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occt/samples/webgl/ReadMe.md
kgv 565baee64b 0031070: Configuration - fix building issues when using Emscripten toolchain 
Handled __EMSCRIPTEN__ macros to:
- Workaround atomics (__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 is undefined, but GCC atomics are provided).
- Suppress non-standard header <sys/signal.h> warning.
- Return OSD_LinuxREDHAT.
- Avoid inclusion of XLib headers.
- Skip fontconfig library.
- Enable EGL+GLES path (translated by Emscripten into WebGL).
- Skip eglCreatePbufferSurface() not implemented by Emscripten EGL.

Fixed Graphic3d_Vec4.hxx usage within Quantity_ColorRGBA.hxx.

OpenGl_ShaderManager::defaultGlslVersion() now prefers GLSL 300 es when WebGL 2.0 is available,
as there no any OpenGL ES greater than 3.0 emulation so far.

Shaders_Declarations.glsl - added workaround for GLSL compilation on WebGL 1.0
by defining Light properties accessors as macros instead of functions
('[]' : Index expression must be constant).

OpenGl_FrameBuffer::Init() - added workaround for initialization of GL_DEPTH24_STENCIL8
depth-stencil attachment on WebGL 1.0 + GL_WEBGL_depth_texture extension.

OpenGl_Context::Vec4FromQuantityColor() now considers myIsSRgbActive flag
to handle use case, when Immediate Layer is drawn directly into window buffer,
which is not sRGB-ready.

Added new sample - OCCT WebGL viewer.
2019-10-27 00:43:07 +03:00

1.6 KiB
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OCCT WebGL Viewer sample

This sample demonstrates simple way of using OCCT libraries in Web application written in C++ and translated into WebAssembly module using Emscripten SDK (emsdk): https://emscripten.org/

Sample consists of the Open CASCADE 3D Viewer with a button for opening a model in BREP format. The sample requires a WebGL 2.0 capable browser supporting WebAssembly 1.0 (Wasm).

Installation and configuration:

  1. Install Emscripten SDK and activate minimal configuration (Python, Java and CLang) following emsdk documentation. Activate also MinGW when building sample on Windows host.
  2. Build (using emsdk) or download FreeType static library.
  3. Configure CMake for building Open CASCADE Technology (OCCT) static libraries (BUILD_LIBRARY_TYPE="Static"). For this, activate emsdk command prompt, configure CMake for building OCCT using cross-compilation toolchain, disable BUILD_MODULE_Draw.
  4. Perform building and installation steps.
    > ${EMSDK}/fastcomp/emscripten/cmake/Modules/Platform/Emscripten.cmake
  1. Configure CMake for building this WebGL sample using emsdk with paths to OCCT and FreeType. Perform building and installation steps.
  2. Copy data/occ/Ball.brep from OCCT into "samples" folder within WebGL sample installation path.
  3. Navigate to installation folder and start web server from it; Python coming with emsdk can be used for this purpose:
    > python -m SimpleHTTPServer 8080
  1. Open compatible browser and enter path taking into account your web server settings:
    > http://localhost:8080/occt-webgl-sample.html