LOD system does not recognize when camera enters AABB (solution provided)

[roalyr]

Tested versions

4.x as of 2d0ee20

System information

Any platform

Issue description

In the LOD system:

// Get the LOD support points on the mesh AABB.
Vector3 lod_support_min = inst->transformed_aabb.get_support(p_render_data->scene_data->cam_transform.basis.get_column(Vector3::AXIS_Z));
Vector3 lod_support_max = inst->transformed_aabb.get_support(-p_render_data->scene_data->cam_transform.basis.get_column(Vector3::AXIS_Z));

// Get the distances to those points on the AABB from the camera origin.
float distance_min = (float)p_render_data->scene_data->cam_transform.origin.distance_to(lod_support_min);
float distance_max = (float)p_render_data->scene_data->cam_transform.origin.distance_to(lod_support_max);

Both distances are always positive values, so the condition that checks if camera is inside AABB:

if (distance_min * distance_max < 0.0) {
	//crossing plane
	distance = 0.0;
}

Never triggers.

Video: https://www.youtube.com/watch?v=j_rp_k5rDPA

Solution

To fix the issue - supplement distance_min with a sign, for example: roalyr@afbdb54
Video: https://www.youtube.com/watch?v=LF21eYlb44Y

I am not opening a PR because I am not sure if this approach is the best.

Steps to reproduce

Set LOD bias to a really low value (0.1) and move camera inside AABB of a mesh, rotate the view.

Minimal reproduction project (MRP)

Irrelevant

[roalyr]

Also

} else if (distance_max <= 0.0) {
    distance = -distance_max;
}

needs to be addressed in the same fashion, because distance_max doesn't get negative either.

[roalyr]

In fact, it is questionable why distance_max is used at all. Why not origin?

[clayjohn]

Fixed by #79590 or #92232