Add shaders re-implemented in HLSL

These were written against the shaders at revision eddd724e7.
There have been changes made since then, which will need to be mirrored.

See `data/hlsl/README.md` for the current status of each sample.

data/hlsl/deferredshadows/deferred.frag

@@ -0,0 +1,146 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureposition : register(t1);
+SamplerState samplerposition : register(s1);
+Texture2D textureNormal : register(t2);
+SamplerState samplerNormal : register(s2);
+Texture2D textureAlbedo : register(t3);
+SamplerState samplerAlbedo : register(s3);
+// Depth from the light's point of view
+//layout (binding = 5) uniform sampler2DShadow samplerShadowMap;
+Texture2DArray textureShadowMap : register(t5);
+SamplerState samplerShadowMap : register(s5);
+
+#define LIGHT_COUNT 3
+#define SHADOW_FACTOR 0.25
+#define AMBIENT_LIGHT 0.1
+#define USE_PCF
+
+struct Light
+{
+	float4 position;
+	float4 target;
+	float4 color;
+	float4x4 viewMatrix;
+};
+
+struct UBO
+{
+	float4 viewPos;
+	Light lights[LIGHT_COUNT];
+	int useShadows;
+};
+
+cbuffer ubo : register(b4) { UBO ubo; }
+
+float textureProj(float4 P, float layer, float2 offset)
+{
+	float shadow = 1.0;
+	float4 shadowCoord = P / P.w;
+	shadowCoord.xy = shadowCoord.xy * 0.5 + 0.5;
+
+	if (shadowCoord.z > -1.0 && shadowCoord.z < 1.0)
+	{
+		float dist = textureShadowMap.Sample(samplerShadowMap, float3(shadowCoord.xy + offset, layer)).r;
+		if (shadowCoord.w > 0.0 && dist < shadowCoord.z)
+		{
+			shadow = SHADOW_FACTOR;
+		}
+	}
+	return shadow;
+}
+
+float filterPCF(float4 sc, float layer)
+{
+	int2 texDim; int elements; int levels;
+	textureShadowMap.GetDimensions(0, texDim.x, texDim.y, elements, levels);
+	float scale = 1.5;
+	float dx = scale * 1.0 / float(texDim.x);
+	float dy = scale * 1.0 / float(texDim.y);
+
+	float shadowFactor = 0.0;
+	int count = 0;
+	int range = 1;
+
+	for (int x = -range; x <= range; x++)
+	{
+		for (int y = -range; y <= range; y++)
+		{
+			shadowFactor += textureProj(sc, layer, float2(dx*x, dy*y));
+			count++;
+		}
+
+	}
+	return shadowFactor / count;
+}
+
+float4 main([[vk::location(0)]] float2 inUV : TEXCOORD0) : SV_TARGET
+{
+	// Get G-Buffer values
+	float3 fragPos = textureposition.Sample(samplerposition, inUV).rgb;
+	float3 normal = textureNormal.Sample(samplerNormal, inUV).rgb;
+	float4 albedo = textureAlbedo.Sample(samplerAlbedo, inUV);
+
+	// Ambient part
+	float3 fragcolor  = albedo.rgb * AMBIENT_LIGHT;
+
+	float3 N = normalize(normal);
+
+	float shadow = 0.0;
+
+	for(int i = 0; i < LIGHT_COUNT; ++i)
+	{
+		// Vector to light
+		float3 L = ubo.lights[i].position.xyz - fragPos;
+		// Distance from light to fragment position
+		float dist = length(L);
+		L = normalize(L);
+
+		// Viewer to fragment
+		float3 V = ubo.viewPos.xyz - fragPos;
+		V = normalize(V);
+
+		float lightCosInnerAngle = cos(radians(15.0));
+		float lightCosOuterAngle = cos(radians(25.0));
+		float lightRange = 100.0;
+
+		// Direction vector from source to target
+		float3 dir = normalize(ubo.lights[i].position.xyz - ubo.lights[i].target.xyz);
+
+		// Dual cone spot light with smooth transition between inner and outer angle
+		float cosDir = dot(L, dir);
+		float spotEffect = smoothstep(lightCosOuterAngle, lightCosInnerAngle, cosDir);
+		float heightAttenuation = smoothstep(lightRange, 0.0f, dist);
+
+		// Diffuse lighting
+		float NdotL = max(0.0, dot(N, L));
+		float3 diff = NdotL.xxx;
+
+		// Specular lighting
+		float3 R = reflect(-L, N);
+		float NdotR = max(0.0, dot(R, V));
+		float3 spec = (pow(NdotR, 16.0) * albedo.a * 2.5).xxx;
+
+		fragcolor += float3((diff + spec) * spotEffect * heightAttenuation) * ubo.lights[i].color.rgb * albedo.rgb;
+	}
+
+	// Shadow calculations in a separate pass
+	if (ubo.useShadows > 0)
+	{
+		for(int i = 0; i < LIGHT_COUNT; ++i)
+		{
+			float4 shadowClip	= mul(ubo.lights[i].viewMatrix, float4(fragPos, 1.0));
+
+			float shadowFactor;
+			#ifdef USE_PCF
+				shadowFactor= filterPCF(shadowClip, i);
+			#else
+				shadowFactor = textureProj(shadowClip, i, float2(0.0, 0.0));
+			#endif
+
+			fragcolor *= shadowFactor;
+		}
+	}
+
+	return float4(fragcolor, 1);
+}