// 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.

#include <OpenGl_PBREnvironment.hxx>

#include <Graphic3d_PBRMaterial.hxx>
#include <OpenGl_ArbFBO.hxx>
#include <OpenGl_FrameBuffer.hxx>
#include <OpenGl_ShaderManager.hxx>
#include <OpenGl_ShaderProgram.hxx>
#include <OSD_Timer.hxx>
#include <Message.hxx>
#include <Message_Messenger.hxx>

#include <algorithm>

IMPLEMENT_STANDARD_RTTIEXT(OpenGl_PBREnvironment, OpenGl_NamedResource)

//! Constructor of this class saves necessary OpenGL states components which can be changed by OpenGl_PBREnvironment.
//! Destructor restores state back.
class OpenGl_PBREnvironmentSentry
{
public:

  OpenGl_PBREnvironmentSentry (const Handle(OpenGl_Context)& theCtx)
  : myContext (theCtx)
  {
    backup();
    prepare();
  }

  ~OpenGl_PBREnvironmentSentry()
  {
    restore();
  }

private:

  void backup()
  {
    myColorMask = myContext->ColorMaskRGBA();
    myContext->core11fwd->glGetIntegerv (GL_FRAMEBUFFER_BINDING, &myFBO);
    myShaderProgram = myContext->ActiveProgram();
    for (unsigned int i = 0; i < 4; ++i)
    {
      myViewport[i] = myContext->Viewport()[i];
    }
    myContext->core11fwd->glGetFloatv (GL_COLOR_CLEAR_VALUE, myClearColor);

    GLboolean aStatus = GL_TRUE;
    myContext->core11fwd->glGetBooleanv (GL_DEPTH_TEST, &aStatus);
    myDepthTestWasEnabled = aStatus ? Standard_True : Standard_False;
    myContext->core11fwd->glGetBooleanv (GL_DEPTH_WRITEMASK, &aStatus);
    myDepthWrirtingWasEnablig = aStatus ? Standard_True : Standard_False;
    myContext->core11fwd->glGetBooleanv (GL_SCISSOR_TEST, &aStatus);
    myScissorTestWasEnabled = aStatus ? Standard_True : Standard_False;
    myContext->core11fwd->glGetIntegerv (GL_SCISSOR_BOX, myScissorBox);
  }

  void prepare()
  {
    myContext->BindDefaultVao();
    myContext->core11fwd->glDisable (GL_DEPTH_TEST);
    myContext->core11fwd->glDepthMask (GL_FALSE);
    myContext->core11fwd->glDisable (GL_BLEND);
    myContext->core11fwd->glDisable (GL_SCISSOR_TEST);
    myContext->SetColorMaskRGBA (NCollection_Vec4<bool> (true)); // force writes into all components, including alpha
  }

  void restore()
  {
    myContext->SetColorMaskRGBA (myColorMask);
    myContext->arbFBO->glBindFramebuffer (GL_FRAMEBUFFER, myFBO);
    myContext->BindProgram (myShaderProgram);
    myContext->ResizeViewport (myViewport);
    myContext->core11fwd->glClearColor (myClearColor.r(), myClearColor.g(), myClearColor.b(), myClearColor.a());
    if (myDepthTestWasEnabled)
    {
      myContext->core11fwd->glEnable (GL_DEPTH_TEST);
    }
    else
    {
      myContext->core11fwd->glDisable (GL_DEPTH_TEST);
    }
    myContext->core11fwd->glDepthMask (myDepthWrirtingWasEnablig ? GL_TRUE : GL_FALSE);
    if (myScissorTestWasEnabled)
    {
      myContext->core11fwd->glEnable (GL_SCISSOR_TEST);
    }
    else
    {
      myContext->core11fwd->glDisable (GL_SCISSOR_TEST);
    }
    myContext->core11fwd->glScissor (myScissorBox[0], myScissorBox[1], myScissorBox[2], myScissorBox[3]);
  }

private:

  OpenGl_PBREnvironmentSentry            (const OpenGl_PBREnvironmentSentry& );
  OpenGl_PBREnvironmentSentry& operator= (const OpenGl_PBREnvironmentSentry& );

private:

  const Handle(OpenGl_Context) myContext;
  GLint                        myFBO;
  Handle(OpenGl_ShaderProgram) myShaderProgram;
  NCollection_Vec4<bool>       myColorMask;
  Standard_Boolean             myDepthTestWasEnabled;
  Standard_Boolean             myDepthWrirtingWasEnablig;
  Standard_Boolean             myScissorTestWasEnabled;
  Standard_Integer             myScissorBox[4];
  Standard_Integer             myViewport[4];
  Graphic3d_Vec4               myClearColor;

};

// =======================================================================
// function : Create
// purpose  :
// =======================================================================
Handle(OpenGl_PBREnvironment) OpenGl_PBREnvironment::Create (const Handle(OpenGl_Context)&  theCtx,
                                                             unsigned int                   thePow2Size,
                                                             unsigned int                   theLevelsNumber,
                                                             const TCollection_AsciiString& theId)
{
  if (theCtx->arbFBO == NULL)
  {
    return Handle(OpenGl_PBREnvironment)();
  }

  Handle(OpenGl_PBREnvironment) anEnvironment = new OpenGl_PBREnvironment (theCtx, thePow2Size, theLevelsNumber, theId);
  if (!anEnvironment->IsComplete())
  {
    theCtx->PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_PORTABILITY, 0, GL_DEBUG_SEVERITY_MEDIUM,
                         "Warning: PBR environment is not created. PBR material system will be ignored.");
    anEnvironment->Release (theCtx.get());
    anEnvironment.Nullify();
  }

  return anEnvironment;
}

// =======================================================================
// function : OpenGl_PBREnvironment
// purpose  :
// =======================================================================
OpenGl_PBREnvironment::OpenGl_PBREnvironment (const Handle(OpenGl_Context)&  theCtx,
                                              unsigned int                   thePowOf2Size,
                                              unsigned int                   theSpecMapLevelsNumber,
                                              const TCollection_AsciiString& theId)
: OpenGl_NamedResource (theId),
  myPow2Size (std::max (1u, thePowOf2Size)),
  mySpecMapLevelsNumber (std::max (2u, std::min (theSpecMapLevelsNumber, std::max (1u, thePowOf2Size) + 1))),
  myFBO (OpenGl_FrameBuffer::NO_FRAMEBUFFER),
  myIsComplete (Standard_False),
  myIsNeededToBeBound (Standard_True),
  myCanRenderFloat (Standard_True)
{
  OpenGl_PBREnvironmentSentry aSentry (theCtx);

  myIsComplete = initVAO (theCtx)
              && initTextures (theCtx)
              && initFBO (theCtx);

  if (myIsComplete)
  {
    clear (theCtx);
  }
}

// =======================================================================
// function : Bind
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::Bind (const Handle(OpenGl_Context)& theCtx)
{
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Bind (theCtx);
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Bind (theCtx);
  myIsNeededToBeBound = Standard_False;
}

// =======================================================================
// function : Unbind
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::Unbind (const Handle(OpenGl_Context)& theCtx)
{
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Unbind (theCtx);
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Unbind (theCtx);
  myIsNeededToBeBound = Standard_True;
}

// =======================================================================
// function : Clear
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::Clear (const Handle(OpenGl_Context)& theCtx,
                                   const Graphic3d_Vec3&         theColor)
{
  OpenGl_PBREnvironmentSentry aSentry (theCtx);
  clear (theCtx, theColor);
}

// =======================================================================
// function : Bake
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::Bake (const Handle(OpenGl_Context)& theCtx,
                                  const Handle(OpenGl_Texture)& theEnvMap,
                                  Standard_Boolean              theZIsInverted,
                                  Standard_Boolean              theIsTopDown,
                                  Standard_Size                 theDiffMapNbSamples,
                                  Standard_Size                 theSpecMapNbSamples,
                                  Standard_ShortReal            theProbability)
{
  Standard_ProgramError_Raise_if (theEnvMap.IsNull(), "'Bake' function of 'OpenGl_PBREnvironment' can't work without source environment map")
  Standard_RangeError_Raise_if (theProbability > 1.f || theProbability < 0.f, "'probability' parameter in 'Bake' function of 'OpenGl_PBREnvironment' must be in range [0, 1]")
  Unbind (theCtx);
  OpenGl_PBREnvironmentSentry aSentry (theCtx);
  bake (theCtx, theEnvMap, theZIsInverted, theIsTopDown, theDiffMapNbSamples, theSpecMapNbSamples, theProbability);
}

// =======================================================================
// function : SizesAreDifferent
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::SizesAreDifferent (unsigned int thePow2Size,
                                               unsigned int theSpecMapLevelsNumber) const
{
  thePow2Size = std::max (1u, thePow2Size);
  theSpecMapLevelsNumber = std::max (2u, std::min (theSpecMapLevelsNumber, std::max (1u, thePow2Size) + 1));
  return myPow2Size != thePow2Size
      || mySpecMapLevelsNumber != theSpecMapLevelsNumber;
}

// =======================================================================
// function : Release
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::Release (OpenGl_Context* theCtx)
{
  if (myFBO != OpenGl_FrameBuffer::NO_FRAMEBUFFER)
  {
    if (theCtx != NULL
     && theCtx->IsValid())
    {
      theCtx->arbFBO->glDeleteFramebuffers (1, &myFBO);
    }
    myFBO = OpenGl_FrameBuffer::NO_FRAMEBUFFER;
  }
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Release (theCtx);
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Release (theCtx);
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseFallback].Release (theCtx);
  myVBO.Release (theCtx);
}

// =======================================================================
// function : ~OpenGl_PBREnvironment
// purpose  :
// =======================================================================
OpenGl_PBREnvironment::~OpenGl_PBREnvironment()
{
  Release (NULL);
}

// =======================================================================
// function : initTextures
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::initTextures (const Handle(OpenGl_Context)& theCtx)
{
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Sampler()->Parameters()->SetTextureUnit (theCtx->PBRSpecIBLMapTexUnit());
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Sampler()->Parameters()->SetTextureUnit (theCtx->PBRDiffIBLMapSHTexUnit());
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Sampler()->Parameters()->SetFilter (Graphic3d_TOTF_TRILINEAR);
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Sampler()->Parameters()->SetFilter (Graphic3d_TOTF_NEAREST);
  myIBLMaps[OpenGl_TypeOfIBLMap_Specular] .Sampler()->Parameters()->SetLevelsRange (mySpecMapLevelsNumber - 1);
  myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseFallback].Sampler()->Parameters()->SetFilter (Graphic3d_TOTF_NEAREST);

  // NVIDIA's driver didn't work properly with 3 channel texture for diffuse SH coefficients so that alpha channel has been added
  if (!myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Init (theCtx,
                                                      OpenGl_TextureFormat::FindFormat (theCtx, Image_Format_RGBAF, false),
                                                      Graphic3d_Vec2i (9, 1), Graphic3d_TOT_2D))
  {
    Message::SendFail() << "OpenGl_PBREnvironment, DiffuseSH texture creation failed";
    return false;
  }

  if (!myIBLMaps[OpenGl_TypeOfIBLMap_Specular].InitCubeMap (theCtx, Handle(Graphic3d_CubeMap)(),
                                                            Standard_Size(1) << myPow2Size, Image_Format_RGB, true, false))
  {
    Message::SendFail() << "OpenGl_PBREnvironment, Specular texture creation failed";
    return false;
  }

  if (!myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseFallback].Init (theCtx,
                                                            OpenGl_TextureFormat::FindFormat (theCtx, Image_Format_RGBA, false),
                                                            Graphic3d_Vec2i (10, 4), Graphic3d_TOT_2D))
  {
    Message::SendFail() << "OpenGl_PBREnvironment, DiffuseFallback texture creation failed";
    return false;
  }

  return true;
}

// =======================================================================
// function : initVAO
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::initVAO (const Handle(OpenGl_Context)& theCtx)
{
  const float aVertexPos[] =
  {
    -1.f, -1.f, 0.f, 0.f,
     1.f, -1.f, 0.f, 0.f,
    -1.f,  1.f, 0.f, 0.f,
     1.f,  1.f, 0.f, 0.f
  };
  return myVBO.Init (theCtx, 4, 4, aVertexPos);
}

// =======================================================================
// function : initFBO
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::initFBO (const Handle(OpenGl_Context)& theCtx)
{
  theCtx->arbFBO->glGenFramebuffers (1, &myFBO);
  return checkFBOComplentess (theCtx);
}

// =======================================================================
// function : processDiffIBLMap
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::processDiffIBLMap (const Handle(OpenGl_Context)& theCtx,
                                               const BakingParams* theDrawParams)
{
  const OpenGl_TypeOfIBLMap aRendMapId = myCanRenderFloat ? OpenGl_TypeOfIBLMap_DiffuseSH : OpenGl_TypeOfIBLMap_DiffuseFallback;
  Image_PixMap anImageF;
  if (!myCanRenderFloat)
  {
    anImageF.InitZero (Image_Format_RGBAF, myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].SizeX(), myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].SizeY());
  }

  theCtx->arbFBO->glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                          myIBLMaps[aRendMapId].TextureId(), 0);
  const Standard_Integer aViewport[4] = { 0, 0, 9, myCanRenderFloat ? 1 : 3 };
  theCtx->ResizeViewport(aViewport);
  if (theDrawParams != NULL)
  {
    if (!theCtx->ShaderManager()->BindPBREnvBakingProgram (aRendMapId))
    {
      return false;
    }

    const Handle(OpenGl_ShaderProgram)& aProg = theCtx->ActiveProgram();
    aProg->SetSampler (theCtx, "uEnvMap", theCtx->PBRSpecIBLMapTexUnit());
    aProg->SetUniform (theCtx, "uZCoeff", theDrawParams->IsZInverted ? -1 :  1);
    aProg->SetUniform (theCtx, "uYCoeff", theDrawParams->IsTopDown   ?  1 : -1);
    aProg->SetUniform (theCtx, "uSamplesNum", Standard_Integer(theDrawParams->NbDiffSamples));

    myVBO.BindAttribute (theCtx, Graphic3d_TOA_POS);
    theCtx->core11fwd->glDrawArrays (GL_TRIANGLE_STRIP, 0, 4);
    myVBO.UnbindAttribute (theCtx, Graphic3d_TOA_POS);

    if (!myCanRenderFloat)
    {
      // unpack RGBA8 values to floats
      Image_PixMap anImageIn;
      anImageIn.InitZero (myCanRenderFloat ? Image_Format_RGBAF : Image_Format_RGBA, aViewport[2], aViewport[3]);
      theCtx->core11fwd->glReadPixels (0, 0, aViewport[2], aViewport[3],
                                       GL_RGBA, myCanRenderFloat ? GL_FLOAT : GL_UNSIGNED_BYTE, anImageIn.ChangeData());
      const GLenum anErr = theCtx->core11fwd->glGetError();
      if (anErr != GL_NO_ERROR)
      {
        theCtx->PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_ERROR, 0, GL_DEBUG_SEVERITY_HIGH,
                             TCollection_AsciiString ("Unable to read PBR baking diffuse texture. Error ") + OpenGl_Context::FormatGlError (anErr));
      }
      for (Standard_Size aValIter = 0; aValIter < anImageIn.SizeX(); ++aValIter)
      {
        Graphic3d_Vec4 aVal;
        if (myCanRenderFloat)
        {
          aVal = anImageIn.Value<Graphic3d_Vec4> (0, aValIter);
        }
        else
        {
          const int32_t aPacked[3] = { anImageIn.Value<int32_t> (2, aValIter), anImageIn.Value<int32_t> (1, aValIter), anImageIn.Value<int32_t> (0, aValIter) };
          aVal[0] = aPacked[0] / 2147483647.0f;
          aVal[1] = aPacked[1] / 2147483647.0f;
          aVal[2] = aPacked[2] / 2147483647.0f;
        }
        anImageF.ChangeValue<Graphic3d_Vec4> (0, aValIter) = aVal;
      }
    }
  }
  else
  {
    if (myCanRenderFloat)
    {
      theCtx->core11fwd->glClear (GL_COLOR_BUFFER_BIT);

      theCtx->core11fwd->glEnable (GL_SCISSOR_TEST);
      theCtx->core11fwd->glClearColor (0.f, 0.f, 0.f, 1.f);
      theCtx->core11fwd->glScissor (1, 0, 8, 1);
      theCtx->core11fwd->glClear (GL_COLOR_BUFFER_BIT);
      theCtx->core11fwd->glDisable (GL_SCISSOR_TEST);
    }
    else
    {
      anImageF.ChangeValue<Graphic3d_Vec4> (0, 0) = Graphic3d_Vec4 (1.0f);
      for (Standard_Size aValIter = 1; aValIter < anImageF.SizeX(); ++aValIter)
      {
        anImageF.ChangeValue<Graphic3d_Vec4> (0, aValIter) = Graphic3d_Vec4 (0.0f, 0.0f, 0.0f, 1.0f);
      }
    }
  }

  if (!myCanRenderFloat)
  {
    if (!myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].Init (theCtx,
                                                        OpenGl_TextureFormat::FindFormat (theCtx, Image_Format_RGBAF, false),
                                                        Graphic3d_Vec2i (9, 1), Graphic3d_TOT_2D, &anImageF))
    {
      Message::SendFail() << "OpenGl_PBREnvironment, DiffuseSH texture update failed";
      return false;
    }
  }

  return true;
}

// =======================================================================
// function : processSpecIBLMap
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::processSpecIBLMap (const Handle(OpenGl_Context)& theCtx,
                                               const BakingParams* theDrawParams)
{
  if (theDrawParams != NULL)
  {
    if (!theCtx->ShaderManager()->BindPBREnvBakingProgram (OpenGl_TypeOfIBLMap_Specular))
    {
      return false;
    }

    const Handle(OpenGl_ShaderProgram)& aProg = theCtx->ActiveProgram();
    const float aSolidAngleSource = float(4.0 * M_PI / (6.0 * float(theDrawParams->EnvMapSize * theDrawParams->EnvMapSize)));
    aProg->SetSampler (theCtx, "uEnvMap", theCtx->PBRSpecIBLMapTexUnit());
    aProg->SetUniform (theCtx, "uZCoeff", theDrawParams->IsZInverted ? -1 :  1);
    aProg->SetUniform (theCtx, "uYCoeff", theDrawParams->IsTopDown   ?  1 : -1);
    aProg->SetUniform (theCtx, "occNbSpecIBLLevels",   Standard_Integer(mySpecMapLevelsNumber));
    aProg->SetUniform (theCtx, "uEnvSolidAngleSource", aSolidAngleSource);
    myVBO.BindAttribute (theCtx, Graphic3d_TOA_POS);
  }

  const bool canRenderMipmaps = theCtx->hasFboRenderMipmap;
  const OpenGl_TextureFormat aTexFormat = OpenGl_TextureFormat::FindSizedFormat (theCtx, myIBLMaps[OpenGl_TypeOfIBLMap_Specular].SizedFormat());
#if !defined(GL_ES_VERSION_2_0)
  const GLint anIntFormat = aTexFormat.InternalFormat();
#else
  // ES 2.0 does not support sized formats and format conversions - them detected from data type
  const GLint anIntFormat = theCtx->IsGlGreaterEqual (3, 0) ? aTexFormat.InternalFormat() : aTexFormat.PixelFormat();
#endif

  for (int aLevelIter = mySpecMapLevelsNumber - 1;; --aLevelIter)
  {
    const Standard_Integer aSize = 1 << (myPow2Size - aLevelIter);
    const Standard_Integer aViewport[4] = { 0, 0, aSize, aSize };
    theCtx->ResizeViewport (aViewport);
    if (theDrawParams != NULL)
    {
      const Standard_Integer aNbSamples = Standard_Integer(Graphic3d_PBRMaterial::SpecIBLMapSamplesFactor (theDrawParams->Probability,
                                                                                                           aLevelIter / float (mySpecMapLevelsNumber - 1)) * theDrawParams->NbSpecSamples);
      theCtx->ActiveProgram()->SetUniform (theCtx, "uSamplesNum",   aNbSamples);
      theCtx->ActiveProgram()->SetUniform (theCtx, "uCurrentLevel", aLevelIter);
    }

    for (Standard_Integer aSideIter = 0; aSideIter < 6; ++aSideIter)
    {
      theCtx->arbFBO->glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + aSideIter,
                                              myIBLMaps[OpenGl_TypeOfIBLMap_Specular].TextureId(), canRenderMipmaps ? aLevelIter : 0);
      if (theDrawParams != NULL)
      {
        theCtx->ActiveProgram()->SetUniform(theCtx, "uCurrentSide", aSideIter);
        theCtx->core11fwd->glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
      }
      else
      {
        theCtx->core11fwd->glClear(GL_COLOR_BUFFER_BIT);
      }

      if (!canRenderMipmaps
        && aLevelIter != 0)
      {
        myIBLMaps[OpenGl_TypeOfIBLMap_Specular].Bind (theCtx, Graphic3d_TextureUnit_1);
        theCtx->core20fwd->glCopyTexImage2D (GL_TEXTURE_CUBE_MAP_POSITIVE_X + aSideIter, aLevelIter, anIntFormat, 0, 0, (GLsizei )aSize, (GLsizei )aSize, 0);
        myIBLMaps[OpenGl_TypeOfIBLMap_Specular].Unbind (theCtx, Graphic3d_TextureUnit_1);
        const GLenum anErr = theCtx->core11fwd->glGetError();
        if (anErr != GL_NO_ERROR)
        {
          theCtx->PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_ERROR, 0, GL_DEBUG_SEVERITY_HIGH,
                               TCollection_AsciiString ("Unable to copy cubemap mipmap level. Error ") + OpenGl_Context::FormatGlError (anErr));
        }
      }
    }

    if (aLevelIter == 0)
    {
      break;
    }
  }

  if (theDrawParams != NULL)
  {
    myVBO.UnbindAttribute (theCtx, Graphic3d_TOA_POS);
  }

  return true;
}

// =======================================================================
// function : checkFBOCompletness
// purpose  :
// =======================================================================
bool OpenGl_PBREnvironment::checkFBOComplentess (const Handle(OpenGl_Context)& theCtx)
{
  myCanRenderFloat = true;
  theCtx->arbFBO->glBindFramebuffer (GL_FRAMEBUFFER, myFBO);
  theCtx->arbFBO->glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                          myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseSH].TextureId(), 0);
  if (theCtx->arbFBO->glCheckFramebufferStatus (GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
  {
    // Some WebGL 1.0 and OpenGL ES 2.0 implementations support float textures which cannot be used as render targets.
    // This capability could be exposed by WEBGL_color_buffer_float/EXT_color_buffer_float extensions,
    // but the simplest way is just to check FBO status.
    // The fallback solution involves rendering into RGBA8 texture with floating values packed,
    // and using glReadPixels() + conversion + texture upload of computed values.
    myCanRenderFloat = false;
    theCtx->arbFBO->glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
                                            myIBLMaps[OpenGl_TypeOfIBLMap_DiffuseFallback].TextureId(), 0);
    if (theCtx->arbFBO->glCheckFramebufferStatus (GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
      Message::SendTrace() << "OpenGl_PBREnvironment, incomplete FBO for diffuse map";
      return false;
    }
  }

  for (Standard_Integer aSideIter = 0; aSideIter < 6; ++aSideIter)
  {
    for (unsigned int aLevel = 0; aLevel < mySpecMapLevelsNumber; ++aLevel)
    {
      if (!theCtx->hasFboRenderMipmap
        && aLevel != 0)
      {
        continue;
      }

      theCtx->arbFBO->glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + aSideIter,
                                              myIBLMaps[OpenGl_TypeOfIBLMap_Specular].TextureId(), aLevel);
      if (theCtx->arbFBO->glCheckFramebufferStatus (GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
      {
        Message::SendTrace() << "OpenGl_PBREnvironment, incomplete FBO for specular map " << aSideIter << " "<< aLevel;
        return false;
      }
    }
  }
  return true;
}

// =======================================================================
// function : bake
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::bake (const Handle(OpenGl_Context)& theCtx,
                                  const Handle(OpenGl_Texture)& theEnvMap,
                                  Standard_Boolean              theZIsInverted,
                                  Standard_Boolean              theIsTopDown,
                                  Standard_Size                 theDiffNbSamples,
                                  Standard_Size                 theSpecNbSamples,
                                  Standard_ShortReal            theProbability)
{
  myIsNeededToBeBound = Standard_True;

  theEnvMap->Bind (theCtx, theCtx->PBRSpecIBLMapTexUnit());
  theCtx->arbFBO->glBindFramebuffer (GL_FRAMEBUFFER, myFBO);

  OSD_Timer aTimer;
  aTimer.Start();
  BakingParams aDrawParams;
  aDrawParams.NbSpecSamples = theSpecNbSamples;
  aDrawParams.NbDiffSamples = theDiffNbSamples;
  aDrawParams.EnvMapSize    = theEnvMap->SizeX();
  aDrawParams.Probability   = theProbability;
  aDrawParams.IsZInverted   = theZIsInverted;
  aDrawParams.IsTopDown     = theIsTopDown;
  if (processSpecIBLMap (theCtx, &aDrawParams)
   && processDiffIBLMap (theCtx, &aDrawParams))
  {
    Message::SendTrace(TCollection_AsciiString()
      + "IBL " + myIBLMaps[OpenGl_TypeOfIBLMap_Specular].SizeX() + "x" + myIBLMaps[OpenGl_TypeOfIBLMap_Specular].SizeY()
      + " is baked in " + aTimer.ElapsedTime() + " s");
  }
  else
  {
    theCtx->PushMessage (GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_PERFORMANCE, 0, GL_DEBUG_SEVERITY_HIGH,
      TCollection_AsciiString("Error: baking PBR environment ") + myIBLMaps[OpenGl_TypeOfIBLMap_Specular].SizeX()
      + "x" + myIBLMaps[OpenGl_TypeOfIBLMap_Specular].SizeY() + " takes too much time!.");
    clear (theCtx, Graphic3d_Vec3(1.0f));
  }

  theEnvMap->Unbind (theCtx, theCtx->PBREnvLUTTexUnit());
}

// =======================================================================
// function : clear
// purpose  :
// =======================================================================
void OpenGl_PBREnvironment::clear (const Handle(OpenGl_Context)& theCtx,
                                   const Graphic3d_Vec3&         theColor)
{
  myIsNeededToBeBound = Standard_True;
  theCtx->arbFBO->glBindFramebuffer (GL_FRAMEBUFFER, myFBO);
  theCtx->core11fwd->glClearColor (theColor.r(), theColor.g(), theColor.b(), 1.f);

  processSpecIBLMap (theCtx, NULL);
  processDiffIBLMap (theCtx, NULL);
}