0026711: Visualization, TKOpenGl - support creation of multisampling off-screen FBOs

OpenGl_Texture::Init2DMultisample() - new method to initialize multisampled texture.
Graphic3d_RenderingParams::NbMsaaSamples - add option defining MSAA samples number.

RayTracing will keep using FBO without MSAA, however it is possible to combine
MSAA for rasterization and FSAA for RayTracing.

OpenGl_FrameBuffer constructor has been changed to do not take arguments.
OpenGl_FrameBuffer::Init() method has been extended with mandatory parameters
defining Color and Depth attachment formats
and optional parameter defining number of MSAA parameters.

Draw Harness, add option -msaa to vrenderparams.

src/OpenGl/OpenGl_View.hxx

@@ -545,7 +545,7 @@ private:
   OpenGl_VertexBuffer* initBlitQuad (const Standard_Boolean theToFlip);
 
   //! Blend together views pair into stereo image.
-  void drawStereoPair();
+  void drawStereoPair (OpenGl_FrameBuffer* theDrawFbo);
 
 protected:
 
@@ -599,6 +599,8 @@ protected: //! @name Rendering properties
 
   //! Two framebuffers (left and right views) store cached main presentation
   //! of the view (without presentation of immediate layers).
+  GLint                      myFboColorFormat;        //!< sized format for color attachments
+  GLint                      myFboDepthFormat;        //!< sized format for depth-stencil attachments
   Handle(OpenGl_FrameBuffer) myMainSceneFbos[2];
   Handle(OpenGl_FrameBuffer) myImmediateSceneFbos[2]; //!< Additional buffers for immediate layer in stereo mode.
   OpenGl_VertexBuffer        myFullScreenQuad;        //!< Vertices for full-screen quad rendering.
@@ -1034,6 +1036,7 @@ protected: //! @name fields related to ray-tracing
   Handle(OpenGl_FrameBuffer) myRaytraceFBO2[2];
   //! Framebuffer (FBO) for preliminary OpenGL output.
   Handle(OpenGl_FrameBuffer) myOpenGlFBO;
+  Handle(OpenGl_FrameBuffer) myOpenGlFBO2;
 
   //! Vertex buffer (VBO) for drawing dummy quad.
   OpenGl_VertexBuffer myRaytraceScreenQuad;