Maya Rendering Lights and Shadows
Troubleshooting Shadows

Jagged or flickering shadow edges
For shadow casting spot lights-Decrease the Cone Angle.

For shadow casting directional lights-Turn on Use Light Position, turn off Use Dmap Auto Focus, and set Dmap Width Focus so all objects that you want to cast shadows do indeed cast shadows for all frames of the animation.

To determine the Dmap Width Focus value, select Panels > Look Through Selected, and zoom the view in or out until all shadow casting objects are visible. Note the width of the view and use this value for Dmap Width Focus.

For all light types-You can do one of the following:

Turn off Use Light Position (for directional lights only), turn on Use Dmap Auto Focus for the light, and turn off Casts Shadows for any objects (especially large objects) in the scene that do not need to cast shadows (they can still receive shadows).
Increase Dmap Filter Size (to the lowest value that produces acceptable results) for the shadow casting light (this will make shadow edges softer).
Increase Dmap Resolution (to the lowest value that produces acceptable results) for the shadow casting light.


Grainy or flickering shadows in illuminated fog
Increase Fog Shadow Samples (to the lowest value that produces acceptable results) for the shadow casting light.


Dark spots or streaks on illuminated surfaces (outside of shadows)
Turn on Use Mid Dist Dmap for the shadow casting light that illuminates the surface.

or

Increase Dmap Bias by a small amount for the shadow casting light that illuminates the surface.



Shadow appears detached from shadow casting surface
Decrease Dmap Bias by a small amount for the shadow casting light.



Grainy or flickering shadow edges (raytraced shadows)
Decrease Light Radius (point lights or spot lights) or Light Angle (directional lights) for the shadow casting light. This will also make shadow edges sharper.

or

Increase Shadow Rays (to the lowest value that produces acceptable results) for the shadow casting light.



Staircase of dark triangles on surface (raytraced shadows)
Increase Curvature Tolerance for the surface.

or

Increase U Divisions Factor and V Divisions Factor for the surface (to the lowest values that produce acceptable results).

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