The OptiX intersection program for curves uses "optixGetObjectRayDirection"
to get the ray direction in object space (which was inverse transformed
with the current transformation matrix). OptiX does no additional operations
on it, so if there is a scaling transform, the direction is not normalized.
But the curve intersection routine expects that. In addition, the distances
used in "optixGetRayTmax()" and "optixReportIntersection()" are in world
space, so need to adjust them accordingly.
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