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.TH "icetDrawFrame" "3" "August  9, 2010" "\fBIceT \fPReference" "\fBIceT \fPReference"
.SH NAME

\fBicetDrawFrame \-\- renders and composites a frame\fP
.PP
.SH Synopsis

.PP
#include <IceT.h>
.PP
.TS H
l l l .
\fBIceTImage\fP \fBicetDrawFrame\fP(
	const IceTDouble *	\fIprojection_matrix\fP,
	const IceTDouble *	\fImodelview_matrix\fP,
	const IceTFloat *	\fIbackground_color\fP  );
.TE
.PP
.SH Description

.PP
Initiates a frame draw using the given transformation matrices (modelview 
and projection). If you are using \fbOpenGL \fP,you should probably use the 
\fBicetGLDrawFrame\fP
function and associated 
\fBicetGLDrawCallback\fP\&.
.PP
Before \fBIceT \fPmay render an image, the tiled display needs to be defined 
(using \fBicetAddTile\fP),
the drawing function needs to be set (using 
\fBicetDrawCallback\fP),
and composite strategy must be set (using 
\fBicetStrategy\fP).
The single image sub\-strategy may also optionally 
be set (using \fBicetSingleImageStrategy\fP).
.PP
All processes in the current \fBIceT \fPcontext must call 
\fBicetDrawFrame\fP
for it to complete. 
.PP
During compositing, \fBIceT \fPuses the given \fIprojection_matrix\fP
and 
\fImodelview_matrix\fP,
as well as the bounds given in the last call to 
\fBicetBoundingBox\fP
or \fBicetBoundingVertices\fP,
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, \fBIceT \fPmay clip the geometry in surprising ways. Furthermore, 
\fBIceT \fPwill modify the \fIprojection_matrix\fP
for the drawing callback 
to change the projection onto (or in between) tiles. Thus, you should 
pass the desired \fIprojection_matrix\fP
to \fBicetDrawFrame\fP
and 
then use the version passed to the drawing callback. 
.PP
.SH Return Value

.PP
On each .igdisplay processdisplay
process (as defined by 
\fBicetAddTile\fP,
\fBicetDrawFrame\fP
returns an image of the fully 
composited image. The contents of the image are undefined for any 
non\-display process. 
.PP
If the \fBICET_COMPOSITE_ONE_BUFFER\fP
option is on and both a color 
and depth buffer is specified with \fBicetSetColorFormat\fPand 
\fBicetSetDepthFormat\fP,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. 
.PP
The returned image uses memory buffers that will be reclaimed the next 
time \fBIceT \fPrenders a frame. Do not use this image after the next call to 
\fBicetDrawFrame\fP
(unless you have changed the \fBIceT \fPcontext). 
.PP
.SH Errors

.PP
.TP
\fBICET_INVALID_OPERATION\fP
 Raised if the \fBicetGLInitialize\fP
has not been called or if the 
drawing callback has not been set. Also can be raised if 
\fBicetDrawFrame\fP
is called recursively, probably from within the 
drawing callback. 
.TP
\fBICET_OUT_OF_MEMORY\fP
 Not enough memory left to hold intermittent frame buffers and other 
temporary data. 
.PP
\fBicetDrawFrame\fP
may also indirectly raise an error if there is an 
issue with the strategy or callback. 
.PP
.SH Warnings

.PP
None. 
.PP
.SH Bugs

.PP
If compositing with color blending on, the image returned may have a 
black background instead of the \fIbackground_color\fP
requested. This 
can be corrected by blending the returned image over the desired 
background. This will be done for you if the 
\fBICET_CORRECT_COLORED_BACKGROUND\fP
is on. 
.PP
.SH Copyright

Copyright (C)2003 Sandia Corporation 
.PP
Under the terms of Contract DE\-AC04\-94AL85000 with Sandia Corporation, the 
U.S. Government retains certain rights in this software. 
.PP
This source code is released under the New BSD License. 
.PP
.SH See Also

.PP
\fIicetAddTile\fP(3),
\fIicetBoundingBox\fP(3),
\fIicetBoundingVertices\fP(3),
\fIicetDrawCallback\fP(3),
\fIicetGLDrawFrame\fP(3),
\fIicetSingleImageStrategy\fP(3),
\fIicetStrategy\fP(3)
.PP
.\" NOTE: This file is generated, DO NOT EDIT.