# Documentation/Transparency shadow maps

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Regular shadow maps compute a depth map from the point of light. The shadow shading language can be used to check the depth of the point in the same view against the depth stored in the map to figure out if the point is in the shadow or not. Unfortunately, regular shadow maps store only depth. So it is not possible include semi-transparent objects in the shadow. Transparency Shadow Maps (TSM) fix this issue by storing a transparency as a function of depth for each pixel. They allow many semi-transparent objects to cast correct shadows.

To compute a TSM you need to use the "tsm" display driver:

    Display "test.tsm" "tsm" "z"     -    Compute TSM

or

    Display "test.tif" "file" "z"    -    Compute regular shadow map

The usage of the transparency shadow maps is the same as regular shadow maps: thru the shadow shading language call. In the case of a regular shadow map, Pixie will lookup binary in/out of shadow values. In the case of the transparency shadow map, the actual opacity amount at the query value will be returned.

When looking up the shadow map remember to use the following syntax

    color shd = color shadow(...)

to ensure a full color transparency lookup.

Retrieved from "http://www.george-graphics.co.uk/pixiewiki/Documentation/Transparency_shadow_maps"

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