Added sample for VK_KHR_ray_tracing_position_fetch

shaders/glsl/raytracingpositionfetch/closesthit.rchit

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+/* Copyright (c) 2024, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+#version 460
+#extension GL_EXT_ray_tracing : enable
+#extension GL_EXT_nonuniform_qualifier : enable
+// This extension is required for fetching position data in the closes hit shader
+#extension GL_EXT_ray_tracing_position_fetch : require
+
+layout(location = 0) rayPayloadInEXT vec3 hitValue;
+hitAttributeEXT vec2 attribs;
+
+layout(binding = 2, set = 0) uniform UBO 
+{
+	mat4 viewInverse;
+	mat4 projInverse;
+	vec4 lightPos;
+} ubo;
+
+void main()
+{
+	// We need the barycentric coordinates to calculate data for the current position
+	const vec3 barycentricCoords = vec3(1.0 - attribs.x - attribs.y, attribs.x, attribs.y);
+
+	// With VK_KHR_ray_tracing_position_fetch we can access the vertices for the hit triangle in the shader
+	vec3 vertexPos0 = gl_HitTriangleVertexPositionsEXT[0];
+	vec3 vertexPos1 = gl_HitTriangleVertexPositionsEXT[1];
+	vec3 vertexPos2 = gl_HitTriangleVertexPositionsEXT[2];
+	vec3 currentPos = vertexPos0 * barycentricCoords.x + vertexPos1 * barycentricCoords.y + vertexPos2 * barycentricCoords.z;
+
+	// Calcualte the normal from above values
+	vec3 normal = normalize(cross(vertexPos1 - vertexPos0, vertexPos2 - vertexPos0));
+	normal = normalize(vec3(normal * gl_WorldToObjectEXT));
+
+	// Visualize the normal
+	hitValue = normal;
+
+	// Basic lighting
+	vec3 lightDir = normalize(ubo.lightPos.xyz - currentPos);
+	float diffuse = max(dot(normal, lightDir), 0.0);
+
+	hitValue = vec3(0.1 + diffuse);
+}