[Enhance] Replace BEV IoU with 3D IoU

[filaPro]

Motivation

BEV IoU is not needed now in open-mmlab projects after replacing iou3d ops with box_iou_rotated and nms ops. So now we can support fair 3d IoU instead of BEV IoU. This was discussed with @ZwwWayne and @Tai-Wang as a part of work on FCAF3D in mmdetection3d.

Modification

Modify python and cuda functions in mmcv.ops.iou3d to accept not (x1, y1, x2, y2, heading) but (x, y, z, dx, dy, dz, heading) boxes.

BC-breaking (Optional)

It breaks all 3 functions in mmcv.ops.iou3d.

Use cases (Optional)

Fair 3D IoU is a must have function for indoor 3D object detection.

May be @grimoire to have a look on cuda part.

[grimoire]

LGTM

[zhouzaida]

Please @Tai-Wang have a look

[Tai-Wang]

As current mmdetection3d master is using bev iou ops. Have you PR a fix there?

@grimoire A related PR in mmdet3d has been merged into the dev branch and will be merged into master in the next release soon. I have the same concern with you and would prefer to avoiding some potential issues with more safe modifications.

[Tai-Wang]

Hi @filaPro , great work! The only concern is that does the current modification remove the original ops directly? If other users use related bev ops in their projects, it will trigger errors? If yes, I think it would be better to keep original ones for several mmcv versions and just throw deprecated warnings to avoid these potential issues.

Besides, if possible, I recommend we can support the bev ops based on these more comprehensive 3D ops. (I think the deprecated bev ops should be just special cases of these 3D ops?)

[filaPro]

Hi @Tai-Wang,

Deprecated functions can be replaced with either box_iou_rotated + nms or novel iou3d ops. We chose the first option in mmdetection3d. But yes, we can probably support the second options here with DeprecationWarning.

[filaPro]

So, I reverted 3 original python functions with minimal changes in code, but with DeprecationWarning. Also, I checked that original 3 tests are also passing now.

[filaPro]

Hi @ZwwWayne ,

Sorry for late reply. I've update the deprecated bev iou/nms with current mmcv ops (without 3d nms/iou). Also checked that old tests are still passed.