oCOSMO Cosmo 3DTM Manual

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Back Patch Culling

157

Face normals are used by default with the following primitive types:

• csPolySet

• csQuadSet

• csTriFanSet

• csTriSet

• csTriStripSet

If normals are not provided for a csGeoSet and the primitive normal mode is enabled,

the csGeoSet is never back patch culled.

Using Back Patch Culling

There are two steps you take to implement back patch culling:

• Enable back patch culling.

• Build back patch culling data.

Enabling Back Patch Culling

You enable back patch culling by setting csDrawAction::setBPCullMode() with one of

the following arguments:

• NONE—Disables back patch culling.

• DRAW_FRONT_FACING—Culls all primitives wholly on the back side of a

geometry.

• DRAW_BACK_FACING—Culls all primitives wholly on the front side of a

geometry.

csDrawAction::getBPCullMode() returns the back patch culling mode.

Once back patch culling is set, it is carried out whenever an apply() method is invoked

with a csDrawAction.