OpenGL Extension Handling

Author: eilemann@gmail.com
State:

• Implemented in 0.5
• Upgraded to GLEW 1.5.7 in 1.0-alpha

Overview

Equalizer uses GLEW for OpenGL extension handling, particularly the GLEW MX implementation for multiple context support.

Implementation

Each eq::Window has a GLEWContext. This context can be obtained by using glewGetContext on the window or channel. GLEW MX uses this function to dispatch the functions to the correct context. Equalizer (re-)initializes the GLEW context whenever a new OpenGL context is set on the window.

Each eq::Pipe has a WGLEWContext. This context is intended to be used for generic functions needed during window creation, e.g., for the WGL_NV_gpu_affinity extension used to create a GPU-specific rendering context. Note that this is an abstraction for WGL, not OpenGL functions.

Usage

Extended OpenGL functions called from a window or channel instance can be called directly. GLEW will call the object's glewGetContext to obtain the correct context.

Extended OpenGL functions called from another place need to have the macro or function glewGetContext that returns the pointer to the GLEWContext of the appropriate window.

Examples

void eqPly::Channel::_drawModel( const Model* model )
{
    ...
    glUseProgram( program );
    ...
}



// state has GLEWContext* from window
define glewGetContext state.glewGetContext

/*  Set up rendering of the leaf nodes.  */
void VertexBufferLeaf::setupRendering( VertexBufferState& state,
                                       GLuint* data ) const
{
    ...
    glBindBuffer( GL_ARRAY_BUFFER, data[VERTEX_OBJECT] );
    glBufferData( GL_ARRAY_BUFFER, _vertexLength * sizeof( Normal ),
                    &_globalData.normals[_vertexStart], GL_STATIC_DRAW );
    ...
}

API

    WGLEWContext* eq::Pipe::wglewGetContext();
    GLEWContext* eq::Window::glewGetContext();
    GLEWContext* eq::Channel::glewGetContext();

File Format

No Changes.

Open Issues

None known

Changes to GLEW

• 4092: Some glxew functions used in glew.c where not defined in glxew.h.
• 3989: The package nvidia-glx-185-dev defines GLXEvent without the safeguard definition GLX_VERSION_1_3. Disable the definition in glxew.h, unless explicitely requested by defining EQ_NEED_GLXEVENT.