--- /dev/null
+// Author: Ilya Khramov
+// Copyright (c) 2019 OPEN CASCADE SAS
+//
+// This file is part of Open CASCADE Technology software library.
+//
+// This library is free software; you can redistribute it and/or modify it under
+// the terms of the GNU Lesser General Public License version 2.1 as published
+// by the Free Software Foundation, with special exception defined in the file
+// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
+// distribution for complete text of the license and disclaimer of any warranty.
+//
+// Alternatively, this file may be used under the terms of Open CASCADE
+// commercial license or contractual agreement.
+
+#ifndef _Graphic3d_PBRMaterial_HeaderFile
+#define _Graphic3d_PBRMaterial_HeaderFile
+
+#include <Image_PixMap.hxx>
+#include <Graphic3d_BSDF.hxx>
+#include <Graphic3d_Vec2.hxx>
+#include <Graphic3d_Vec3.hxx>
+#include <Graphic3d_Vec4.hxx>
+#include <Quantity_Color.hxx>
+
+//! Class implementing Metallic-Roughness physically based material definition
+class Graphic3d_PBRMaterial
+{
+public:
+
+ //! Creates new physically based material in Metallic-Roughness system.
+ //! 'metallic' parameter is 0 by default.
+ //! 'roughness' parameter is 1 by default.
+ //! 'color' parameter is (0, 0, 0) by default.
+ //! 'alpha' parameter is 1 by default.
+ //! 'IOR' parameter is 1.5 by default.
+ //! 'emission' parameter is (0, 0, 0) by default.
+ Standard_EXPORT Graphic3d_PBRMaterial();
+
+ //! Creates new physically based material in Metallic-Roughness system from Graphic3d_BSDF.
+ Standard_EXPORT Graphic3d_PBRMaterial (const Graphic3d_BSDF& theBSDF);
+
+ //! Returns material's metallic coefficient in [0, 1] range.
+ //! 1 for metals and 0 for dielectrics.
+ //! It is preferable to be exactly 0 or 1. Average values are needed for textures mixing in shader.
+ Standard_ShortReal Metallic() const { return myMetallic; }
+
+ //! Modifies metallic coefficient of material in [0, 1] range.
+ Standard_EXPORT void SetMetallic (Standard_ShortReal theMetallic);
+
+ //! Maps roughness from [0, 1] to [MinRoughness, 1] for calculations.
+ Standard_EXPORT static Standard_ShortReal Roughness(Standard_ShortReal theNormalizedRoughness);
+
+ //! Returns real value of roughness in [MinRoughness, 1] range for calculations.
+ Standard_ShortReal Roughness() const { return Roughness(myRoughness); }
+
+ //! Returns roughness mapping parameter in [0, 1] range.
+ //! Roughness is defined in [0, 1] for handful material settings
+ //! and is mapped to [MinRoughness, 1] for calculations.
+ Standard_ShortReal NormalizedRoughness() const { return myRoughness; }
+
+ //! Modifies roughness coefficient of material in [0, 1] range.
+ Standard_EXPORT void SetRoughness (Standard_ShortReal theRoughness);
+
+ //! Returns index of refraction in [1, 3] range.
+ Standard_ShortReal IOR() const { return myIOR; }
+
+ //! Modifies index of refraction in [1, 3] range.
+ //! In practice affects only on non-metal materials reflection possibilities.
+ Standard_EXPORT void SetIOR (Standard_ShortReal theIOR);
+
+ //! Returns albedo color with alpha component of material.
+ const Quantity_ColorRGBA& Color() const { return myColor; }
+
+ //! Modifies albedo color with alpha component.
+ Standard_EXPORT void SetColor (const Quantity_ColorRGBA& theColor);
+
+ //! Modifies only albedo color.
+ Standard_EXPORT void SetColor (const Quantity_Color& theColor);
+
+ //! Returns alpha component in range [0, 1].
+ Standard_ShortReal Alpha() const { return myColor.Alpha(); };
+
+ //! Modifies alpha component.
+ Standard_EXPORT void SetAlpha (Standard_ShortReal theAlpha);
+
+ //! Returns light intensity emitted by material.
+ //! Values are greater or equal 0.
+ Graphic3d_Vec3 Emission() const { return myEmission; }
+
+ //! Modifies light intensity emitted by material.
+ Standard_EXPORT void SetEmission (const Graphic3d_Vec3& theEmission);
+
+ //! Generates material in Metallic-Roughness system from Graphic3d_BSDF.
+ Standard_EXPORT void SetBSDF (const Graphic3d_BSDF& theBSDF);
+
+public:
+
+ //! PBR materials comparison operator.
+ Standard_Boolean operator== (const Graphic3d_PBRMaterial& theOther) const
+ {
+ return (myMetallic == theOther.myMetallic)
+ && (myRoughness == theOther.myRoughness)
+ && (myIOR == theOther.myIOR)
+ && (myColor == theOther.myColor)
+ && (myEmission == theOther.myEmission);
+ }
+
+public:
+
+ //! Generates 2D look up table of scale and bias for fresnell zero coefficient.
+ //! It is needed for calculation reflectance part of environment lighting.
+ //! @param [out] theLUT table storage (must be Image_Format_RGF).
+ //! @param [in] theIntegralSamplesCount number of importance samples in hemisphere integral calculation for every table item.
+ Standard_EXPORT static void GenerateEnvLUT (const Handle(Image_PixMap)& theLUT,
+ unsigned int theNbIntegralSamples = 1024);
+
+ //! Compute material roughness from common material (specular color + shininess).
+ //! @param theSpecular [in] specular color
+ //! @param theShiness [in] normalized shininess coefficient within [0..1] range
+ //! @return roughness within [0..1] range
+ Standard_EXPORT static Standard_ShortReal RoughnessFromSpecular (const Quantity_Color& theSpecular,
+ const Standard_Real theShiness);
+
+ //! Compute material metallicity from common material (specular color).
+ //! @param theSpecular [in] specular color
+ //! @return metallicity within [0..1] range
+ static Standard_ShortReal MetallicFromSpecular (const Quantity_Color& theSpecular)
+ {
+ return ((Graphic3d_Vec3 )theSpecular).maxComp();
+ }
+
+public:
+
+ //! Roughness cannot be 0 in real calculations, so it returns minimal achievable level of roughness in practice
+ static Standard_ShortReal MinRoughness() { return 0.01f; }
+
+public:
+
+ //! Shows how much times less samples can be used in certain roughness value specular IBL map generation
+ //! in compare with samples number for map with roughness of 1.
+ //! Specular IBL maps with less roughness values have higher resolution but require less samples for the same quality of baking.
+ //! So that reducing samples number is good strategy to improve performance of baking.
+ //! The samples number for specular IBL map with roughness of 1 (the maximum possible samples number) is expected to be defined as baking parameter.
+ //! Samples number for other roughness values can be calculated by multiplication origin samples number by this factor.
+ //! @param theProbability value from 0 to 1 controlling strength of samples reducing.
+ //! Bigger values result in slower reduction to provide better quality but worse performance.
+ //! Value of 1 doesn't affect at all so that 1 will be returned (it can be used to disable reduction strategy).
+ //! @param theRoughness roughness value of current generated specular IBL map (from 0 to 1).
+ //! @return factor to calculate number of samples for current specular IBL map baking.
+ //! Be aware! It has no obligation to return 1 in case of roughness of 1.
+ //! Be aware! It produces poor quality with small number of origin samples. In that case it is recommended to be disabled.
+ Standard_EXPORT static Standard_ShortReal SpecIBLMapSamplesFactor (Standard_ShortReal theProbability,
+ Standard_ShortReal theRoughness);
+
+private:
+
+ //! Calculates geometry factor of Cook-Torrance BRDF using Smith formula.
+ static Standard_ShortReal lutGenGeometryFactor (Standard_ShortReal theCosL,
+ Standard_ShortReal theCosV,
+ Standard_ShortReal theRoughness);
+
+ //! Generates quasi-random point from Hammersley set.
+ //! @param theNumber number of point
+ //! @param theCount size of Hammersley set
+ static Graphic3d_Vec2 lutGenHammersley (unsigned int theNumber, unsigned int theCount);
+
+ //! Generates only cosine theta of direction in spherical coordinates system
+ //! according to micro facet distribution function from Cook-Torrance BRDF.
+ static Standard_ShortReal lutGenImportanceSampleCosTheta (Standard_ShortReal theHammerslayPointComponent,
+ Standard_ShortReal theRoughness);
+
+ //! Generates direction using point from Hammersley set
+ //! according to micro facet distribution function from Cook-Torrance BRDF.
+ static Graphic3d_Vec3 lutGenImportanceSample (const Graphic3d_Vec2 &theHammerslayPoint,
+ Standard_ShortReal theRoughness);
+
+ //! Generates vector using cosine of angle between up vector (normal in hemisphere)
+ //! and desired vector.
+ //! x component for resulting vector will be zero.
+ static Graphic3d_Vec3 lutGenView (Standard_ShortReal theCosV);
+
+ //! Returns reflected vector according axis.
+ //! @param theVector vector is needed to be reflected.
+ //! @param theAxis axis of reflection.
+ static Graphic3d_Vec3 lutGenReflect (const Graphic3d_Vec3 &theVector,
+ const Graphic3d_Vec3 &theAxis);
+
+private:
+
+ Quantity_ColorRGBA myColor; //!< albedo color with alpha component [0, 1]
+ Standard_ShortReal myMetallic; //!< metallic coefficient of material [0, 1]
+ Standard_ShortReal myRoughness; //!< roughness coefficient of material [0, 1]
+ Graphic3d_Vec3 myEmission; //!< light intensity emitted by material [>= 0]
+ Standard_ShortReal myIOR; //!< index of refraction [1, 3]
+
+};
+
+#endif // _Graphic3d_PBRMaterial_HeaderFile