0031096: Visualization, TKOpenGl - support metallic-roughness texture mapping

OpenGl_ShaderManager - metallic-roughness, emissive, occlusion
and normal texture maps are now supported by PBR.
Emissive, occlusion and normal texture maps are now supported by Phong shading model.
Path-Tracing now handles metallic-roughness and emissive texture maps.

Graphic3d_TextureUnit enumeration has been extended by
new values corresponding to supported texture maps.

OpenGl_TextureSet and OpenGl_ShaderProgram have been extended with
bitmask Graphic3d_TextureSetBits identifying texture slots read from GLSL Program
and slots defined within Texture Set to avoid undefined behavior by binding mock textures.

OpenGl_TextureSet now duplicates texture unit information to handle
textures shared across multiple slots (like Occlusion [R] + Metallic-Roughness [GB]).

OpenGl_Context::BindTextures() has been extended with active GLSL program paramter
to set mock textures to texture units used by program but undefined by texture set.
OpenGl_Workspace::ApplyAspects() has been extended with parameter to avoid bining texture set.

src/Graphic3d/FILES

@@ -164,6 +164,7 @@ Graphic3d_TextureRoot.hxx
 Graphic3d_TextureUnit.hxx
 Graphic3d_TextureSet.cxx
 Graphic3d_TextureSet.hxx
+Graphic3d_TextureSetBits.hxx
 Graphic3d_ToneMappingMethod.hxx
 Graphic3d_TransformError.hxx
 Graphic3d_TransformPers.hxx

src/Graphic3d/Graphic3d_BSDF.cxx

@@ -208,5 +208,6 @@ Graphic3d_BSDF Graphic3d_BSDF::CreateMetallicRoughness (const Graphic3d_PBRMater
   aBsdf.Ks.SetValues (Graphic3d_Vec3 (thePbr.Alpha()), aRougness2);
   aBsdf.Kt = Graphic3d_Vec3 (1.0f - thePbr.Alpha());
   aBsdf.Kd = aDiff * (1.0f - thePbr.Metallic());
+  aBsdf.Le = thePbr.Emission();
   return aBsdf;
 }

src/Graphic3d/Graphic3d_ShaderProgram.cxx

@@ -80,6 +80,7 @@ Graphic3d_ShaderProgram::Graphic3d_ShaderProgram()
 : myNbLightsMax (THE_MAX_LIGHTS_DEFAULT),
   myNbClipPlanesMax (THE_MAX_CLIP_PLANES_DEFAULT),
   myNbFragOutputs (THE_NB_FRAG_OUTPUTS),
+  myTextureSetBits (Graphic3d_TextureSetBits_NONE),
   myHasDefSampler (true),
   myHasAlphaTest (false),
   myHasWeightOitOutput (false),

src/Graphic3d/Graphic3d_ShaderProgram.hxx

@@ -20,6 +20,7 @@
 #include <Graphic3d_ShaderObject.hxx>
 #include <Graphic3d_ShaderVariable.hxx>
 #include <Graphic3d_TextureParams.hxx>
+#include <Graphic3d_TextureSetBits.hxx>
 #include <NCollection_Sequence.hxx>
 
 //! List of shader objects.
@@ -152,12 +153,18 @@ public:
   void SetWeightOitOutput (Standard_Boolean theOutput) { myHasWeightOitOutput = theOutput; }
 
   //! Return TRUE if standard program header should define functions and variables used in PBR pipeline.
-  //! FALSE by default
+  //! FALSE by default.
   Standard_Boolean IsPBR() const { return myIsPBR; }
 
   //! Sets whether standard program header should define functions and variables used in PBR pipeline.
   void SetPBR (Standard_Boolean theIsPBR) { myIsPBR = theIsPBR; }
 
+  //! Return texture units declared within the program, @sa Graphic3d_TextureSetBits.
+  Standard_Integer TextureSetBits() const { return myTextureSetBits; }
+
+  //! Set texture units declared within the program.
+  void SetTextureSetBits (Standard_Integer theBits) { myTextureSetBits = theBits; }
+
   //! Pushes custom uniform variable to the program.
   //! The list of pushed variables is automatically cleared after applying to GLSL program.
   //! Thus after program recreation even unchanged uniforms should be pushed anew.
@@ -208,6 +215,7 @@ private:
   Standard_Integer              myNbLightsMax;   //!< length of array of light sources (THE_MAX_LIGHTS)
   Standard_Integer              myNbClipPlanesMax; //!< length of array of clipping planes (THE_MAX_CLIP_PLANES)
   Standard_Integer              myNbFragOutputs; //!< length of array of Fragment Shader outputs (THE_NB_FRAG_OUTPUTS)
+  Standard_Integer              myTextureSetBits;//!< texture units declared within the program, @sa Graphic3d_TextureSetBits
   Standard_Boolean              myHasDefSampler; //!< flag indicating that program defines default texture sampler occSampler0
   Standard_Boolean              myHasAlphaTest;       //!< flag indicating that Fragment Shader performs alpha test
   Standard_Boolean              myHasWeightOitOutput; //!< flag indicating that Fragment Shader includes weighted OIT coverage

src/Graphic3d/Graphic3d_TextureSetBits.hxx

@@ -0,0 +1,30 @@
+// 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_TextureSetBits_HeaderFile
+#define _Graphic3d_TextureSetBits_HeaderFile
+
+#include <Graphic3d_TextureUnit.hxx>
+
+//! Standard texture units combination bits.
+enum Graphic3d_TextureSetBits
+{
+  Graphic3d_TextureSetBits_NONE              = 0,
+  Graphic3d_TextureSetBits_BaseColor         = (unsigned int )(1 << int(Graphic3d_TextureUnit_BaseColor)),
+  Graphic3d_TextureSetBits_Emissive          = (unsigned int )(1 << int(Graphic3d_TextureUnit_Emissive)),
+  Graphic3d_TextureSetBits_Occlusion         = (unsigned int )(1 << int(Graphic3d_TextureUnit_Occlusion)),
+  Graphic3d_TextureSetBits_Normal            = (unsigned int )(1 << int(Graphic3d_TextureUnit_Normal)),
+  Graphic3d_TextureSetBits_MetallicRoughness = (unsigned int )(1 << int(Graphic3d_TextureUnit_MetallicRoughness)),
+};
+
+#endif // _Graphic3d_TextureSetBits_HeaderFile

src/Graphic3d/Graphic3d_TextureUnit.hxx

@@ -35,17 +35,54 @@ enum Graphic3d_TextureUnit
   Graphic3d_TextureUnit_14,
   Graphic3d_TextureUnit_15,
 
-  Graphic3d_TextureUnit_BaseColor         = Graphic3d_TextureUnit_0, //!< base color of the material
-  //Graphic3d_TextureUnit_Normal            = Graphic3d_TextureUnit_1, //!< tangent space normal map
-  //Graphic3d_TextureUnit_MetallicRoughness = Graphic3d_TextureUnit_2, //!< metalness+roughness of the material
-  //Graphic3d_TextureUnit_Emissive          = Graphic3d_TextureUnit_3, //!< emissive map controls the color and intensity of the light being emitted by the material
-  //Graphic3d_TextureUnit_Occlusion         = Graphic3d_TextureUnit_4, //!< occlusion map indicating areas of indirect lighting
+  // aliases
 
-  Graphic3d_TextureUnit_EnvMap = Graphic3d_TextureUnit_0  //!< environment cubemap for background
+  //! sampler2D occSamplerBaseColor.
+  //! RGB(A) base color of the material and alpha mask/opacity.
+  Graphic3d_TextureUnit_BaseColor = Graphic3d_TextureUnit_0,
+  //! sampler2D occSamplerEmissive.
+  //! RGB emissive map controls the color and intensity of the light being emitted by the material.
+  Graphic3d_TextureUnit_Emissive  = Graphic3d_TextureUnit_1,
+  //! sampler2D occSamplerOcclusion.
+  //! Occlusion map indicating areas of indirect lighting.
+  //! Encoded into RED channel, with 1.0 meaning no occlusion (full color intensity) and 0.0 complete occlusion (black).
+  Graphic3d_TextureUnit_Occlusion = Graphic3d_TextureUnit_2,
+  //! sampler2D occSamplerNormal.
+  //! XYZ tangent space normal map.
+  Graphic3d_TextureUnit_Normal    = Graphic3d_TextureUnit_3,
+  //! sampler2D occSamplerMetallicRoughness.
+  //! Metalness + roughness of the material.
+  //! Encoded into GREEN (roughness) + BLUE (metallic) channels,
+  //! so that it can be optionally combined with occlusion texture (RED channel).
+  Graphic3d_TextureUnit_MetallicRoughness = Graphic3d_TextureUnit_4,
+
+  //! samplerCube occSampler0.
+  //! Environment cubemap for background. Rendered by dedicated program and normally occupies first texture unit.
+  Graphic3d_TextureUnit_EnvMap = Graphic3d_TextureUnit_0,
+
+  //! sampler2D occSamplerPointSprite.
+  //! Sprite alpha-mask or RGBA image mapped using point UV, additional to BaseColor (mapping using vertex UV).
+  //! This texture unit is set Graphic3d_TextureUnit_1, so that it can be combined with Graphic3d_TextureUnit_BaseColor,
+  //! while other texture maps (normal map and others) are unexpected and unsupported for points.
+  //! Note that it can be overridden to Graphic3d_TextureUnit_0 for FFP fallback on hardware without multi-texturing.
+  Graphic3d_TextureUnit_PointSprite = Graphic3d_TextureUnit_1,
+
+  //! sampler2D occEnvLUT.
+  //! Lookup table for approximated PBR environment lighting.
+  //! Configured as index at the end of available texture units - 3.
+  Graphic3d_TextureUnit_PbrEnvironmentLUT = -3,
+  //! sampler2D occDiffIBLMapSHCoeffs.
+  //! Diffuse (irradiance) IBL map's spherical harmonics coefficients baked for PBR from environment cubemap image.
+  //! Configured as index at the end of available texture units - 2.
+  Graphic3d_TextureUnit_PbrIblDiffuseSH   = -2,
+  //! samplerCube occSpecIBLMap.
+  //! Specular IBL (Image-Based Lighting) environment map baked for PBR from environment cubemap image.
+  //! Configured as index at the end of available texture units - 1.
+  Graphic3d_TextureUnit_PbrIblSpecular    = -1,
 };
 enum
 {
-  Graphic3d_TextureUnit_NB = Graphic3d_TextureUnit_15 + 1
+  Graphic3d_TextureUnit_NB = Graphic3d_TextureUnit_15 + 1,
 };
 
 #endif // _Graphic3d_TextureUnit_HeaderFile