Ubuntu Manpage: icetCompositeImage -- composites a pre-rendered image

Provided by: paraview_5.4.1+dfsg3-1_amd64

NAME

       icetCompositeImage -- composites a pre-rendered image

Synopsis

       #include <IceT.h>

       IceTImage icetCompositeImage(
                                       const IceTVoid *     color_buffer,
                                       const IceTVoid *     depth_buffer,
                                       const IceTInt *      valid_pixels_viewport,
                                       const IceTDouble *   projection_matrix,
                                       const IceTDouble *   modelview_matrix,
                                       const IceTFloat *    background_color  );

Description

The icetCompositeImage function takes image buffer data and composites it to a single
image. This function behaves similarly to icetDrawFrame except that instead of using
callback functions to render and retrieve image data, the images are pre-rendered and
passed directly to icetCompositeImage. Although it is more efficient to allow IceT to
determine rendering projections and use callbacks, it is often more convenient for
applications to integrate IceT as a separate compositing step after the rendering.

Before IceT may composite an image, the display needs to be defined (using icetAddTile),
the buffer formats need to be specified (using icetSetColorFormatand
icetSetDepthFormat),and the composite strategy must be set (using icetStrategy). The
single image sub-strategy may also optionally be set (using icetSingleImageStrategy).

All process must call icetCompositeImage for the operation to complete on any process in a
parallel job.

The color_buffer and depth_buffer arguments point to memory buffers that contain the image
data. The image data is always stored in densely packed arrays in row-major order (a.k.a.
x-major order or by scan-lines). The first horizontal scan-line is at the bottom of the
image with subsequent scan-lines moving up. The size of each image buffer is expected to
be the width and the height of the global viewport (which is set indirectly with
icetAddTile). The global viewport is stored in the ICET_GLOBAL_VIEWPORT state variable.
If only one tile is specified, then the width and height of the global viewport will be
the same as this one tile.

The format for color_buffer is expected to be the same as what is set with
icetSetColorFormat.The following formats and their interpretations with respect to
color_buffer are as follows.

ICET_IMAGE_COLOR_RGBA_UBYTE
Each entry is an RGBA color tuple. Each component is valued in the range from 0 to
255 and is stored as an 8-bit integer. The buffer will always be allocated on
memory boundaries such that each color value can be treated as a single 32-bit
integer.

ICET_IMAGE_COLOR_RGBA_FLOAT
Each entry is an RGBA color tuple. Each component is in the range from 0.0 to 1.0
and is stored as a 32-bit float.

ICET_IMAGE_COLOR_NONE
No color values are stored in the image.

Likewise, the format for depth_buffer is expected to be the same as what is set with
icetSetDepthFormat.The following formats and their interpretations with respect to
depth_buffer are as follows.

ICET_IMAGE_DEPTH_FLOAT
Each entry is in the range from 0.0 (near plane) to 1.0 (far plane) and is stored
as a 32-bit float.

ICET_IMAGE_DEPTH_NONE
No depth values are stored in the image.

If the current format does not have a color or depth, then the respective buffer argument
should be set to NULL.

Care should be taken to make sure that the color and depth buffer formats are consistent
to the formats expected by IceT .Mismatched formats will result in garbage images and
possible memory faults.

Also note that when compositing with color blending (icetCompositeMode is set to
ICET_COMPOSITE_MODE_BLEND), the color buffer must be rendered with a black background in
order for the composite to complete correctly. A colored background can later be added
using the background_color as described below.

valid_pixels_viewport is an optional argument that makes it possible to specify a subset
of pixels that are valid. In parallel rendering it is common for a single process to
render geometry in only a small portion of the image, and IceT can take advantage of this
information. If the rendering system identifies such a region, it can be specified with
valid_pixels_viewport.

Like all viewports in IceT ,valid_pixels_viewport is an array of 4 integers in the form
$<x, y, width, height >$.This viewport is given in relation to the image passed in the
color_buffer and depth_buffer arguments. Everything outside of this rectangular region
will be ignored. For example, if the valid_pixels_viewport $<10, 20, 150, 100 >$is given,
then icetCompositeImage will ignore all pixels in the bottom 10 rows, the left 20 columns,
anything above the $160^th$ (10+150) row, and anything to the right of the $120^th$
(20+100) column.

If valid_pixels_viewport is NULL, then all pixels in the input image are assumed to be
valid.

projection_matrix and modelview_matrix are optional arguments that specify the projection
that was used during rendering. When applied to the geometry bounds information given
with icetBoundingBox or icetBoundingVertices, this provides IceT with further information
on local image projections. 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. If these arguments are set to NULL, then geometry projection will not be considered
when determining what parts of images are valid.

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 used to correct
colored backgrounds.

As stated previously, color blended compositing only works correctly if the images are
rendered with a clear black background. Otherwise the background color will be added
multiple times by each process that contains geometry in that pixel. 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), icetCompositeImage
       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 icetCompositeImage
       (unless you have changed the IceT context).

Errors

       ICET_INVALID_VALUE
               An argument is set to NULL where data is required.

       ICET_OUT_OF_MEMORY
               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.

Warnings

       ICET_INVALID_VALUE
               An argument to icetCompositeImage is inconsistent with the current IceT state.

Bugs

       The images provided must match the format expected by IceT or else unpredictable  behavior
       may  occur. The images must also be carefully rendered to follow the provided viewport and
       projections. Images that a color blended must be rendered  with  a  black  background  and
       rendered with the correct alpha value.

       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

       Copyright (C)2014 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.