I've messed around ALOT with depth bias, and I'm convinced that bias is not where the issue lies. I've also tried culling and not culling the front faces, though the effects are even less accurate. I've also tried using 'CLAMP' instead of 'BORDER', though it doesn't fix the issue and it adds a 'stretching' problem.
This is the code to project the shadow map:
sampler2D vSamSMaps[1] =
{
sampler_state
{
Texture = <gvShadowTexture>;
MinFilter = POINT;
MagFilter = POINT;
MipFilter = POINT;
AddressU = BORDER;
AddressV = BORDER;
}
};
/**
@brief Calculate the single source shadows for the light source provided
@param fvLVPPos, the position of the pixel in light's view projection * world matrix
@param fvLIndex, the light's index*/
float CalcShadows( float4 fvLVPPos, int fvLIndex )
{
//Project the texture coords and scale/offset to [0, 1].
float4 tvProjTex = fvLVPPos;
tvProjTex.xy /= tvProjTex.w;
tvProjTex.x = 0.5f * tvProjTex.x + 0.5f;
tvProjTex.y = -0.5f * tvProjTex.y + 0.5f;
// Compute pixel depth for shadowing.
float tvDepth = tvProjTex.z / tvProjTex.w;
// Transform to texel space ( NOTE: SMAP_SIZE HARDCODED TO 1024 FOR NOW )
float2 tvTexelpos = SMAP_SIZE * tvProjTex.xy;
// Determine the lerp amounts.
float2 tvLerps = frac( tvTexelpos );
// 2x2 percentage closest filter.
float dx = 1.0f / SMAP_SIZE;
float s0 = step(tvDepth, tex2D(vSamSMaps[fvLIndex], tvProjTex.xy).r + SHADOW_EPSILON);
float s1 = step(tvDepth, tex2D(vSamSMaps[fvLIndex], tvProjTex.xy + float2(dx, 0.0f)).r + SHADOW_EPSILON);
float s2 = step(tvDepth, tex2D(vSamSMaps[fvLIndex], tvProjTex.xy + float2(0.0f, dx)).r + SHADOW_EPSILON);
float s3 = step(tvDepth, tex2D(vSamSMaps[fvLIndex], tvProjTex.xy + float2(dx, dx)).r + SHADOW_EPSILON);
return lerp( lerp( s0, s1, tvLerps.x ),
lerp( s2, s3, tvLerps.x ),
tvLerps.y );
}
