[GodotPhysics] Fix raycasts don't reliably collide with HeightMapShape3D

[kevinkuo52]

• Fixes [GodotPhysics] Raycasts don't reliably collide with HeightMapShape3D #68238

Tested this fix on both of the MRPs shared and it seems to work
heightmap_raycast_repro.zip
raycastHeightmapBug.zip

If there's cleaner way to fix this, or if I missed something, let me know thanks

Details:
Raycast with issue fall under this case where ray is long so it does query on higher level grid first

godot/modules/godot_physics_3d/godot_shape_3d.cpp

Line 1998 in f7c567e

return _intersect_grid_segment(_heightmap_chunk_cull_segment, bounds_from, bounds_to, bounds_grid_width, bounds_grid_depth, bounds_offset, r_point, r_normal);

And issue looks to be in the loop here, it exit before it got to the chunk where the ray actually intersect

godot/modules/godot_physics_3d/godot_shape_3d.cpp

Lines 1940 to 1941 in f7c567e

	if ((x < 0) || (z < 0) || (x >= p_width - 1) || (z >= p_depth - 1)) {
	break;

p_width and p_depth is the chunk's width and depth for this flow
using heightmap_raycast_repro.zip as example
p_width = ceil( width/chunk size) = ceil( (21/16) = 2
p_depth = ceil(depth/chunk size) = ceil( (21/16) = 2
x = 1 or z = 1 should still be valid chunk, but it will exit here.

But can't directly change that line to if ((x < 0) || (z < 0) || (x >= p_width) || (z >= p_depth))
because _intersect_grid_segment() is used by cell level too, where in _heightmap_cell_cull_segment:

godot/modules/godot_physics_3d/godot_shape_3d.cpp

Lines 1754 to 1755 in f7c567e

	p_params.heightmap->_get_point(p_state.x + 1, p_state.z, p_params.face->vertex[1]);
	p_params.heightmap->_get_point(p_state.x, p_state.z + 1, p_params.face->vertex[2]);

it performs get point on the triangle with p_state.x + 1, p_state.z + 1 etc so it will hit out of range on the edge cell if we change that line

This PR passes bounds_grid_width + 1, bounds_grid_depth + 1 to _intersect_grid_segment() with a comment to explain this,
if there's cleaner way let me know 😅

[rburing]

Looks good, thanks a lot for your contribution!

[Repiteo]

Thanks!