Well, I've been wrestling with implementing per-pixel lighting for a few days, and this is essentially the "result" I generally end up with.
I have these hard black spots throughout my mesh, and also those off-kilter dark spots. The blue shading "kind of" works right, except that it applies itself throughout the entire mesh and it appears to apply itself randomly as seen in the image. As I've bound the light to my camera, the light DOES "travel" across the mesh, albeit oddly most of the time. I have no idea why this is happening; my mesh data has normals that, as far as I can tell, are fine (no colour/smoothing issues in MilkShape, 3DS, Lightwave, Blender, Maya etc).
Here's my setup/light code:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
float lpos[4] = {get_cam_pos().x,get_cam_pos().y,get_cam_pos().z,1};
float lamb[4] = {0,0,1,1};
float ldiff[4] = {1,1,0,1};
float lspec[4] = {1,1,0.5,1};
GLfloat lin[4] = {5.0f,5.0f,5.0f,1};
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT0, GL_POSITION, lpos);
glLightfv(GL_LIGHT0, GL_AMBIENT, lamb);
glLightfv(GL_LIGHT0, GL_DIFFUSE, ldiff);
glLightfv(GL_LIGHT0, GL_SPECULAR, lspec);
<from here camera matrix is then loaded and scene is rendered>
And here is my vert shader, from the Lighthouse3D per-pixel-light tutorial:
varying vec4 diffuse,ambientGlobal,ambient, ecPos;
varying vec3 normal,halfVector;
varying float dist;
void main()
{
gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
/* first transform the normal into eye space and normalize the result */
normal = normalize(gl_NormalMatrix * gl_Normal);
/* compute the vertex position in camera space. */
ecPos = gl_ModelViewMatrix * gl_Vertex;
/* Normalize the halfVector to pass it to the fragment shader */
halfVector = gl_LightSource[0].halfVector.xyz;
/* Compute the diffuse, ambient and globalAmbient terms */
diffuse = gl_FrontMaterial.diffuse * gl_LightSource[0].diffuse;
ambient = gl_FrontMaterial.ambient * gl_LightSource[0].ambient;
ambientGlobal = gl_LightModel.ambient * gl_FrontMaterial.ambient;
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}
...and the frag shader, also from the Lighthouse3D tutorial:
uniform sampler2D color_texture;
varying vec4 diffuse,ambientGlobal, ambient, ecPos;
varying vec3 normal,halfVector;
varying float dist;
void main()
{
vec4 tex0Color = vec4(texture2D(color_texture,gl_TexCoord[0].st));
vec3 n,halfV,viewV,lightDir;
float NdotL,NdotHV;
vec4 color = ambientGlobal;
float att;
/* a fragment shader can't write a verying variable, hence we need
a new variable to store the normalized interpolated normal */
n = normalize(normal);
// Compute the ligt direction
lightDir = vec3(gl_LightSource[0].position-ecPos);
/* compute the distance to the light source to a varying variable*/
dist = length(lightDir);
/* compute the dot product between normal and ldir */
NdotL = max(dot(n,normalize(lightDir)),0.0);
if (NdotL > 0.0) {
att = 1.0 / (gl_LightSource[0].constantAttenuation +
gl_LightSource[0].linearAttenuation * dist +
gl_LightSource[0].quadraticAttenuation * dist * dist);
color += att * (diffuse * NdotL + ambient);
halfV = normalize(halfVector);
NdotHV = max(dot(n,halfV),0.0);
color += att * gl_FrontMaterial.specular * gl_LightSource[0].specular
* pow(NdotHV,gl_FrontMaterial.shininess);
}
gl_FragColor = tex0Color*color;
}
Your normals look wrong to me ...
;-)
Related
I implemented a simple shader for the lighting; it kind of works, but the light seems to move when the camera rotates (and only when it rotates).
I'm experimenting with a spotlight, this is how it looks like (it's the spot in the center):
If now I rotate the camera, the spot moves around; for example, here I looked down (I didn't move at all, just looked down) and it seemed at my feet:
I've looked it up and I've seen that it's a common mistake when mixing reference systems in the shader and/or when setting the light's position before moving the camera.
The thing is, I'm pretty sure I'm not doing these two things, but apparently I'm wrong; it's just that I can't find the bug.
Here's the shader:
Vertex Shader
varying vec3 vertexNormal;
varying vec3 lightDirection;
void main()
{
vertexNormal = gl_NormalMatrix * gl_Normal;
lightDirection = vec3(gl_LightSource[0].position.xyz - (gl_ModelViewMatrix * gl_Vertex).xyz);
gl_Position = ftransform();
}
Fragment Shader
uniform vec3 ambient;
uniform vec3 diffuse;
uniform vec3 specular;
uniform float shininess;
varying vec3 vertexNormal;
varying vec3 lightDirection;
void main()
{
vec3 color = vec3(0.0, 0.0, 0.0);
vec3 lightDirNorm;
vec3 eyeVector;
vec3 half_vector;
float diffuseFactor;
float specularFactor;
float attenuation;
float lightDistance;
vec3 normalDirection = normalize(vertexNormal);
lightDirNorm = normalize(lightDirection);
eyeVector = vec3(0.0, 0.0, 1.0);
half_vector = normalize(lightDirNorm + eyeVector);
diffuseFactor = max(0.0, dot(normalDirection, lightDirNorm));
specularFactor = max(0.0, dot(normalDirection, half_vector));
specularFactor = pow(specularFactor, shininess);
color += ambient * gl_LightSource[0].ambient;
color += diffuseFactor * diffuse * gl_LightSource[0].diffuse;
color += specularFactor * specular * gl_LightSource[0].specular;
lightDistance = length(lightDirection[i]);
float constantAttenuation = 1.0;
float linearAttenuation = (0.02 / SCALE_FACTOR) * lightDistance;
float quadraticAttenuation = (0.0 / SCALE_FACTOR) * lightDistance * lightDistance;
attenuation = 1.0 / (constantAttenuation + linearAttenuation + quadraticAttenuation);
// If it's a spotlight
if(gl_LightSource[i].spotCutoff <= 90.0)
{
float spotEffect = dot(normalize(gl_LightSource[0].spotDirection), normalize(-lightDirection));
if (spotEffect > gl_LightSource[0].spotCosCutoff)
{
spotEffect = pow(spotEffect, gl_LightSource[0].spotExponent);
attenuation = spotEffect / (constantAttenuation + linearAttenuation + quadraticAttenuation);
}
else
attenuation = 0.0;
}
color = color * attenuation;
// Moltiplico il colore per il fattore di attenuazione
gl_FragColor = vec4(color, 1.0);
}
Now, I can't show you the code where I render the things, because it's a custom language which integrates opengl and it's designed to create 3D applications (it wouldn't help to show you); but what I do is something like this:
SetupLights();
UpdateCamera();
RenderStuff();
Where:
SetupLights contains actual opengl calls that setup the lights and their positions;
UpdateCamera updates the camera's position using the built-in classes of the language; I don't have much power here;
RenderStuff calls the built-in functions of the language to draw the scene; I don't have much power here either.
So, either I'm doing something wrong in the shader or there's something in the language that "behind the scenes" breaks things.
Can you point me in the right direction?
you wrote
the light's position is already in world coordinates, and that is where I'm doing the computations
however, since you're applying gl_ModelViewMatrix to your vertex and gl_NormalMatrix to your normal, these values are probably in view space, which might cause the moving light.
as an aside, your eye vector looks like it should be in view coordinates, however, view space is a right-handed coordinate system, so "forward" points along the negative z-axis. also, your specular computation will likely be off since you're using the same eye vector for all fragments, but it should probably point towards that fragment's position on the near/far planes.
I'm having some issues with my specular lighting, I have ambient and diffuse but I am now looking at specular to try make a nice looking model.
I have the following in my vertexShader:
#version 330
layout (location = 0) in vec3 Position;
layout (location = 1) in vec3 Normal;
out vec4 Colour0;
// Transforms
uniform mat4 gModelToWorldTransform;
uniform mat4 gWorldToViewToProjectionTransform;
// Ambient light parameters
uniform vec3 gAmbientLightIntensity;
// Directional light parameters
uniform vec3 gDirectionalLightIntensity;
uniform vec3 gDirectionalLightDirection;
// Material constants
uniform float gKa;
uniform float gKd;
uniform float gKs;
uniform float gKsStrength;
void main()
{
// Transform the vertex from local space to homogeneous clip space
vec4 vertexPositionInModelSpace = vec4(Position, 1);
vec4 vertexInWorldSpace = gModelToWorldTransform * vertexPositionInModelSpace;
vec4 vertexInHomogeneousClipSpace = gWorldToViewToProjectionTransform * vertexInWorldSpace;
gl_Position = vertexInHomogeneousClipSpace;
// Calculate the directional light intensity at the vertex
// Find the normal in world space and normalise it
vec3 normalInWorldSpace = (gModelToWorldTransform * vec4(Normal, 0.0)).xyz;
normalInWorldSpace = normalize(normalInWorldSpace);
// Calculate the ambient light intensity at the vertex
// Ia = Ka * ambientLightIntensity
vec4 ambientLightIntensity = gKa * vec4(gAmbientLightIntensity, 1.0);
// Setup the light direction and normalise it
vec3 lightDirection = normalize(-gDirectionalLightDirection);
//lightDirection = normalize(gDirectionalLightDirection);
// Id = kd * lightItensity * N.L
// Calculate N.L
float diffuseFactor = dot(normalInWorldSpace, lightDirection);
diffuseFactor = clamp(diffuseFactor, 0.0, 1.0);
// N.L * light source colour * intensity
vec4 diffuseLightIntensity = gKd * vec4(gDirectionalLightIntensity, 1.0f) * diffuseFactor;
vec3 lightReflect = normalize(reflect(gDirectionalLightDirection, Normal));
//Calculate the specular light intensity at the vertex
float specularFactor = dot(normalInWorldSpace, lightReflect);
specularFactor = pow(specularFactor, gKsStrength);
vec4 specularLightIntensity = gKs * vec4(gDirectionalLightIntensity, 1.0f) * specularFactor;
// Final vertex colour is the product of the vertex colour
// and the total light intensity at the vertex
vec4 colour = vec4(0.0, 1.0, 0.0, 1.0);
Colour0 = colour * (ambientLightIntensity + diffuseLightIntensity + specularLightIntensity);
}
Then in my main.cpp I have the some code to try and get this working together, the specular light is definitely doing something, only, rather than making the model look shiny, it seems to intensify the light to the point where I can't see any details.
I create the following variables:
// Lighting uniforms location
GLuint gAmbientLightIntensityLoc;
GLuint gDirectionalLightIntensityLoc;
GLuint gDirectionalLightDirectionLoc;
GLuint gSpecularLightIntensityLoc;
// Materials uniform location
GLuint gKaLoc;
GLuint gKdLoc;
GLuint gKsLoc;
GLuint gKsStrengthLoc;
I then set my variables like so in the renderSceneCallBack() function which is called in the main:
// Set the material properties
glUniform1f(gKaLoc, 0.2f);
glUniform1f(gKdLoc, 0.9f);
glUniform1f(gKsLoc, 0.5f);
glUniform1f(gKsStrengthLoc, 0.5f);
I then create a initLights() function which I would like to handle all lighting, this is also called in the main:
static void initLights()
{
// Setup the ambient light
vec3 ambientLightIntensity = vec3(0.2f, 0.2f, 0.2f);
glUniform3fv(gAmbientLightIntensityLoc, 1, &ambientLightIntensity[0]);
// Setup the direactional light
vec3 directionalLightDirection = vec3(0.0f, 0.0f, -1.0f);
normalize(directionalLightDirection);
glUniform3fv(gDirectionalLightDirectionLoc, 1, &directionalLightDirection[0]);
vec3 directionalLightIntensity = vec3(0.8f, 0.8f, 0.8f);
glUniform3fv(gDirectionalLightIntensityLoc, 1, &directionalLightIntensity[0]);
//Setup the specular Light
vec3 specularLightIntensity = vec3(0.5f, 0.5f, 0.5f);
glUniform3fv(gSpecularLightIntensityLoc, 1, &specularLightIntensity[0]);
}
Can anyone see what I might be doing wrong, I could have some of the calculatiuons wrong and I just don't see it. Both the ambient/diffuse lighting are working correctly. This photo illustrates whats currently happening, ambient on the left, diffuse in the middle and specular with strength set to 30 on the right.
Answer
I forgot to pass this value into the main:
gKsStrengthLoc = glGetUniformLocation(shaderProgram, "gKsStrength");
//assert(gDirectionalLightDirectionLoc != 0xFFFFFFFF);
Everything works now using the answer selected
Your value for gKsStrength looks way too small:
glUniform1f(gKsStrengthLoc, 0.5f);
This value controls how shiny the object is, with higher values making it more shiny. This makes sense if you look at the calculation in the shader:
specularFactor = pow(specularFactor, gKsStrength);
The larger the exponent, the faster the value drops off, which means that the specular highlight becomes more narrow.
Typical values might be something like 10.0f for moderately shiny, 30.0f for quite shiny, and even higher for very shiny materials.
With your value of 0.5f, you get a very wide specular "highlight". Your value for the specular intensity is also fairly high (0.5), so the highlight is going to cover most of the object, and saturate the colors for large parts.
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 tried to incorporate attentuation, but it failed does nothing.
I have diffuse, ambient, and specular lighting working. I just need to dim the light as the fragments get further away from the light.
Also, i have the attenuation parameter for my light:
glLightf(GL_LIGHT0, GL_QUADRATIC_ATTENUATION, 0.0004f);
This is the floor lighting, the light is positioned just behind the cube:
http://oi43.tinypic.com/i39fuo.jpg
.vert
varying vec3 N;
varying vec3 v;
varying vec3 c;
varying float dist;
void main(void)
{
vec4 ecPos;
vec3 aux;
ecPos = gl_ModelViewMatrix * gl_Vertex;
aux = vec3(gl_LightSource[0].position-ecPos);
dist = length(aux);
c = vec3(gl_Color);
v = vec3(gl_ModelViewMatrix * gl_Vertex);
N = normalize(gl_NormalMatrix * gl_Normal);
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}
.frag
varying vec3 N;
varying vec3 v;
varying vec3 c;
varying float dist;
void main (void)
{
float att;
att = 1.0 / (gl_LightSource[0].constantAttenuation +
gl_LightSource[0].linearAttenuation * dist +
gl_LightSource[0].quadraticAttenuation * dist * dist);
vec3 L = normalize(gl_LightSource[0].position.xyz - v);
vec3 E = normalize(-v); // we are in Eye Coordinates, so EyePos is (0,0,0)
vec3 R = normalize(-reflect(L,N));
float nDotL = max(dot(N,L), 0.0);
float rDotE = max(dot(R,E),0.0);
float power = pow(rDotE, gl_FrontMaterial.shininess);
//calculate Ambient Term:
vec4 Iamb = gl_FrontLightProduct[0].ambient * att;
//calculate Diffuse Term:
vec4 Idiff = gl_FrontLightProduct[0].diffuse * nDotL * att;
Idiff = clamp(Idiff, 0.0, 1.0);
// calculate Specular Term:
vec4 Ispec = gl_FrontLightProduct[0].specular * power * att;
Ispec = clamp(Ispec, 0.0, 1.0);
// write Total Color:
gl_FragColor = Iamb + Idiff + Ispec + c;
}
From this image i cant' really see anything. How about setting a small object as lightsource.
Which object's use this shader?
Some things that come to my mind:
You normalized your normal in your vertex shader, which is an unnecessary step.
Passed vectors from vertex to fragment shader must be normalized inside fragment shader since they will be interpolated.
Aslong you don't do any length based calculations in your vertex shader, which you aren't no normalization is necessary in vertex shader.
You should normalize the normal in fragment shader, then you don't need to normalize your reflect vector.
Attenuation is not based on anything "complex" calculated in shader. So output it and then check the rest. How does your diffuse term looks like?
Further hints:
You could place the light vector and attenuation calculation inside vertex shader and pass it as to fragment shader (pack it in a 4 vec component) to save interpolators.
the final specular clamp is unecessary, the values should be within [0, 1] range automatically. If not you have a problem.
Pixel based lighting is a common issue in many OpenGL applications, as the standard OpenGL lighting has very poor quality.
I want to use a GLSL program to have per-pixel based lighting in my OpenGL program instead of per-vertex. Just Diffuse lighting, but with fog, texture and texture-alpha at least.
I started with this shader:
texture.vert:
varying vec3 position;
varying vec3 normal;
void main(void)
{
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
gl_FrontColor = gl_Color;
gl_TexCoord[0] = gl_MultiTexCoord0;
normal = normalize(gl_NormalMatrix * gl_Normal);
position = vec3(gl_ModelViewMatrix * gl_Vertex);
}
texture.frag:
uniform sampler2D Texture0;
uniform int ActiveLights;
varying vec3 position;
varying vec3 normal;
void main(void)
{
vec3 lightDir;
float attenFactor;
vec3 eyeDir = normalize(-position); // camera is at (0,0,0) in ModelView space
vec4 lightAmbientDiffuse = vec4(0.0,0.0,0.0,0.0);
vec4 lightSpecular = vec4(0.0,0.0,0.0,0.0);
// iterate all lights
for (int i=0; i<ActiveLights; ++i)
{
// attenuation and light direction
if (gl_LightSource[i].position.w != 0.0)
{
// positional light source
float dist = distance(gl_LightSource[i].position.xyz, position);
attenFactor = 1.0/( gl_LightSource[i].constantAttenuation +
gl_LightSource[i].linearAttenuation * dist +
gl_LightSource[i].quadraticAttenuation * dist * dist );
lightDir = normalize(gl_LightSource[i].position.xyz - position);
}
else
{
// directional light source
attenFactor = 1.0;
lightDir = gl_LightSource[i].position.xyz;
}
// ambient + diffuse
lightAmbientDiffuse += gl_FrontLightProduct[i].ambient*attenFactor;
lightAmbientDiffuse += gl_FrontLightProduct[i].diffuse * max(dot(normal, lightDir), 0.0) * attenFactor;
// specular
vec3 r = normalize(reflect(-lightDir, normal));
lightSpecular += gl_FrontLightProduct[i].specular *
pow(max(dot(r, eyeDir), 0.0), gl_FrontMaterial.shininess) *
attenFactor;
}
// compute final color
vec4 texColor = gl_Color * texture2D(Texture0, gl_TexCoord[0].xy);
gl_FragColor = texColor * (gl_FrontLightModelProduct.sceneColor + lightAmbientDiffuse) + lightSpecular;
float fog = (gl_Fog.end - gl_FogFragCoord) * gl_Fog.scale; // Intensität berechnen
fog = clamp(fog, 0.0, 1.0); // Beschneiden
gl_FragColor = mix(gl_Fog.color, gl_FragColor, fog); // Nebelfarbe einmischen
}
Comments are german because it's a german site where this code was posted, sorry.
But all this shader does is make everything very dark. No lighting effects at all - yet the shader codes compile. If I only use GL_LIGHT0 in the fragment shader, then it seems to work, but only reasonable for camera facing polygons and my floor polygon is just extremely dark. Also quads with RGBA textures show no sign of transparency.
I use standard glRotate/Translate for the Modelview matrix, and glVertex/Normal for my polygons. OpenGL lighting works fine apart from the fact that it looks ugly on very large surfaces. I triple checked my normals, they are fine.
Is there something wrong in the above code?
OR
Tell me why there is no generic lighting Shader for this actual task (point based light with distance falloff: a candle if you will) - shouldn't there be just one correct way to do this? I don't want bump/normal/parallax/toon/blur/whatever effects. I just want my lighting to perform better with larger polygons.
All Tutorials I found are only useful for lighting a single object when the camera is at 0,0,0 facing orthogonal to the object. The above is the only one found that at least looks like the thing I want to do.
I would strongly suggest you to read this article to see how the standard ADS lightning is done within GLSL.That is GL 4.0 but not a problem to adjust to your version:
Also you operate in the view (camera) space so DON"T negate the eyes vector :
vec3 eyeDir = normalize(-position);
I had pretty similar issues to yours because I also negated the eye vector forgetting that it is transformed into the view space.Your diffuse and specular calculations seem to be wrong too in the current scenario.In your place I wouldn't use data from the fixed pipeline at all ,otherwise what is the point doing it in a shader?
Here is the method to calculate diffuse and specular in the per fragment ADS point lightning:
void ads( int lightIndex,out vec3 ambAndDiff, out vec3 spec )
{
vec3 s = vec3(lights[lightIndex].Position - posOut) ;
vec3 v = normalize( posOut.xyz );
vec3 n = normalize(normOut);
vec3 h = normalize(v+s) ;// half vector (read in the web on what it is )
vec3 diffuse = ((Ka+ lights[lightIndex].Ld) * Kd * max( 0.0,dot(n, v) )) ;
spec = Ks * pow( max(0.0, dot(n,h) ), Shininess ) ;
ambAndDiff = diffuse ;
/// Ka-material ambient factor
/// Kd-material diffuse factor
/// Ks-material specular factor.
/// lights[lightIndex].Ld-lights diffuse factor;you may also add La and Ls if you want to have even more control of the light shading.
}
Also I wouldn't suggest you using the attenuation equation you have here,it is hard to control.If you want to add light radius based attenuation
there is this nice blog post: