icetDrawFrame(3) renders and composites a frame


#include <IceT.h>

IceTImage icetDrawFrame(
const IceTDouble *projection_matrix,
const IceTDouble *modelview_matrix,
const IceTFloat *background_color );


Initiates a frame draw using the given transformation matrices (modelview and projection). If you are using OpenGL ,you should probably use the icetGLDrawFrame function and associated icetGLDrawCallback.

Before IceT may render an image, the tiled display needs to be defined (using icetAddTile), the drawing function needs to be set (using icetDrawCallback), 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 icetDrawFrame for it to complete.

During compositing, IceT uses the given projection_matrix and modelview_matrix, as well as the bounds given in the last call to icetBoundingBox or icetBoundingVertices, to determine onto which pixels the local geometry projects. If the given matrices are not the same used in the rendering or the given bounds do not contain the geometry, IceT may clip the geometry in surprising ways. Furthermore, IceT will modify the projection_matrix for the drawing callback to change the projection onto (or in between) tiles. Thus, you should pass the desired projection_matrix to icetDrawFrame and then use the version passed to the drawing callback.

The background_color argument specifies the desired background color for the image. It is given as an array of 4 floating point values specifying, in order, the red, green, blue, and alpha channels of the color in the range from 0.0 to 1.0.

When rendering using a depth buffer, the background color is used to fill in empty regions of images. When rendering using color blending, the background color is changed to transparent black during rendering to prevent the background from being blended multiple times from different renderings. If the ICET_CORRECT_COLORED_BACKGROUND feature is enabled, this background color is blended back into the final composited image.

Return Value

On each .igdisplay processdisplay process (as defined by icetAddTile), icetDrawFrame returns the fully composited image in an IceTImage object. The contents of the image are undefined for any non-display process.

If the ICET_COMPOSITE_ONE_BUFFER option is on and both a color and depth buffer is specified with icetSetColorFormatand icetSetDepthFormat,then the returned image might be missing the depth buffer. The rational behind this option is that often both the color and depth buffer is necessary in order to composite the color buffer, but the composited depth buffer is not needed. In this case, the compositing might save some time by not transferring depth information at the latter stage of compositing.

The returned image uses memory buffers that will be reclaimed the next time IceT renders or composites a frame. Do not use this image after the next call to icetDrawFrame (unless you have changed the IceT context).



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

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

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




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 feature is enabled.


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.