Depth Bias

Anapplicationcanhelpensurethatcoplanarpolygonsarerenderedproperlybyaddingabiastothez-valuesthatthesystemuseswhenrenderingthesetsofcoplanarpolygons.Toaddaz-biastoasetofpolygons,calltheSetRenderStatemethodjustbeforerenderingthem,settingtheStateparametertoD3DRS_DEPTHBIAS,andthevalueparametertoavaluebetween0-16inclusive.Ahigherz-biasvalueincreasesthelikelihoodthatthepolygonsyourenderwillbevisiblewhendisplayedwithothercoplanarpolygons.

Offset=m*D3DRS_SLOPESCALEDEPTHBIAS+D3DRS_DEPTHBIAS

wheremisthemaximumdepthslopeofthetrianglebeingrendered.

m=max(abs(deltaz/deltax),abs(deltaz/deltay))

TheunitsfortheD3DRS_DEPTHBIASandD3DRS_SLOPESCALEDEPTHBIASrenderstatesdependonwhetherz-bufferingorw-bufferingisenabled.Theapplicationmustprovidesuitablevalues.

Thebiasisnotappliedtoanylineandpointprimitive.However,thisbiasneedstobeappliedtotrianglesdrawninwireframemode.

//RenderStates
D3DRS_SLOPESCALEDEPTHBIAS,//Defaultstozero
D3DRS_DEPTHBIAS,//Defaultstozero

//Caps
D3DPRASTERCAPS_DEPTHBIAS
D3DPRASTERCAPS_SLOPESCALEDEPTHBIAS