icetGLDrawFrame(3)

NAME
icetGLDrawFrame -- renders and composites a frame using OpenGL

Synopsis

#include <IceTGL.h>

void icetGLDrawFrame( void );

Description

Initiates a frame draw using the current OpenGL transformation matrices (modelview and projection).

Before IceT may render an image, the tiled display needs to be defined (using icetAddTile), the drawing function needs to be set (using icetGLDrawCallback), and composite strategy must be set (using icetStrategy). The single image sub-strategy may also optionally be set (using icetSingleImageStrategy).

All processes in the current IceT context must call icetGLDrawFrame for it to complete.

The OpenGL projection matrix and modelview matrix must be set using glLoadMatrix or a number of other functions. Likewise, the OpenGL background color must be set with glClearColor. IceT will use the matrices to determine what pixels need to be rendered and composited. IceT will also modify the projection matrix to project onto (or in between) tiles.

If ICET_GL_DISPLAY is enabled, then the fully composited image is written back to the OpenGL framebuffer for display. It is the application's responsibility to synchronize the processes and swap front and back buffers. If the OpenGL background color is set to something other than black, ICET_GL_DISPLAY_COLORED_BACKGROUND should also be enabled. Displaying with ICET_GL_DISPLAY_COLORED_BACKGROUND disabled may be slightly faster (depending on graphics hardware) but can result in black rectangles in the background. If ICET_GL_DISPLAY_INFLATE is enabled and the size of the renderable window (determined by the current OpenGL viewport) is greater than that of the tile being displayed, then the image will first be ``inflated'' to the size of the actual display. This inflation will be assisted by texture hardware if ICET_GL_DISPLAY_INFLATE_WITH_HARDWARE is on. If ICET_GL_DISPLAY_INFLATE is disabled, the image is drawn at its original resolution at the lower left corner of the display.

The image remaining in the frame buffer is undefined if ICET_GL_DISPLAY is disabled or the process is not displaying a tile.

Errors

ICET_INVALID_OPERATION
     Raised if the icetGLInitialize has not been called or if the drawing callback has not been set. Also can be raised if icetGLDrawFrame is called recursively, probably from within the drawing callback.

ICET_OUT_OF_MEMORY
     Not enough memory left to hold intermittent frame buffers and other temporary data.

icetGLDrawFrame may also indirectly raise an error if there is an issue with the strategy or callback.

Warnings

None.

Bugs

If compositing with color blending on, the image returned may have a black background instead of the background_color requested. This can be corrected by blending the returned image over the desired background. This will be done for you if the ICET_CORRECT_COLORED_BACKGROUND is on.

Copyright
Copyright (C)2003 Sandia Corporation

Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains certain rights in this software.

This source code is released under the New BSD License.

See Also

icetAddTile(3), icetBoundingBox(3), icetBoundingVertices(3), icetDrawFrame(3), icetGLDrawCallback(3), icetSingleImageStrategy(3), icetStrategy(3)