In my deferred renderer, I've managed to successfully reconstruct my fragment position from the depth buffer.... mostly. By comparing my results to the position stored in an extra buffer, I've noticed that I'm getting a lot of popping far away from the screen. Here's a screenshot of what I'm seeing:
The green and yellow parts at the top are just the skybox, where the position buffer contains (0, 0, 0) but the reconstruction algorithm interprets it as a normal fragment with depth = 0.0 (or 1.0?).
The scene is rendered using fragColor = vec4(0.5 + (reconstPos - bufferPos.xyz), 1.0);, so anywhere that the resulting fragment is exactly (0.5, 0.5, 0.5) is where the reconstruction and the buffer have the exact same value. Imprecision towards the back of the depth buffer is to be expected, but that magenta and blue seems a bit strange.
This is how I reconstruct the position from the depth buffer:
vec3 reconstructPositionWithMat(vec2 texCoord)
{
float depth = texture2D(depthBuffer, texCoord).x;
depth = (depth * 2.0) - 1.0;
vec2 ndc = (texCoord * 2.0) - 1.0;
vec4 pos = vec4(ndc, depth, 1.0);
pos = matInvProj * pos;
return vec3(pos.xyz / pos.w);
}
Where texCoord = gl_FragCoord.xy / textureSize(colorBuffer, 0);, and matInvProj is the inverse of the projection matrix used to render the gbuffer.
Right now my position buffer is GL_RGBA32F (since it's only for testing accuracy, I don't care as much about bandwith and memory waste), and my depth buffer is GL_DEPTH24_STENCIL8 (I got similar results from GL_DEPTH_COMPONENT32, and yes I do need the stencil buffer).
My znear is 0.01f, and zfar is 1000.0f. I'm rendering a single quad as my ground which is 2000.0f x 2000.0f large (I wanted it to be big enough that it would clip with the far plane).
Is this level of imprecision considered acceptable? What are some ways that people have gotten around this problem? Is there something wrong with how I reconstruct the view/eye-space position?
