Update ray tracing samples to use VK_KHR_ray_tracing (#753)

* Started updating ray tracing samples to KHR extension

* Updated GLSL shaders to use GL_EXT_ray_tracing

* Code cleanup, naming

* Fix include directories to use Vulkan headers from repository instead of NDK for the Android build

* Added new Android function pointers

* Renamed basic ray tracing sample

Added android build files

* Remove unused batch file

* Replaced remaining NV identifiers

* Updating ray tracing shadow sample to KHR extension

* Updated shaders to use KHR instead of NV extension

Fixed shader bindings

* Updating ray tracing reflections sample to KHR extension

* Renamed ray tracing reflections sample

* Renamed ray tracing shadows sample

Added android build files

* Removed no-longer used batch files for shader generation

* Proper alignment for the shader binding table

* Updated readme

* Reworked shader group setup

* Cleanup

* Reworked shader group setup

* Reworked shader group setup

* Code cleanup

data/shaders/hlsl/raytracingshadows/closesthit.rchit

@@ -0,0 +1,85 @@
+// Copyright 2020 Google LLC
+
+struct InPayload
+{
+	[[vk::location(0)]] float3 hitValue;
+};
+
+struct InOutPayload
+{
+	[[vk::location(2)]] bool shadowed;
+};
+
+RaytracingAccelerationStructure topLevelAS : register(t0);
+struct UBO
+{
+	float4x4 viewInverse;
+	float4x4 projInverse;
+	float4 lightPos;
+	int vertexSize;
+};
+cbuffer ubo : register(b2) { UBO ubo; };
+
+StructuredBuffer<float4> vertices : register(t3);
+StructuredBuffer<uint> indices : register(t4);
+
+struct Vertex
+{
+  float3 pos;
+  float3 normal;
+  float2 uv;
+  float4 color;
+  float4 _pad0; 
+  float4 _pad1;
+};
+
+Vertex unpack(uint index)
+{
+	// Unpack the vertices from the SSBO using the glTF vertex structure
+	// The multiplier is the size of the vertex divided by four float components (=16 bytes)
+	const int m = ubo.vertexSize / 16;
+
+	float4 d0 = vertices[m * index + 0];
+	float4 d1 = vertices[m * index + 1];
+	float4 d2 = vertices[m * index + 2];
+
+	Vertex v;
+	v.pos = d0.xyz;
+	v.normal = float3(d0.w, d1.x, d1.y);
+	v.color = float4(d2.x, d2.y, d2.z, 1.0);
+
+	return v;
+}
+
+[shader("closesthit")]
+void main(in InPayload inPayload, inout InOutPayload inOutPayload, in float3 attribs)
+{
+	uint PrimitiveID = PrimitiveIndex();
+	int3 index = int3(indices[3 * PrimitiveID], indices[3 * PrimitiveID + 1], indices[3 * PrimitiveID + 2]);
+
+	Vertex v0 = unpack(index.x);
+	Vertex v1 = unpack(index.y);
+	Vertex v2 = unpack(index.z);
+
+	// Interpolate normal
+	const float3 barycentricCoords = float3(1.0f - attribs.x - attribs.y, attribs.x, attribs.y);
+	float3 normal = normalize(v0.normal * barycentricCoords.x + v1.normal * barycentricCoords.y + v2.normal * barycentricCoords.z);
+
+	// Basic lighting
+	float3 lightVector = normalize(ubo.lightPos.xyz);
+	float dot_product = max(dot(lightVector, normal), 0.2);
+	inPayload.hitValue = v0.color.rgb * dot_product;
+
+	RayDesc rayDesc;
+	rayDesc.Origin = WorldRayOrigin() + WorldRayDirection() * RayTCurrent();
+	rayDesc.Direction = lightVector;
+	rayDesc.TMin = 0.001;
+	rayDesc.TMax = 100.0;
+
+	inOutPayload.shadowed = true;
+	// Offset indices to match shadow hit/miss index
+	TraceRay(topLevelAS, RAY_FLAG_ACCEPT_FIRST_HIT_AND_END_SEARCH | RAY_FLAG_FORCE_OPAQUE | RAY_FLAG_SKIP_CLOSEST_HIT_SHADER, 0xff, 1, 0, 1, rayDesc, inOutPayload);
+	if (inOutPayload.shadowed) {
+		inPayload.hitValue *= 0.3;
+	}
+}

data/shaders/hlsl/raytracingshadows/miss.rmiss

@@ -0,0 +1,7 @@
+// Copyright 2020 Google LLC
+
+[shader("miss")]
+void main([[vk::location(0)]] in float3 hitValue)
+{
+    hitValue = float3(0.0, 0.0, 0.2);
+}

data/shaders/hlsl/raytracingshadows/raygen.rgen

@@ -0,0 +1,40 @@
+// Copyright 2020 Google LLC
+
+RaytracingAccelerationStructure rs : register(t0);
+RWTexture2D<float4> image : register(u1);
+
+struct CameraProperties
+{
+	float4x4 viewInverse;
+	float4x4 projInverse;
+	float4 lightPos;
+};
+cbuffer cam : register(b2) { CameraProperties cam; };
+
+struct Payload
+{
+	[[vk::location(0)]] float3 hitValue;
+};
+
+[shader("raygeneration")]
+void main()
+{
+	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(cam.projInverse, float4(d.x, d.y, 1, 1));
+
+	RayDesc rayDesc;
+	rayDesc.Origin = mul(cam.viewInverse, float4(0,0,0,1)).xyz;
+	rayDesc.Direction = mul(cam.viewInverse, float4(normalize(target.xyz), 0)).xyz;
+	rayDesc.TMin = 0.001;
+	rayDesc.TMax = 10000.0;
+
+	Payload payload;
+	TraceRay(rs, RAY_FLAG_FORCE_OPAQUE, 0xff, 0, 0, 0, rayDesc, payload);
+
+	image[int2(LaunchID.xy)] = float4(payload.hitValue, 0.0);
+}

data/shaders/hlsl/raytracingshadows/shadow.rmiss

@@ -0,0 +1,7 @@
+// Copyright 2020 Google LLC
+
+[shader("miss")]
+void main([[vk::location(2)]] in bool shadowed)
+{
+	shadowed = false;
+}