UnityCACAO-HDRP17/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/Shadows/RayTracingContactShadow.raytrace

// We need only need one bounce given that we want to see the if there is anything that occludes the area light
#pragma max_recursion_depth 1

// Given that this pass does not use the shadow algorithm multi-compile, we need to define SHADOW_LOW to quite the shadow algorithm error
#define SHADOW_LOW

// Required for contact shadows
#define USE_FPTL_LIGHTLIST

// We are using DX12 here
#define SHADER_TARGET 50
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Macros.hlsl"
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/ShaderPass/ShaderPass.cs.hlsl"
#define SHADERPASS SHADERPASS_RAYTRACING
#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Packing.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariablesFunctions.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/Lighting.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoopDef.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/Shadow/ContactShadows.hlsl"

// Raytracing includes
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/ShaderVariablesRaytracing.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/RayTracingCommon.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/RaytracingIntersection.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/RaytracingSampling.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/Common/RayTracingHelpers.hlsl"

// The target acceleration structure that we will evaluate the reflexion in
TEXTURE2D_X(_DepthTexture);

[shader("miss")]
void MissShaderShadows(inout RayIntersectionVisibility rayIntersection : SV_RayPayload)
{
    rayIntersection.color = float3(1.0, 1.0, 1.0);
}

bool RayTraceContactShadow(PositionInputs posInput, float3 direction)
{
    if (_ContactShadowLength > 0.0f)
    {
        //Here LightDirection is not the light direction but the light position
        float rayLength = _ContactShadowLength;

        // Evaluate the ray bias
        float rayBias = EvaluateRayTracingBias(posInput.positionWS);
    
        // Create the ray descriptor for this pixel
        RayDesc rayDescriptor;
        rayDescriptor.Origin = posInput.positionWS + rayBias * direction;
        rayDescriptor.Direction = direction;
        rayDescriptor.TMin = 0.0;
        rayDescriptor.TMax = rayLength - rayBias;

        // Adjust world-space position to match the RAS setup with XR single-pass and camera relative
        ApplyCameraRelativeXR(rayDescriptor.Origin);

        // Create and init the RayIntersectionVisibility structure for this
        RayIntersectionVisibility rayIntersection;
        rayIntersection.color = float3(0.0, 0.0, 0.0);
        rayIntersection.pixelCoord = posInput.positionSS;

        // Evaluate the ray visibility term and PDF
        TraceRay(_RaytracingAccelerationStructure, RAY_FLAG_CULL_FRONT_FACING_TRIANGLES | RAY_FLAG_SKIP_CLOSEST_HIT_SHADER | RAY_FLAG_ACCEPT_FIRST_HIT_AND_END_SEARCH, RAYTRACINGRENDERERFLAG_CAST_SHADOW, 0, 1, 0, rayDescriptor, rayIntersection);
        
        // Not sure true translates to 1 in every compiler
        return (rayIntersection.color.x == 0.0) ? 1 : 0;
    }
    return 0;
}

[shader("raygeneration")]
void RayGenContactShadows()
{
    // Grab the dimensions of the current raytrace shader
    uint3 LaunchIndex = DispatchRaysIndex();
    uint3 LaunchDim = DispatchRaysDimensions();

    UNITY_XR_ASSIGN_VIEW_INDEX(LaunchIndex.z);

    // Get the current pixel coordinate
    uint2 pixelCoord = uint2(LaunchIndex.x, LaunchIndex.y);

    // Fetch the current depth value
    float depth = LOAD_TEXTURE2D_X(_DepthTexture, pixelCoord).x;

    // Reconstruction world space position
    uint2 tileIndex = pixelCoord / GetTileSize();
    PositionInputs posInput = GetPositionInput(pixelCoord.xy, _ScreenSize.zw, depth, UNITY_MATRIX_I_VP, GetWorldToViewMatrix(), tileIndex);

    // discard the shadow if we're on the sky or outside of the contact shadow range
    if (depth == UNITY_RAW_FAR_CLIP_VALUE || posInput.linearDepth - _ContactShadowFadeEnd > 1)
        return;

    float fade = 0.0;
    // store the 24 bit contact shadow mask mask (1: pixel is in contact shadow, 0: pixel is not shadowed)
    uint contactShadowMask = 0;
    UnpackContactShadowData(_ContactShadowTextureUAV[COORD_TEXTURE2D_X(pixelCoord)], fade, contactShadowMask);

	for (int i = 0; i < _DirectionalLightCount; ++i)
    {
        DirectionalLightData light = _DirectionalLightDatas[i];

        if (light.contactShadowMask != 0 && light.isRayTracedContactShadow == 1.0)
        {
            // We store the inverse of the contact shadow:
            bool occluded = RayTraceContactShadow(posInput, -light.forward);

            // light.contactShadowMask contains one bit at the position of the contact shadow index that will
            // be tested in the lightloop, so it insert 1 at the index of the contact shadow if there is a contact shadow
            // we take full bits at one multiplied by contact shadow and filter the bit at the contact shadow index.
            contactShadowMask |= (light.contactShadowMask * occluded);
        }
    }
    uint lightCount, lightStart;

#ifndef LIGHTLOOP_DISABLE_TILE_AND_CLUSTER
    GetCountAndStart(posInput, LIGHTCATEGORY_PUNCTUAL, lightStart, lightCount);
#else   // LIGHTLOOP_DISABLE_TILE_AND_CLUSTER
    lightCount = _PunctualLightCount;
    lightStart = 0;
#endif

    uint v_lightListOffset = 0;
    uint v_lightIdx = lightStart;
    while (v_lightListOffset < lightCount)
    {
        v_lightIdx = FetchIndex(lightStart, v_lightListOffset);
        LightData s_lightData = FetchLight(v_lightIdx);
        v_lightListOffset++;
        if (s_lightData.contactShadowMask != 0 && s_lightData.isRayTracedContactShadow == 1.0)
        {
            // Compute light ray direction:
            float3 direction = normalize(s_lightData.positionRWS.xyz - posInput.positionWS);

            bool occluded = RayTraceContactShadow(posInput, direction);

            // light.contactShadowMask contains one bit at the position of the contact shadow index that will
            // be tested in the lightloop, so it insert 1 at the index of the contact shadow if there is a contact shadow
            // we take full bits at one multiplied by contact shadow and filter the bit at the contact shadow index.
            contactShadowMask |= (s_lightData.contactShadowMask * occluded);
        }
    }

    _ContactShadowTextureUAV[COORD_TEXTURE2D_X(pixelCoord)] = PackContactShadowData(fade, contactShadowMask);
}