In IRIS GL, when drawing to both front and back buffers, blending is done by reading one of the buffers, blending with that color, and then writing the result to both buffers. In OpenGL, however, each buffer is read in turn, blended, and then written.
The following table lists IRIS GL blending functions and their equivalent OpenGL functions.
| IRIS GL Function | OpenGL Function | Meaning |
|---|---|---|
| — | glEnable(GL_BLEND) | Turn on blending. |
| blendfunction | glBlendFunc | Specify a blend function. |
The OpenGL glBlendFunc function and the IRIS GL blendfunction function are almost identical. The following table lists IRIS GL blend factors and their OpenGL equivalents.
| IRIS GL | OpenGL | Notes |
|---|---|---|
| BF_ZERO | GL_ZERO | |
| BF_ONE | GL_ONE | |
| BF_SA | GL_SRC_ALPHA | |
| BF_MSA | GL_ONE_MINUS_SRC_ALPHA | |
| BF_DA | GL_DST_ALPHA | |
| BF_MDA | GL_ONE_MINUS_DST_ALPHA | |
| BF_SC | GL_SRC_COLOR | |
| BF_MSC | GL_ONE_MINUS_SRC_COLOR | Destination only. |
| BF_DC | GL_DST_COLOR | Source only. |
| BF_MDC | GL_ONE_MINUS_DST_COLOR | Source only. |
| BF_MIN_SA_MDA | GL_SRC_ALPHA_SATURATE |