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o3de/Gems/Atom/Feature/Common/Assets/Shaders/Reflections/ReflectionProbeBlendWeight....

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/*
* Copyright (c) Contributors to the Open 3D Engine Project.
* For complete copyright and license terms please see the LICENSE at the root of this distribution.
*
* SPDX-License-Identifier: Apache-2.0 OR MIT
*
*/
// Specular IBL reflection pipeline:
// Stencil -> BlendWeight -> GlobalFullscreen -> RenderOuter -> RenderInner -> Composite
// -----------
//
// This shader writes the blend weight of a particular probe to this location in the blend
// weight texture. This is an additive operation since other overlapping probes will write
// their blend weights here as well. Note that this shader only considers pixels stenciled
// to the outer volumes. Inner volumes always blend at 100% so there is no need to write them
// to the blend weight texture.
#include <scenesrg.srgi>
#include <viewsrg.srgi>
#include "ReflectionProbeRenderObjectSrg.azsli"
ShaderResourceGroup PassSrg : SRG_PerPass
{
Texture2DMS<float> m_depth;
}
#include "ReflectionCommon.azsli"
// Vertex Shader
struct VSInput
{
float3 m_position : POSITION;
};
struct VSOutput
{
float4 m_position : SV_Position;
};
VSOutput MainVS(VSInput vsInput)
{
VSOutput OUT;
float3 positionWS = mul(ObjectSrg::GetWorldMatrix(), float4(vsInput.m_position, 1.0)).xyz;
OUT.m_position = mul(ViewSrg::m_viewProjectionMatrix, float4(positionWS, 1.0));
return OUT;
}
// Pixel Shader
struct PSOutput
{
float m_blendWeight : SV_Target0;
};
PSOutput MainPS(VSOutput IN, in uint sampleIndex : SV_SampleIndex)
{
// reconstruct world position from depth
// Note: this is the world position of the rendered object covered by the volume, not the volume itself
float3 positionWS = ReconstructWorldPositionFromDepth(IN.m_position.xy, sampleIndex).xyz;
// make sure the pixel belongs to this probe volume
// this is necessary since it could have the correct stencil value but actually reside
// in another volume that's in between the camera and the volume we're rendering
if (!ObbContainsPoint(ObjectSrg::GetWorldMatrixInverse(), ObjectSrg::m_outerObbHalfLengths, positionWS))
{
discard;
}
// determine blend based on position with respect to the inner and outer AABBs
// if it's inside the inner AABB it blends at 100%, otherwise it's the percentage of the distance between the inner/outer AABB
float blendWeight = 1.0f;
if (!ObbContainsPoint(ObjectSrg::GetWorldMatrixInverse(), ObjectSrg::m_innerObbHalfLengths, positionWS))
{
// not inside the inner AABB, so it's in between the inner and outer AABBs
// compute blend amount based on the distance to the outer AABB
blendWeight = ComputeLerpBetweenInnerOuterOBBs(
ObjectSrg::GetWorldMatrixInverse(),
ObjectSrg::m_innerObbHalfLengths,
ObjectSrg::m_outerObbHalfLengths,
positionWS);
}
// write the blend weight (additive) at this position for the probe volume
PSOutput OUT;
OUT.m_blendWeight = blendWeight;
return OUT;
}