OptiX Prime matrix dimensions

Perhaps I’ve missed something basic, but I just can’t seem to reconcile the dimensions of the affine transform matrices used in OptiX Prime with the documentation/my expectations.

OptiX Prime provides a buffer format RTP_BUFFER_FORMAT_TRANSFORM_FLOAT4x3, ostensibly for 4x3 matrices, i.e., those of four rows and three columns. But the documentation clearly states that the last row is always assumed to be [0, 0, 0, 1], which has four columns. And in fact, examples such as primeInstancing.cpp clearly show 3x4 matrices (which are nevertheless consistently referred to as 4x3 matrices!)

What’s going on here? Is this just bad usage by the SDK, or is there something more subtle I have missed?

Yes, the enum is named incorrectly and should have been RTP_BUFFER_FORMAT_TRANSFORM_FLOAT3x4.
This is already tracked in an internal bug report and will hopefully be resolved in the near future.
Sorry for the confusion.