ScriptableRenderPipeline/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.cs

using UnityEngine.Rendering;

namespace UnityEngine.Experimental.Rendering.HDPipeline
{
    public partial class Lit : RenderPipelineMaterial
    {
        [GenerateHLSL(PackingRules.Exact)]
        public enum MaterialId
        {
            LitSSS          = 0,
            LitStandard     = 1,
            LitAniso        = 2,
            LitClearCoat    = 3,
            // LitSpecular (DiffuseColor/SpecularColor) is an alternate parametrization for LitStandard (BaseColor/Metal/Specular), but it is the same shading model
            // We don't want any specific materialId for it, instead we use LitStandard as materialId. However for UI purpose we still define this value here.
            // For material classification we will use LitStandard too
            LitSpecular     = 4,
        };

        // If change, be sure it match what is done in Lit.hlsl: MaterialFeatureFlagsFromGBuffer
        // Material bit mask must match LightDefinitions.s_MaterialFeatureMaskFlags value
        [GenerateHLSL]
        public enum MaterialFeatureFlags
        {
            LitSSS          = 1 << MaterialId.LitSSS,
            LitStandard     = 1 << MaterialId.LitStandard,
            LitAniso        = 1 << MaterialId.LitAniso,
            LitClearCoat    = 1 << MaterialId.LitClearCoat,
        };

        [GenerateHLSL]
        public class StandardDefinitions
        {
            public static int s_GBufferLitStandardRegularId = 0;
            public static int s_GBufferLitStandardSpecularColorId = 1;

            public static float s_DefaultSpecularValue = 0.04f;
            public static float s_SkinSpecularValue = 0.028f;
        }

        [GenerateHLSL(PackingRules.Exact)]
        public enum RefractionMode
        {
            None = 0,
            ThickPlane = 1,
            ThickSphere = 2,
            ThinPlane = 3
        };

        //-----------------------------------------------------------------------------
        // SurfaceData
        //-----------------------------------------------------------------------------

        // Main structure that store the user data (i.e user input of master node in material graph)
        [GenerateHLSL(PackingRules.Exact, false, true, 1000)]
        public struct SurfaceData
        {
            [SurfaceDataAttributes("Base Color", false, true)]
            public Vector3 baseColor;
            [SurfaceDataAttributes("Specular Occlusion")]
            public float specularOcclusion;

            [SurfaceDataAttributes("Normal", true)]
            public Vector3 normalWS;
            [SurfaceDataAttributes("Smoothness")]
            public float perceptualSmoothness;
            [SurfaceDataAttributes("Material ID")]
            public MaterialId materialId; // matId above 3 are store in standard material gbuffer (2bit reserved)

            [SurfaceDataAttributes("Ambient Occlusion")]
            public float ambientOcclusion;

            // MaterialId dependent attribute

            // standard
            [SurfaceDataAttributes("Tangent", true)]
            public Vector3 tangentWS;
            [SurfaceDataAttributes("Anisotropy")]
            public float anisotropy; // anisotropic ratio(0->no isotropic; 1->full anisotropy in tangent direction)
            [SurfaceDataAttributes("Metallic")]
            public float metallic;

            // SSS
            [SurfaceDataAttributes("Subsurface Radius")]
            public float subsurfaceRadius;
            [SurfaceDataAttributes("Thickness")]
            public float thickness;
            [SurfaceDataAttributes("Subsurface Profile")]
            public int subsurfaceProfile;

            // SpecColor
            [SurfaceDataAttributes("Specular Color", false, true)]
            public Vector3 specularColor;

            // ClearCoat
            [SurfaceDataAttributes("Coat Normal", true)]
            public Vector3 coatNormalWS;
            [SurfaceDataAttributes("Coat coverage")]
            public float coatCoverage;
            [SurfaceDataAttributes("Coat IOR")]
            public float coatIOR; // Value is [0..1] for artists but the UI will display the value between [1..2]

            // Transparency
            [SurfaceDataAttributes("Indice of refraction")]
            public float ior;
            // Reuse thickness from SSS
            [SurfaceDataAttributes("Transmittance Color")]
            public Vector3 transmittanceColor;
            [SurfaceDataAttributes("Transmittance Absorption Distance")]
            public float atDistance;
        };

        //-----------------------------------------------------------------------------
        // BSDFData
        //-----------------------------------------------------------------------------

        [GenerateHLSL(PackingRules.Exact)]
        public enum TransmissionType
        {
            None = 0,
            Regular = 1,
            ThinObject = 2,
        };

        [GenerateHLSL(PackingRules.Exact, false, true, 1030)]
        public struct BSDFData
        {
            [SurfaceDataAttributes("", false, true)]
            public Vector3 diffuseColor;

            public Vector3 fresnel0;

            public float specularOcclusion;

            [SurfaceDataAttributes("", true)]
            public Vector3 normalWS;
            public float perceptualRoughness;
            public float roughness;
            public int materialId;

            // MaterialId dependent attribute

            // standard
            [SurfaceDataAttributes("", true)]
            public Vector3 tangentWS;
            [SurfaceDataAttributes("", true)]
            public Vector3 bitangentWS;
            public float roughnessT;
            public float roughnessB;
            public float anisotropy;

            // fold into fresnel0

            // SSS
            public float   subsurfaceRadius;
            public float   thickness;
            public int     subsurfaceProfile;
            public bool    enableTransmission; // Read from the SSS profile
            public bool    useThinObjectMode;  // Read from the SSS profile
            public Vector3 transmittance;

            // SpecColor
            // fold into fresnel0

            // ClearCoat
            public Vector3 coatNormalWS;
            public float coatCoverage;
            public float coatIOR; // CoatIOR is in range[1..2] it is surfaceData + 1

            // Transparency
            public float ior;
            // Reuse thickness from SSS
            public Vector3 absorptionCoefficient;
        };

        //-----------------------------------------------------------------------------
        // RenderLoop management
        //-----------------------------------------------------------------------------

        [GenerateHLSL(PackingRules.Exact)]
        public enum GBufferMaterial
        {
            // Note: This count doesn't include the velocity buffer. On shader and csharp side the velocity buffer will be added by the framework
            Count = (ShaderConfig.k_PackgbufferInU16 == 1) ? 2 : 4
        };

        //-----------------------------------------------------------------------------
        // GBuffer management
        //-----------------------------------------------------------------------------

        public override int GetMaterialGBufferCount() { return (int)GBufferMaterial.Count; }

        public override void GetMaterialGBufferDescription(out RenderTextureFormat[] RTFormat, out RenderTextureReadWrite[] RTReadWrite)
        {
            RTFormat = new RenderTextureFormat[(int)GBufferMaterial.Count];
            RTReadWrite = new RenderTextureReadWrite[(int)GBufferMaterial.Count];

            if (ShaderConfig.s_PackgbufferInU16 == 1)
            {
                // TODO: Just discovered that Unity doesn't support unsigned 16 RT format.
                RTFormat[0] = RenderTextureFormat.ARGBInt; RTReadWrite[0] = RenderTextureReadWrite.Linear;
                RTFormat[1] = RenderTextureFormat.ARGBInt; RTReadWrite[1] = RenderTextureReadWrite.Linear;
            }
            else
            {
                RTFormat[0] = RenderTextureFormat.ARGB32; RTReadWrite[0] = RenderTextureReadWrite.sRGB;
                RTFormat[1] = RenderTextureFormat.ARGB2101010; RTReadWrite[1] = RenderTextureReadWrite.Linear;
                RTFormat[2] = RenderTextureFormat.ARGB32; RTReadWrite[2] = RenderTextureReadWrite.Linear;
                RTFormat[3] = RenderTextureFormat.RGB111110Float; RTReadWrite[3] = RenderTextureReadWrite.Linear;
            }
        }

        //-----------------------------------------------------------------------------
        // Init precomputed texture
        //-----------------------------------------------------------------------------

        bool m_isInit;

        // For image based lighting
        Material      m_InitPreFGD;
        RenderTexture m_PreIntegratedFGD;

        // For area lighting - We pack all texture inside a texture array to reduce the number of resource required
        Texture2DArray m_LtcData; // 0: m_LtcGGXMatrix - RGBA, 2: m_LtcDisneyDiffuseMatrix - RGBA, 3: m_LtcMultiGGXFresnelDisneyDiffuse - RGB, A unused

        const int k_LtcLUTMatrixDim  =  3; // size of the matrix (3x3)
        const int k_LtcLUTResolution = 64;


        // Load LUT with one scalar in alpha of a tex2D
        void LoadLUT(Texture2DArray tex, int arrayElement, TextureFormat format, float[] LUTScalar)
        {
            const int count = k_LtcLUTResolution * k_LtcLUTResolution;
            Color[] pixels = new Color[count];

            for (int i = 0; i < count; i++)
            {
                pixels[i] = new Color(0, 0, 0, LUTScalar[i]);
            }

            tex.SetPixels(pixels, arrayElement);
        }

        // Load LUT with 3x3 matrix in RGBA of a tex2D (some part are zero)
        void LoadLUT(Texture2DArray tex, int arrayElement, TextureFormat format, double[,] LUTTransformInv)
        {
            const int count = k_LtcLUTResolution * k_LtcLUTResolution;
            Color[] pixels = new Color[count];

            for (int i = 0; i < count; i++)
            {
                // Both GGX and Disney Diffuse BRDFs have zero values in columns 1, 3, 5, 7.
                // Column 8 contains only ones.
                pixels[i] = new Color((float)LUTTransformInv[i, 0],
                        (float)LUTTransformInv[i, 2],
                        (float)LUTTransformInv[i, 4],
                        (float)LUTTransformInv[i, 6]);
            }

            tex.SetPixels(pixels, arrayElement);
        }

        // Special-case function for 'm_LtcMultiGGXFresnelDisneyDiffuse'.
        void LoadLUT(Texture2DArray tex, int arrayElement, TextureFormat format,   float[] LtcGGXMagnitudeData,
            float[] LtcGGXFresnelData,
            float[] LtcDisneyDiffuseMagnitudeData)
        {
            const int count = k_LtcLUTResolution * k_LtcLUTResolution;
            Color[] pixels = new Color[count];

            for (int i = 0; i < count; i++)
            {
                // We store the result of the subtraction as a run-time optimization.
                // See the footnote 2 of "LTC Fresnel Approximation" by Stephen Hill.
                pixels[i] = new Color(LtcGGXMagnitudeData[i] - LtcGGXFresnelData[i],
                        LtcGGXFresnelData[i], LtcDisneyDiffuseMagnitudeData[i], 1);
            }

            tex.SetPixels(pixels, arrayElement);
        }

        public Lit() {}

        public override void Build(RenderPipelineResources renderPipelineResources)
        {
            m_InitPreFGD = CoreUtils.CreateEngineMaterial("Hidden/HDRenderPipeline/PreIntegratedFGD");

            // For DisneyDiffuse integration values goes from (0.5 to 1.53125). GGX need 0 to 1. Use float format.
            m_PreIntegratedFGD = new RenderTexture(128, 128, 0, RenderTextureFormat.RGB111110Float, RenderTextureReadWrite.Linear);
            m_PreIntegratedFGD.filterMode = FilterMode.Bilinear;
            m_PreIntegratedFGD.wrapMode = TextureWrapMode.Clamp;
            m_PreIntegratedFGD.hideFlags = HideFlags.DontSave;
            m_PreIntegratedFGD.Create();

            m_LtcData = new Texture2DArray(k_LtcLUTResolution, k_LtcLUTResolution, 3, TextureFormat.RGBAHalf, false /*mipmap*/, true /* linear */)
            {
                hideFlags = HideFlags.HideAndDontSave,
                wrapMode = TextureWrapMode.Clamp,
                filterMode = FilterMode.Bilinear
            };

            LoadLUT(m_LtcData, 0, TextureFormat.RGBAHalf,   s_LtcGGXMatrixData);
            LoadLUT(m_LtcData, 1, TextureFormat.RGBAHalf,   s_LtcDisneyDiffuseMatrixData);
            // TODO: switch to RGBA64 when it becomes available.
            LoadLUT(m_LtcData, 2, TextureFormat.RGBAHalf,   s_LtcGGXMagnitudeData, s_LtcGGXFresnelData, s_LtcDisneyDiffuseMagnitudeData);

            m_LtcData.Apply();

            m_isInit = false;
        }

        public override void Cleanup()
        {
            CoreUtils.Destroy(m_InitPreFGD);

            // TODO: how to delete RenderTexture ? or do we need to do it ?
            m_isInit = false;
        }

        public override void RenderInit(CommandBuffer cmd)
        {
            if (m_isInit)
                return;

            using (new ProfilingSample(cmd, "Init PreFGD"))
            {
                CoreUtils.DrawFullScreen(cmd, m_InitPreFGD, new RenderTargetIdentifier(m_PreIntegratedFGD));
            }
            m_isInit = true;
        }

        public override void Bind()
        {
            Shader.SetGlobalTexture("_PreIntegratedFGD", m_PreIntegratedFGD);
            Shader.SetGlobalTexture("_LtcData", m_LtcData);
        }
    }
}