I have implemented the basic shadow mapping algorithm but it works correctly with only one light.
I want to render a scene with two following point lights :
- Light_1 - position : vec3(-8.0f, 5.0f, 8.0f), direction : vec3(1.3f, -1.0f, -1.0f)
- Light_2 - position : vec3(8.0f, 5.0f, 8.0f), direction : vec3(1.3f, -1.0f, -1.0f)
If I render separately the two lights I have the following results:
Rendering with Light_1 :
Rendering with Light_2 :
But the two light together it looks like this :
As you can see the first shadow seems to be rendered correctly, but it is below the shadow of the light_2 which is not correct. To sum up the situation I have the texture of my box which is bound to the texture unit 0. The shadow depth texture is bound from the texture unit 1 and if there are more than one depth texture (so at least two ligths, like in this example), there are bound to the texture unit 1 + 1 (GL_TEXTURE1 + 1). Here's the code that represent what I said :
for (int idy = 0; idy < this->m_pScene->getLightList().size(); idy++)
[...]
Light *light = this->m_pScene->getLightList()[idy];
FrameBuffer *frameBuffer = light->getFrameBuffer();
glActiveTexture(GL_TEXTURE1 + idy);
glBindTexture(GL_TEXTURE_2D, frameBuffer->getTexture()->getTextureId()); //To unbind
shaderProgram->setUniform(std::string("ShadowMatrix[").append(Convertor::toString<int> (idy)).append("]").c_str(), this->m_pScene->getLightList()[idy]->getBiasViewPerspectiveMatrix() * modelMatrix);
shaderProgram->setUniform(std::string("ShadowMap[").append(Convertor::toString<int>(idy)).append("]").c_str(), (int)idy + 1);
It corresponds in our case to :
shaderProgram->setUniform("ShadowMatrix[0]", <shadow_matrix_light_1>);
shaderProgram->setUniform("ShadowMap[0]", 1); (GL_TEXTURE1)
shaderProgram->setUniform("ShadowMatrix[1]", <shadow_matrix_light_2>);
shaderProgram->setUniform("ShadowMap[1]", 2); (GL_TEXTURE2)
The vertex shader is the following (available for just 2 lights):
#version 400
#define MAX_SHADOW_MATRIX 10
#define MAX_SHADOW_COORDS 10
layout (location = 0) in vec4 VertexPosition;
layout (location = 1) in vec3 VertexNormal;
layout (location = 2) in vec2 VertexTexture;
uniform mat3 NormalMatrix;
uniform mat4 ModelViewMatrix;
uniform mat4 ShadowMatrix[MAX_SHADOW_MATRIX];
uniform mat4 MVP;
uniform int lightCount;
out vec3 Position;
out vec3 Normal;
out vec2 TexCoords;
out vec4 ShadowCoords[MAX_SHADOW_COORDS];
void main(void)
{
TexCoords = VertexTexture;
Normal = normalize(NormalMatrix * VertexNormal);
Position = vec3(ModelViewMatrix * VertexPosition);
for (int idx = 0; idx < lightCount; idx++)
ShadowCoords[idx] = ShadowMatrix[idx] * VertexPosition;
gl_Position = MVP * VertexPosition;
}
And a piece of code of the fragment shader :
[...]
vec3 evalBasicFragmentShadow(vec3 LightIntensity, int idx)
{
vec3 Ambient = LightInfos[idx].La * MaterialInfos.Ka;
if (ShadowCoords[idx].w > 0.0f)
{
vec4 tmp_shadow_coords = ShadowCoords[idx];
tmp_shadow_coords.z -= SHADOW_OFFSET;
float shadow = textureProj(ShadowMap[idx], tmp_shadow_coords);
LightIntensity = LightIntensity * shadow + Ambient;
}
else
{
LightIntensity = LightIntensity + MaterialInfos.Ka;
}
return (LightIntensity);
}
vec3 getLightIntensity(vec3 TexColor)
{
vec3 LightIntensity = vec3(0.0f);
for (int idx = 0; idx < lightCount; idx++)
{
vec3 tnorm = (gl_FrontFacing ? -normalize(Normal) : normalize(Normal));
vec3 lightDir = vec3(LightInfos[idx].Position) - Position;
vec3 lightDirNorm = normalize(lightDir);
float lightAtt = getLightAttenuation(lightDir, LightInfos[idx]);
LightIntensity += Point_ADS_Shading(lightAtt, -tnorm, lightDirNorm, TexColor, idx);
LightIntensity = evalBasicFragmentShadow(LightIntensity, idx);
}
return (LightIntensity);
}
[...]
It's look like a texture unit problem because separatly the two shadows have been rendered perfectly and I use glActiveTexture correctly (I think so). Plus, I noticed that if I change the loading order of the lights, the bad shadow is caused by 'the other light' (it's the contrary). So it seems to comes from the texture unit 2, but I don't understand why. Does anyone can help me, please ? Thanks a lot in advance for your help.
