Graphics Reference
In-Depth Information
The process this algorithm uses is illustrated in Figure 14-7, which shows
each of the steps that goes into producing the final image. As you can see
in this figure, the object is first rendered in black to the render target. That
render target is then blurred into a second render target in the next pass.
The blurred render target is then blurred again, with an expanded blur
kernel going back into the original render target. At the end, that blurred
render target is blended with the original scene. The amount of bloom can
be increased by ping-ponging the blur targets over and over. The shader
code for the blur steps is the same as in the previous example; the only
difference is that the blur step is being increased for each pass.
Figure 14-7
Light Bloom Stages
A large variety of other image postprocessing algorithms can be performed
using a combination of FBOs and shaders. Some other common
techniques include tone mapping, selective blurring, distortion, screen
transitions, and depth of field. Using the techniques shown here, you can
start to implement other postprocessing algorithms using shaders.
A technique that is used to produce many effects, such as shadow mapping
and reflections, is projective texturing. To introduce the topic of projective
texturing, we provide an example of rendering a projective spotlight.
Most of the complexity in using projective texturing derives from the
mathematics that goes into calculating the projective texture coordinates.
The method shown here could also be used to produce texture coordinates
for shadow mapping or reflections. The example offered here is found
