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Consider a vertical cylinder with a camera orbiting it in a horizontal plane. At any point in time, the camera gets a good view of the part of the cylinder facing it, but the portions seen edge on can not be seen well, as the texture is fore-shortened with the pixels crunched together. As the camera orbits, the portions that can been seen well, and not seen well, change continuously.
Although the tilt weighting reduces the effect of edge-on triangles, we provide an additional hard-and-fast control.
To ensure that texture extraction proceeds on the portions that can be accurately extracted, and ignores the portions that can not, there is a Tilt control.
With the tilt control at zero, all grazing angles are considered. At one, extraction proceeds only on the portions where they precisely face the camera, with intermediate cutoff angles at values in between. (Multiply by 90 to get the relevant angle.)
The tilt angle check is performed on a facet-by-facet basis, so meshes where this calculation is necessary should have adequate segmentation. If there are only 12 facets
around, for example, then there will only be 3 facets between straight-on and edge-on, roughly 30 degrees at a time will be turned off or on. A segment count of 48 would be a better choice.
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