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Been meaning to post this for months, finally got around to it.
This is a very curious bug; easy enough to diagnose the cause and workaround, but its behaviour is very odd.
This circular rug is an approx 2000mm diameter, 10mm thick cylinder, the thin edges of which are beveled and smoothed.
This was done simply by copying one of the perimeter circles halfway down the side edges, then scaling that circle up a little
so the edges bulge out a little. It has a diffuse bitmap and a similar bump map applied using identical UV
coordinates. First image is SU output for reference.
The bug is that when heavy smoothing is applied (over 70° to make the edges disappear in SU) the bump map goes crazy,
see VfSU rendered 2nd and 3rd images. It's not clear at this resolution, but at full screen res the incorrectly rendered area
shows multiple overlapping identical bump maps, but at completely random scales and even distorted. The even stranger thing is
that it is viewport dependant- note that when the camera has moved in the 3rd image the incorrectly rendered bump area moves
with it, but not in any logical manner as far I can discern. So the smoothing appears to cause the bump mapping to no longer
be properly fixed to the geometry, but has somehow developed a relationship with the camera position.
The workaround is simply to remove or reduce the smoothing on this object (70° is very high anyway), but it apparently has
something to do with the circular form of the rug as I haven't seen this behaviour on other SU smoothed geometry. Final image
shows correct VfSU render when SU smoothing is removed from the geometry.
This is a very curious bug; easy enough to diagnose the cause and workaround, but its behaviour is very odd.
This circular rug is an approx 2000mm diameter, 10mm thick cylinder, the thin edges of which are beveled and smoothed.
This was done simply by copying one of the perimeter circles halfway down the side edges, then scaling that circle up a little
so the edges bulge out a little. It has a diffuse bitmap and a similar bump map applied using identical UV
coordinates. First image is SU output for reference.
The bug is that when heavy smoothing is applied (over 70° to make the edges disappear in SU) the bump map goes crazy,
see VfSU rendered 2nd and 3rd images. It's not clear at this resolution, but at full screen res the incorrectly rendered area
shows multiple overlapping identical bump maps, but at completely random scales and even distorted. The even stranger thing is
that it is viewport dependant- note that when the camera has moved in the 3rd image the incorrectly rendered bump area moves
with it, but not in any logical manner as far I can discern. So the smoothing appears to cause the bump mapping to no longer
be properly fixed to the geometry, but has somehow developed a relationship with the camera position.
The workaround is simply to remove or reduce the smoothing on this object (70° is very high anyway), but it apparently has
something to do with the circular form of the rug as I haven't seen this behaviour on other SU smoothed geometry. Final image
shows correct VfSU render when SU smoothing is removed from the geometry.
