Shadows
In Maya, an individual light source can produce no shadows (default), depth map shadows or raytraced shadows. You can combine depth map shadow casting lights and raytraced shadow casting lights in a scene.

Depth map shadows and ray traced shadows produce similar results, though depth map shadows usually take less time to render. Generally, choose depth map shadows unless they cannot accomplish your visual goal.

Depth Map Shadows
Raytraced Shadows
Solving Shadow Problems

Important Consideration for Dmap Resolution:
The shape nodes for all objects in your scene have a "casts shadows" option in the Render Stats section. By default (with Dmap Auto Focus) the shadow-casting light takes into account the size of every shadow-casting object (with the exception of the spot light). Turning off the "casts shadow" option for selected objects can dramatically affect the apparent resolution of shadows, e.g., the landscape or floor.

Spot lights calculate a depth map restricted to the cone angle. Reducing the cone angle can improve the apparent resolution of the depth map.

If the distance from the light to another shadow casting surface is greater than the depth map distance, that surface is in shadow. Use Mid Dist Dmap is on by default.

Use Dmap Auto Focus
If on, Maya automatically scales the depth map so that it only fills the area of the light's illumination that contains shadow casting objects.

For example, if shadow casting objects are only in the center of a spot light's beam, the depth map only covers the region occupied by those objects. Because the Dmap Resolution is an absolute resolution (that is, pixels, not pixels per inch), decreasing the size of the depth map effectively increases the resolution of the depth map and the quality of the shadows without increasing rendering times.

If off, you can manually scale the depth map within the area of the light's illumination using the Dmap Focus attribute (for point lights and spot lights) or the Dmap Width Focus attribute (for directional lights). Use Dmap Auto Focus is on by default.

Dmap Focus, Dmap Width Focus
The angle (Dmap Focus) or width (Dmap Width Focus) to scale the depth map within the area of the light's illumination. (You can scale the depth map automatically by turning on Use Dmap Auto Focus.)

Because the Dmap Resolution is an absolute resolution (that is, pixels, not pixels per inch), decreasing the size of the depth map effectively increases the resolution of the depth map and the quality of the shadows without increasing rendering times.

Dmap Focus is only available for point lights and spot lights if Use Dmap Auto Focus is off. The slider range is 0 to 360. The default value is 90.

Dmap Width Focus is only available for directional lights if Use Dmap Auto Focus is off. The valid range is 0 to ·. The default value is 100.

Use Light Position
Use Light Position is only available for directional lights. If on, only objects in front of the directional light's icon are lit and cast shadows. If off, objects both in front of and behind the directional light's icon are lit and casts shadows.Use Light Position is only available for directional lights. Use Light Position is off by default.

Dmap Bias
Offsets the depth map toward or away from the light. Adjust the Dmap Bias only if you encounter the following problems and cannot resolve them by adjusting other attributes:

If dark spots or streaks appear on illuminated surfaces, gradually increase the Dmap Bias value until the spots or streaks disappear.
If a shadow appears to be detached from the shadow casting surface, gradually decrease the Dmap Bias value until the shadow looks correct. The slider range is 0 to 1, but you can type in a higher value. The default value is 0.001.

Fog Shadow Intensity
Controls the darkness of shadows appearing in illuminated (light) fog. The valid range is 1 to 10. The default value is 1.

Fog Shadow Samples
Controls the graininess of shadows appearing in illuminated (light) fog. Increasing Fog Shadows Samples also increases rendering times, so set it to the lowest value that produces acceptable results. Shadows that are cast from very narrow objects into illuminated fog may shift during an animation. In this case, increase the Vol Shadow Samples value. The default value is 20.

Disk Based Dmaps
Lets you save a light's depth maps to disk and reuse them during subsequent renders. By saving depth maps to disk, and reusing them later, you can decrease the time it takes to render the scene (see Reuse depth maps). Depth maps are saved in the renderDate/depth directory.

Off
Maya creates new depth maps during rendering. Maya does not read depth maps from disk. Maya does not save depth maps to disk.

Overwrite Existing Dmap(s)
Maya creates new depth maps, and saves them to disk. If depth maps already exist on disk, Maya overwrites them. When you write them to disk, you get two dmaps: One is the first shadow casting surface, the other is the second shadow casting surface.

Reuse Existing Dmap(s)
Maya checks to see if depth maps have previously been saved to disk. If so, Maya uses them instead of creating new depth maps. If not, Maya creates new depth maps and saves them to disk.

Tip: If you are saving depth maps to disk, check the renderDate/depth directory occasionally, and remove any unnecessary depth map files.
 

• (for area lights only) where shadows blur and become lighter as they increase in distance from the object
• to produce shadows from transparent colored surfaces
• to produce soft-edged shadows (though depth maps can also produce good results)