Hey!
I’m using deferred rendering and my G-buffer contains only the normal map normals, i.e. not the geometry normals.
According to this homepage: Tutorial 16 : Shadow mapping
I can calculate the depth bias with:
float bias = 0.005*tan(acos(cosTheta)); // cosTheta is dot( n,l ), clamped between 0 and 1
bias = clamp(bias, 0,0.01);
Which is a problem in my case, because I don’t have the geometry normals stored in my G-buffer.
I found another thread with a similiar issue here: shadows - Slope scaled depth bias with normal maps - Game Development Stack Exchange
if I understand him correctly then the solution would be(when rendering the shadow map):
float bias = 0.005*tan(acos(geometryNormal, -lightDir));
bias = clamp(bias, 0,0.01);
gl_FragDepth = gl_FragCoord.z - bias; //Write depth to shadow map depth texture.
Is this correct? With this method, should I sample the shadow map depth texture like this(see below)?
shadow2DArray(shadowDepthTexture, vec4(projCoords.xyz, lightDepth)).r;
This is how I setup the depth comparison texture parameters:
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_REF_TO_TEXTURE);
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_COMPARE_FUNC, GL_LEQUAL);
In this case, I must change the current comparison function, i.e. GL_LEQUAL.
If I had the geometry normals to calculate the depth bias then the sampling procedure would be like this:
shadow2DArray(shadowDepthTexture, vec4(projCoords.xyz, lightDepth - bias)).r;