Add slang shaders for additional ray tracing samples

shaders/slang/raytracingpositionfetch/raytracingpositionfetch.slang

@@ -0,0 +1,78 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct Attributes
+{
+    float2 bary;
+};
+
+struct Payload
+{
+    [[vk::location(0)]] float3 hitValue;
+};
+
+RaytracingAccelerationStructure accelStruct;
+RWTexture2D<float4> image;
+struct UBO
+{
+    float4x4 viewInverse;
+    float4x4 projInverse;
+    float4 lightPos;
+};
+ConstantBuffer<UBO> ubo;
+
+[shader("raygeneration")]
+void raygenerationMain()
+{
+    uint3 LaunchID = DispatchRaysIndex();
+    uint3 LaunchSize = DispatchRaysDimensions();
+
+    const float2 pixelCenter = float2(LaunchID.xy) + float2(0.5, 0.5);
+    const float2 inUV = pixelCenter / float2(LaunchSize.xy);
+    float2 d = inUV * 2.0 - 1.0;
+    float4 target = mul(ubo.projInverse, float4(d.x, d.y, 1, 1));
+
+    RayDesc rayDesc;
+    rayDesc.Origin = mul(ubo.viewInverse, float4(0, 0, 0, 1)).xyz;
+    rayDesc.Direction = mul(ubo.viewInverse, float4(normalize(target.xyz), 0)).xyz;
+    rayDesc.TMin = 0.001;
+    rayDesc.TMax = 10000.0;
+
+    Payload payload;
+    TraceRay(accelStruct, RAY_FLAG_FORCE_OPAQUE, 0xff, 0, 0, 0, rayDesc, payload);
+
+    image[int2(LaunchID.xy)] = float4(payload.hitValue, 0.0);
+}
+
+[shader("closesthit")]
+void closesthitMain(inout Payload payload, in Attributes attribs)
+{
+	// We need the barycentric coordinates to calculate data for the current position
+    const float3 barycentricCoords = float3(1.0f - attribs.bary.x - attribs.bary.y, attribs.bary.x, attribs.bary.y);
+
+	// With VK_KHR_ray_tracing_position_fetch we can access the vertices for the hit triangle in the shader
+
+    float3 vertexPos0 = HitTriangleVertexPosition(0);
+    float3 vertexPos1 = HitTriangleVertexPosition(1);
+    float3 vertexPos2 = HitTriangleVertexPosition(2);
+    float3 currentPos = vertexPos0 * barycentricCoords.x + vertexPos1 * barycentricCoords.y + vertexPos2 * barycentricCoords.z;
+
+	// Calcualte the normal from above values
+    float3 normal = normalize(cross(vertexPos1 - vertexPos0, vertexPos2 - vertexPos0));
+    normal = normalize(mul(float4(normal, 1.0), WorldToObject4x3()));
+
+	// Basic lighting
+    float3 lightDir = normalize(ubo.lightPos.xyz - currentPos);
+    float diffuse = max(dot(normal, lightDir), 0.0);
+
+    payload.hitValue.rgb = 0.1 + diffuse;
+}
+
+[shader("miss")]
+void missMain(inout Payload payload)
+{
+    payload.hitValue = float3(0.0, 0.0, 0.2);
+}