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.TH "icetDrawFrame" "3" "September 22, 2014" "\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
The \fIbackground_color\fP
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\&.
.PP
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 \fBICET_CORRECT_COLORED_BACKGROUND\fP
feature is
enabled, this background color is blended back into the final composited
image.
.PP
.SH Return Value

.PP
On each .igdisplay processdisplay
process (as defined by
\fBicetAddTile\fP),
\fBicetDrawFrame\fP
returns the fully composited
image in an \fBIceTImage\fP
object. 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 or composites a frame. Do not use this image after
the next call to \fBicetDrawFrame\fP
(unless you have changed the \fBIceT \fP
context).
.PP
.SH Errors

.PP
.TP
\fBICET_INVALID_OPERATION\fP
 Raised 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
feature is enabled.
.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),
\fIicetCompositeImage\fP(3),
\fIicetDrawCallback\fP(3),
\fIicetGLDrawFrame\fP(3),
\fIicetSingleImageStrategy\fP(3),
\fIicetStrategy\fP(3)
.PP
.\" NOTE: This file is generated, DO NOT EDIT.