PerspectiveCameras principal point

[classner]

🐛 Bugs / Unexpected behaviors

Hi team!

Someone just reached out to me concerning unexpected behavior of PerspectiveCameras in conjunction with Pulsar. I tracked this back to here

pytorch3d/pytorch3d/renderer/cameras.py

Line 1266 in 1b0584f

principal_point=((0.0, 0.0),),

. The default initialization for PerspectiveCameras uses a principal point of (0., 0.), which, according to the documentation is the xy coordinate of the principal point (and hence places it in the top left corner). Is that intended and shouldn't it be half of image size by default? Could it be that this definition changed during the last year at some point? In any case, the Pulsar unified interface is currently using this value incorrectly in

pytorch3d/pytorch3d/renderer/points/pulsar/unified.py

Line 249 in 1b0584f

principal_point_x = (

and

pytorch3d/pytorch3d/renderer/points/pulsar/unified.py

Line 323 in 1b0584f

principal_point_x = (

. I'm happy to make a PR once clarified how it's intended to work.

[gkioxari]

@classner
This is NDC coordinates, so (0,0) is the center of the image.