Refactor material shaders generator to use modular features as extensions

Content/Editor/MaterialTemplates/Features/Lightmap.hlsl

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+// Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
+
+@0// Lightmap: Defines
+@1// Lightmap: Includes
+@2// Lightmap: Constants
+float4 LightmapArea;
+@3// Lightmap: Resources
+#if USE_LIGHTMAP
+// Irradiance and directionality prebaked lightmaps
+Texture2D Lightmap0 : register(t__SRV__);
+Texture2D Lightmap1 : register(t__SRV__);
+Texture2D Lightmap2 : register(t__SRV__);
+#endif
+@4// Lightmap: Utilities
+#if USE_LIGHTMAP
+
+// Evaluates the H-Basis coefficients in the tangent space normal direction
+float3 GetHBasisIrradiance(float3 n, float3 h0, float3 h1, float3 h2, float3 h3)
+{
+	// Band 0
+	float3 color = h0 * (1.0f / sqrt(2.0f * PI));
+
+	// Band 1
+	color += h1 * -sqrt(1.5f / PI) * n.y;
+	color += h2 *  sqrt(1.5f / PI) * (2 * n.z - 1.0f);
+	color += h3 * -sqrt(1.5f / PI) * n.x;
+
+	return color;
+}
+
+float3 SampleLightmap(Material material, MaterialInput materialInput)
+{
+	// Sample lightmaps
+	float4 lightmap0 = Lightmap0.Sample(SamplerLinearClamp, materialInput.LightmapUV);
+	float4 lightmap1 = Lightmap1.Sample(SamplerLinearClamp, materialInput.LightmapUV);
+	float4 lightmap2 = Lightmap2.Sample(SamplerLinearClamp, materialInput.LightmapUV);
+
+	// Unpack H-basis
+	float3 h0 = float3(lightmap0.x, lightmap1.x, lightmap2.x);
+	float3 h1 = float3(lightmap0.y, lightmap1.y, lightmap2.y);
+	float3 h2 = float3(lightmap0.z, lightmap1.z, lightmap2.z);
+	float3 h3 = float3(lightmap0.w, lightmap1.w, lightmap2.w);
+
+	// Sample baked diffuse irradiance from the H-basis coefficients
+	float3 normal = material.TangentNormal;
+#if MATERIAL_SHADING_MODEL == SHADING_MODEL_FOLIAGE
+	normal *= material.TangentNormal;
+#endif
+	return GetHBasisIrradiance(normal, h0, h1, h2, h3) / PI;
+}
+
+#endif
+@5// Lightmap: Shaders