I expect to be spamming the link from now on though!So Bungie can render atmosphere with a continuous transition into space... now why would they need such a capability?
http://www.youtube.com/watch?v=aFnbhQU0lcY
float ComputeEVSM( float2 vShadowMapUVs, float fReceiverDepth, float fCascadeIndex ) {
//depth should be 0 to 1 range.
float2 warpedDepth = WarpDepth(fReceiverDepth);
float posDepth = warpedDepth.x;
float negDepth = warpedDepth.y;
float4 occluder = tCascadeShadowMaps.Sample( sShadowLinearClamp, float3( vShadowMapUVs, fCascadeIndex ));
float2 posMoments = occluder.xz;
float2 negMoments = occluder.yw;
// compute derivative of the warping function at depth of pixel and use it to scale min
// variance
float posDepthScale = fESMExponentialMultiplier * posDepth;
float posMinVariance = VSM_MIN_VARIANCE * posDepthScale * posDepthScale;
float negDepthScale = fESMExponentialMultiplier2 * negDepth;
float negMinVariance = VSM_MIN_VARIANCE * negDepthScale * negDepthScale;
//compute two Chebyshev bounds, one for positive and one for negative, and takes the
// minimum
float shadowContrib1= ComputeChebyshevBound(posMoments.x, posMoments.y, posDepth, posMinVariance);
float shadowContrib2= ComputeChebyshevBound(negMoments.x, negMoments.y, negDepth, negMinVariance);
return min(shadowContrib1, shadowContrib2);
}Yup. The other exp functions are run when rendering the ESMs themselves (either during the rendering of the shadowmaps or their post processing).
// Input depth should be in [0, 1]
float2 WarpDepth(float depth, float2 exponents)
{
// Rescale depth into [-1, 1]
depth = 2.0f * depth - 1.0f;
float pos = exp( exponents.x * depth);
float neg = -exp(-exponents.y * depth);
return float2(pos, neg);
}OUT.Color.xy = WarpDepth(...);
OUT.Color.z = OUT.Color.x*OUT.Color.x;
OUT.Color.w = OUT.Color.y*OUT.Color.y;Yes.
Just blur it normally. The log-space filtering stuff is mainly useful in the context of ESM, where the fp32 range isn't really large enough to bump your exponents up high enough for large scenes.
Even in the case of using EVSM ?
#define g_fShadowExponentialPos 40.0f
#define g_fShadowExponentialNeg 20.0f
float2 WarpDepth(float depth, float fExponentPos, float fExponentNeg)
{
// Rescale depth into [-1, 1]
//depth = 2.0f * depth - 1.0f; // commented out otherwise shadow is even larger ??!
float pos = exp(fExponentPos * depth);
float neg = -exp(-fExponentNeg * depth);
return float2(pos, neg);
}OUT.Color.xy = WarpDepth(fDepthAdj, g_fShadowExponentialPos, g_fShadowExponentialNeg);
OUT.Color.z = OUT.Color.x*OUT.Color.x;
OUT.Color.w = OUT.Color.y*OUT.Color.y;float4 occluder = oShadowTexture.Sample(SamplerShadowMap, vProjCoords[iSplit].xyz);
float2 warpedDepth = WarpDepth(fDepthAdj, g_fShadowExponentialPos, g_fShadowExponentialNeg);
float posDepth = warpedDepth.x;
float negDepth = warpedDepth.y;
float2 posMoments = occluder.xz;
float2 negMoments = occluder.yw;
// compute derivative of the warping function at depth of pixel and use it to scale min
// variance
float posDepthScale = g_fShadowExponentialPos * posDepth;
float posMinVariance = g_VSMMinVariance[iSplit] * posDepthScale * posDepthScale;
float negDepthScale = g_fShadowExponentialNeg * negDepth;
float negMinVariance = g_VSMMinVariance[iSplit] * negDepthScale * negDepthScale;
// compute two Chebyshev bounds, one for positive and one for negative, and takes the
// minimum
float shadowContrib1 = ChebyshevUpperBound(posMoments, posDepth, posMinVariance);
float shadowContrib2 = ChebyshevUpperBound(negMoments, negDepth, negMinVariance);
fShadowContrib = min(shadowContrib1, shadowContrib2);
As per Bungie's presentation, I mean mapping it such that the [0, 1] range covers just the bits of the depth range that are visible in the camera frusta. i.e. everything outside the current partition should get clamped to 0 or 1 (depending on which side of the frusta it is relative to the light).
