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Seele/res/shaders/DepthCullingTask.slang
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import Common;
import Scene;
groupshared MeshPayload p;
groupshared uint head;
groupshared MeshData mesh;
groupshared InstanceData instance;
groupshared Frustum viewFrustum;
groupshared float4x4 modelViewProjection;
struct DepthData
{
Texture2D<float> texture;
RWStructuredBuffer<float> buffer;
}
ParameterBlock<DepthData> pDepthAttachment;
[numthreads(TASK_GROUP_SIZE, 1, 1)]
[shader("amplification")]
void taskMain(
uint threadID: SV_GroupThreadID,
uint groupID: SV_GroupID, )
{
if (threadID == 0)
{
head = 0;
instance = pScene.instances[pOffsets.instanceOffset + groupID];
mesh = pScene.meshData[pOffsets.instanceOffset + groupID];
p.instanceId = pOffsets.instanceOffset + groupID;
p.meshletOffset = mesh.meshletOffset;
p.cullingOffset = pScene.cullingOffsets[p.instanceId];
modelViewProjection = mul(mul(pViewParams.projectionMatrix, pViewParams.viewMatrix), instance.transformMatrix);
float3 origin = viewToModel(instance.inverseTransformMatrix, float4(0, 0, 0, 1)).xyz;
const float offset = 0.0f;
float3 corners[4] = {
screenToModel(instance.inverseTransformMatrix, float4(offset, offset, -1.0f, 1.0f)).xyz,
screenToModel(instance.inverseTransformMatrix, float4(pViewParams.screenDimensions.x - offset, offset, -1.0f, 1.0f)).xyz,
screenToModel(instance.inverseTransformMatrix, float4(offset, pViewParams.screenDimensions.y - offset, -1.0f, 1.0f)).xyz,
screenToModel(instance.inverseTransformMatrix, float4(pViewParams.screenDimensions - float2(offset, offset), -1.0f, 1.0f)).xyz
};
viewFrustum.sides[0] = computePlane(origin, corners[2], corners[0]);
viewFrustum.sides[1] = computePlane(origin, corners[1], corners[3]);
viewFrustum.sides[2] = computePlane(origin, corners[0], corners[1]);
viewFrustum.sides[3] = computePlane(origin, corners[3], corners[2]);
}
GroupMemoryBarrierWithGroupSync();
for (uint i = threadID; i < mesh.numMeshlets; i += TASK_GROUP_SIZE)
{
uint m = p.meshletOffset + i;
uint cull = p.cullingOffset + i;
MeshletDescription meshlet = pScene.meshletInfos[m];
MeshletCullingInfo culling = pScene.cullingInfos[cull];
// if any triangle was visible last frame, it was drawn by the cached pass already
if(!culling.wasVisible())
{
// if the meshlet is outside of the frustum, we skip it since we cant do depth culling anyways
if(meshlet.bounding.insideFrustum(viewFrustum))
{
uint2 mipDimensions = uint2((uint(pViewParams.screenDimensions.x) + BLOCK_SIZE - 1) / BLOCK_SIZE, (uint(pViewParams.screenDimensions.y) + BLOCK_SIZE - 1) / BLOCK_SIZE);
// now we calculate what mip level we need to only sample up to 4 texels covering the entire meshlet
uint2 screenCornerMin = mipDimensions;
uint2 screenCornerMax = uint2(0, 0);
// we use reverse depth, so higher values are closer
float maxDepth = 0;
{
float4 corners[8];
corners[0] = float4(meshlet.bounding.min.x, meshlet.bounding.min.y, meshlet.bounding.min.z, 1.0f);
corners[1] = float4(meshlet.bounding.min.x, meshlet.bounding.min.y, meshlet.bounding.max.z, 1.0f);
corners[2] = float4(meshlet.bounding.min.x, meshlet.bounding.max.y, meshlet.bounding.min.z, 1.0f);
corners[3] = float4(meshlet.bounding.min.x, meshlet.bounding.max.y, meshlet.bounding.max.z, 1.0f);
corners[4] = float4(meshlet.bounding.max.x, meshlet.bounding.min.y, meshlet.bounding.min.z, 1.0f);
corners[5] = float4(meshlet.bounding.max.x, meshlet.bounding.min.y, meshlet.bounding.max.z, 1.0f);
corners[6] = float4(meshlet.bounding.max.x, meshlet.bounding.max.y, meshlet.bounding.min.z, 1.0f);
corners[7] = float4(meshlet.bounding.max.x, meshlet.bounding.max.y, meshlet.bounding.max.z, 1.0f);
for(uint i = 0; i < 8; ++i)
{
float4 clipCorner = mul(modelViewProjection, corners[i]);
float4 screenCorner = clipToScreen(clipCorner) / BLOCK_SIZE;
screenCornerMin = uint2(min(screenCornerMin.x, uint(screenCorner.x)), min(screenCornerMin.y, uint(screenCorner.y)));
screenCornerMax = uint2(max(screenCornerMax.x, uint(screenCorner.x)), max(screenCornerMax.y, uint(screenCorner.y)));
maxDepth = max(maxDepth, screenCorner.z);
}
}
uint mipOffset = 0;
// in theory this wouldnt work if no corner was in screen, as min would be greater that max, however we verified that with view culling
while(screenCornerMax.x - screenCornerMin.x > 1 || screenCornerMax.y - screenCornerMin.y > 1)
{
mipOffset += mipDimensions.x * mipDimensions.y;
mipDimensions = uint2(mipDimensions.x + 1, mipDimensions.y + 1) / 2;
screenCornerMin /= 2;
screenCornerMax /= 2;
}
// now we sample 4 texels from the depth at the calculated mip level, this should give us the screen extent of the meshlet
float d1 = pDepthAttachment.buffer[mipOffset + (screenCornerMin.y * mipDimensions.x) + screenCornerMin.x];
float d2 = pDepthAttachment.buffer[mipOffset + (screenCornerMin.y * mipDimensions.x) + screenCornerMax.x];
float d3 = pDepthAttachment.buffer[mipOffset + (screenCornerMax.y * mipDimensions.x) + screenCornerMin.x];
float d4 = pDepthAttachment.buffer[mipOffset + (screenCornerMax.y * mipDimensions.x) + screenCornerMax.x];
// we want to check if the minimum depth (the value farthest away) is smaller than the maximum bounding box depth
// otherwise, there is no way for the meshlet to be visible
float d = min(min(d1, d2), min(d3, d4));
// this is technically not correct, as the mipmap is generated with a linear filter, but we actually would need a min filter, but whatever
if(d < maxDepth)
{
uint index;
InterlockedAdd(head, 1, index);
p.culledMeshlets[index] = i;
}
}
}
}
GroupMemoryBarrierWithGroupSync();
DispatchMesh(head, 1, 1, p);
}