources.direction));
vec3 diffuseReflection = vec3(lightSources.diffuse) * vec3(mymaterial.diffuse) * max(0.0, dot(normalDirection, lightDirection));
/*
float bug = 0.0;
bvec3 result = equal( diffuseReflection, vec3(0.0, 0.0, 0.0) );
if(result[0] && result[1] && result[2]) bug = 1.0;
diffuseReflection.x += bug;
*/
pass_Color = vec4(diffuseReflection, 1.0);
}
And here's the fragment shader:
#version 150 core
uniform sampler2D texture;
in vec4 pass_Color;
in vec2 textureCoord;
void main() {
vec4 out_Color = texture2D(texture, textureCoord);
gl_FragColor = pass_Color;
//gl_FragColor = out_Color;
}
I'm rendering a textured wolf to the screen as a test. If I change the fragment shader to use out_Color, I see the wolf rendered properly. If I use the pass_Color, I see nothing on the screen.
This is what the screen looks like when I use out_Color in the fragment shader:
I know the diffuseReflection vector is full of 0's, by uncommenting this code in the vertex shader:
...
/*
float bug = 0.0;
bvec3 result = equal( diffuseReflection, vec3(0.0, 0.0, 0.0) );
if(result[0] && result[1] && result[2]) bug = 1.0;
diffuseReflection.x += bug;
*/
...
This will make the x component of the diffuseReflection vector 1.0, which turns the wolf red.
Does anyone see anything obvious I'm doing wrong here?
As suggested in the comments, try debugging incrementally. I see a number of ways your shader could be wrong. Maybe your normalMatrix isn't being passed properly? Maybe your in_Normal isn't mapped to the appropriate input? Maybe when you're casting lightSources.direction to a vec3, the compiler's doing something funky? Maybe your shader isn't even running at all, but you think it is? Maybe you have geometry or tessellation units and it's not passing correctly?
No one really has a chance of answering this correctly. As for me, it looks fine--but again, any of the factors above could happen--and probably more.
To debug this, you need to break it down. As suggested in the comments, try rendering the normals. Then, you should try rendering the light direction. Then render your n dot l term. Then multiply by your material parameters, then by your texture. Somewhere along the way you'll figure out the problem. As an additional tip, change your clear color to something other than black so that any black-rendered objects stand out.
It's worth noting that the above advice--break it down--is applicable to all things debugging, not just shaders. As I see it, you haven't done so here.
i want to shade the quad with checkers:
f(P)=[floor(Px)+floor(Py)]mod2.
My quad is:
glBegin(GL_QUADS);
glVertex3f(0,0,0.0);
glVertex3f(4,0,0.0);
glVertex3f(4,4,0.0);
glVertex3f(0,4, 0.0);
glEnd();
The vertex shader file:
varying float factor;
float x,y;
void main(){
x=floor(gl_Position.x);
y=floor(gl_Position.y);
factor = mod((x+y),2.0);
}
And the fragment shader file is:
varying float factor;
void main(){
gl_FragColor = vec4(factor,factor,factor,1.0);
}
But im getting this:
It seems that the mod function doeasn't work or maybe somthing else...
Any help?
It is better to calculate this effect in fragment shader, something like that:
vertex program =>
varying vec2 texCoord;
void main(void)
{
gl_Position = vec4(gl_Vertex.xy, 0.0, 1.0);
gl_Position = sign(gl_Position);
texCoord = (vec2(gl_Position.x, gl_Position.y)
+ vec2(1.0)) / vec2(2.0);
}
fragment program =>
#extension GL_EXT_gpu_shader4 : enable
uniform sampler2D Texture0;
varying vec2 texCoord;
void main(void)
{
ivec2 size = textureSize2D(Texture0, 0);
float total = floor(texCoord.x * float(size.x)) +
floor(texCoord.y * float(size.y));
bool isEven = mod(total, 2.0) == 0.0;
vec4 col1 = vec4(0.0, 0.0, 0.0, 1.0);
vec4 col2 = vec4(1.0, 1.0, 1.0, 1.0);
gl_FragColor = (isEven) ? col1 : col2;
}
Output =>
Good luck!
Try this function in your fragment shader:
vec3 checker(in float u, in float v)
{
float checkSize = 2;
float fmodResult = mod(floor(checkSize * u) + floor(checkSize * v), 2.0);
float fin = max(sign(fmodResult), 0.0);
return vec3(fin, fin, fin);
}
Then in main you can call it using :
vec3 check = checker(fs_vertex_texture.x, fs_vertex_texture.y);
And simply pass x and y you are getting from vertex shader. All you have to do after that is to include it when calculating your vFragColor.
Keep in mind that you can change chec size simply by modifying checkSize value.
What your code does is calculate the factor 4 times (once for each vertex, since it's vertex shader code) and then interpolate those values (because it's written into a varying varible) and then output that variable as color in the fragment shader.
So it doesn't work that way. You need to do that calculation directly in the fragment shader. You can get the fragment position using the gl_FragCoord built-in variable in the fragment shader.
May I suggest the following:
float result = mod(dot(vec2(1.0), step(vec2(0.5), fract(v_uv * u_repeat))), 2.0);
v_uv is a vec2 of UV values,
u_repeat is a vec2 of how many times the pattern should be repeated for each axis.
result is 0 or 1, you can use it in mix function to provide colors, for example:
gl_FragColor = mix(vec4(1.0, 1.0, 1.0, 1.0), vec4(0.0, 0.0, 0.0, 1.0) result);
Another nice way to do it is by just tiling a known pattern (zooming out). Assuming that you have a square canvas:
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
// Normalized pixel coordinates (from 0 to 1)
vec2 uv = fragCoord/iResolution.xy;
uv -= 0.5; // moving the coordinate system to middle of screen
// Output to screen
fragColor = vec4(vec3(step(uv.x * uv.y, 0.)), 1.);
}
Code above gives you this kind of pattern.
Code below by just zooming 4.5 times and taking the fractional part repeats the pattern 4.5 times resulting in 9 squares per row.
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
// Normalized pixel coordinates (from 0 to 1)
vec2 uv = fract(fragCoord/iResolution.xy * 4.5);
uv -= 0.5; // moving the coordinate system to middle of screen
// Output to screen
fragColor = vec4(vec3(step(uv.x * uv.y, 0.)), 1.);
}