Fog Parameters
Fog parameters are controlled through device render states. Both pixel and vertex fog types support all the fog formulas introduced in Fog Formulas. The D3DFOGMODE enumerated type defines constants that you can use to identify the fog formula you want Microsoft® Direct3D® to use. The D3DRS_FOGTABLEMODE render state controls the fog mode that Direct3D uses for pixel fog, and the D3DRS_FOGVERTEXMODE render state controls the mode for vertex fog.
When using the linear fog formula, you set the starting and ending distances through the D3DRS_FOGSTART and D3DRS_FOGEND render states. How the system interprets these values depends on the type of fog your application uses — pixel or vertex fog — and, when using pixel fog, if z-based or w-based depth is being used. For information z- and w-based pixel fog, see Eye-Relative vs. Z-Based Depth. The following table shows fog types and their start and end units.
| Fog type | Fog start/end unit |
|---|---|
| Pixel (Z) | Device space [0.0,1.0] |
| Pixel (W) | Camera space |
| Vertex | Camera space |
The D3DRS_FOGDENSITY render state controls the fog density applied when an exponential fog formula is enabled. Fog density is essentially a weighting factor, ranging from 0.0 to 1.0 (inclusive), that scales the distance value in the exponent.
The color that the system uses for fog blending is controlled through the D3DRS_FOGCOLOR device render state. For more information, see Fog Color and Fog Blending.
See Also
Last updated on Thursday, April 08, 2004
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