Merge pull request #21786 from hrydgard/depth-cull-fix

Apply the correct culling epsilons both in fastcull and in software transform

GPU/Common/DrawEngineCommon.cpp

@@ -410,7 +410,11 @@ static bool TestBoundingBoxFast(const float *cullMatrix, const void *vdata, cons
 		Vec4F32 planeDistXY = posXY * planesXY + posW;
 		insideMaskXY |= planeDistXY.CompareGe(Vec4F32::Zero());
 		Vec4F32 posZ = clipPos.ShuffleZZZZ();  // This means that we compute the Z sides twice. Oh well.
-		Vec4F32 planeDistZ = posZ * planesXY + posW;
+		// We need to add the same culling epsilons as when setting up the cull distances in the vertex shader,
+		// so we don't over-cull here. We could also cull looser, but I can't figure out how to do so accurately.
+		// It's a bit unnecessary to take four reciprocals here, let's see if we can avoid that later.
+		Vec4F32 deltaZ = posW.RecipApprox() * 0.0000304f;
+		Vec4F32 planeDistZ = posZ * planesXY + posW + deltaZ;
 		anyOutsideMaskZ |= planeDistZ.CompareLt(Vec4F32::Zero());
 		insideMaskZ |= planeDistZ.CompareGe(Vec4F32::Zero());
 		const float projZ = vpZScale * clipPos[2] / clipPos[3];

GPU/Common/SoftwareTransformCommon.cpp

@@ -737,12 +737,15 @@ static SoftwareTransformAction ProjectClipAndExpand(SoftwareTransformParams &par
 				// First, check inside/outside directions for each index.
 				// We are still in clip space here, so we can cull aggressively in Z.
 				// TODO: This is so cheap now that we can probably avoid the buffer and just do the work below.
+				// See the comment in VertexShader for the epsilons
+
 				for (int i = 0; i < vertexCount; ++i) {
 					float z = transformed[indsIn[i]].z;
 					float w = transformed[indsIn[i]].pos_w;
-					if (z > w) {
+					const float delta = 0.0000304f / w;
+					if (z > w + delta) {
 						outsideZ[i] = 1;
-					} else if (z < -w) {
+					} else if (z < -(w + delta)) {
 						outsideZ[i] = -1;
 					} else {
 						outsideZ[i] = 0;