Existing OCCT path tracing engine used very simple additive material (BSDF) model, so it was possible to reproduce
behavior only of very basic materials such as metal, glass, or plastic. However, some important in CAD industry
materials like car paint or ceramic could not be modeled well. In this patch, OCCT BSDF was significantly improved
by replacing additive model with two-layered scattering model. Therefore, we have base diffuse, glossy, or transmissive
layer, covered by one glossy/specular coat. The layers themselves have no thickness; they can simply reflect light or
transmits it to the layer under it. Balancing different combinations of layer properties can produce a wide range of
different effects. At the same time, disabling the first (coat) layer allows to keep full compatibility with previously
supported scattering model. All new parameters are available via 'vbsdf' command.
Location of new sample for few material examples:
samples\tcl\pathtrace_materials.tcl
Fix shader compilation issue.
Fix test case sample_ball_alpha.
Shaders_PathtraceBase_fs.pxx - regenerate resource from origin
Generation of header files from resource files was added to CMake and genproj procedures.
Message_MsgFile has been extended with new method ::LoadFromString()
for loading messages from embedded resources.
Message_MsgFile::LoadFromString() is now a preferred way
for loading message resources by application
as alternative to environment variables.
TObje/TObj.msg is now embedded into TObj_Application.cxx.
TObj_Application now loads its global messages
on instantiation of the first class instance.
UnitsAPI/Lexi_Expr.dat now completely embedded into Units_Lexicon.cxx.
UnitsAPI/Units.dat now embedded into Units_UnitsDictionary.cxx
but can be regenerated from resource file.
The definition of the following units have been removed:
benne à charbon, calorie (diététique).
Unused message files XSMessage/IGES.us and IGES.fr have been removed.
Related code IGESData.cxx has been removed as well.
XSMessage/XSTEP.us is now embedded into Interface_StaticStandards.cxx
and used for fallback initialization in case when file resources
defined by CSF_XSMessage environment variable are missing.
SHMessage/SHAPE.us is now embedded into ShapeExtend.cxx
and used for fallback initialization in case when file resources
defined by CSF_XHMessage environment variable are missing.
Duplicating code has been removed from ShapeProcess_OperLibrary.cxx.
Shaders/Declarations.glsl and Shaders/DeclarationsImpl.glsl
are now embedded into OpenGl_ShaderProgram.cxx.
CSF_ShadersDirectory is no more required for using OCCT 3D Viewer.
Ray-Tracing GLSL programs from Shaders are now embedded into OpenGl_View_Raytrace.cxx.
File resources are still used instead of embedded programs
when CSF_ShadersDirectory is defined, but this functionality
is intended for OCCT development.
Enumeration Graphic3d_ShaderProgram::ShaderName_Phong
demonstrating custom GLSL program usage has been removed.
This commit provides useful functionality for path tracing rendering core.
1) Graphic3d_RenderingParams class was extended with additional AdaptiveScreenSampling option (disabled by default).
If this option is enabled, path tracing tries to adjust the number of samples for different screen areas.
In this way, the more complex areas (from the point of light conditions) are sampled more intensively,
while the simple areas are sampled very rarely.
For example, caustics and glossy reflections are typical candidates for more precise sampling.
In general, this allows to equalize image convergence and not to waste resources for already converged areas.
It is also possible to visualize sampling densities by enabling ShowSamplingTiles option
(activating and deactivating this option does not affect on the accumulated image).
2) Mixing OpenGL and ray-tracing output has been changed.
Now blending is performed using OpenGL functionality, while ray-tracing shaders only output correct Z-value.
Test case bugs vis bug27083 has been updated,
since the alpha value is now correctly set by Ray-Tracing to 1, opaque.
In frames of this issue binary BVH tree produced by building algorithms was collapsed into 4-ary BVH (QBVH).
The BVH traversal code in GLSL was modified to process such trees correctly.
This allows to implore thread coherence, decrease BVH memory consumption (~2 times), and use traversal stack of the half size.
As a result, ray tracing scalability is improved, as well as rendering performance. For various setups, speedup is 12-18%.
View-projection matrix was added to raytrace shaders (as uniform) in order to compute correct depth values for OpenGL.
For path tracing the additional depth buffer sampler was added to Display.fs program. It allows propagation of depth values from internal FBO to resulting FBO.
The old approach of mixing of OpenGL and ray-tracing graphics was kept in order to keep correct blending of transparent ray-traced objects with non-transparent OpenGL objects.
Replace 64-bit handles of bindless textures by uvec2 type in GLSL code for compatibility with AMD drivers.
OpenGl_View::initProgram() - fix NULL-dereference.
Backside triangles are handled correctly by implementing two-sided lighting model. Ray-tracing shader was optimized (up to 25% performance increase).
Test case for CR25833
This patch eliminates 3 samplers used in ray-tracing mode:
//! Texture buffer of data records of bottom-level BVH nodes.
Handle(OpenGl_TextureBufferArb) myObjectNodeInfoTexture;
//! Texture buffer of minimum points of bottom-level BVH nodes.
Handle(OpenGl_TextureBufferArb) myObjectMinPointTexture;
//! Texture buffer of maximum points of bottom-level BVH nodes.
Handle(OpenGl_TextureBufferArb) myObjectMaxPointTexture;
Serialized data contained in corresponding texture buffers were added to global scene buffers:
//! Texture buffer of data records of high-level BVH nodes.
Handle(OpenGl_TextureBufferArb) mySceneNodeInfoTexture;
//! Texture buffer of minimum points of high-level BVH nodes.
Handle(OpenGl_TextureBufferArb) mySceneMinPointTexture;
//! Texture buffer of maximum points of high-level BVH nodes.
Handle(OpenGl_TextureBufferArb) mySceneMaxPointTexture;
This modifications leads also to small performance improvement (~2%) due to higher texture cache efficiency. Some modifications in traversal function (GLSL code) also improve performance (~3%).
OpenGl_GraphicDriver::Redraw() - do not recompute structures more than required
OpenGl_Workspace::Raytrace() - bind proper FBO before clearing it
Visual3d_View::Redraw() - perform automatic 2nd redraw on device lost
Refraction index passed to raytrace shader.
For transparent objects implemented ray refraction according to refraction index.
Transparent materials modified to look better with refractions.
