Fixed Hollow Block Collides and Flies Away When Dropped

[Richal13Yu]

I encountered an issue while using Genesis to simulate a fixed hollow block dropped onto a column. When I attach the hollow block to the column(fixed=True), everything works as expected. However, if I drop the hollow block from a higher position:

• It collides with the column.
• Instead of dropping to the bottom of the column as expected, it flies away unexpectedly.

[Richal13Yu]

hi, I saw the issue==444, and tried it in my code, but it still fails to convert my nonconvex item.

here is my code.

board_surface = gs.surfaces.Glass(color=(0.8, 1.0, 0.0),vis_mode='collision')
block_surface = gs.surfaces.Plastic(color=(1.0, 0.0,0.8),vis_mode='collision')

coacd_options=gs.options.CoacdOptions(threshold=0.1, preprocess_resolution=10)

pos_block=np.array([0.033, 0.05075, 0.08])
pos_block[0]-=0.077
pos_block[1]-=0.0515
block = scene.add_entity(

gs.morphs.Mesh(file='stl/block.stl',
               pos=pos_block,
               fixed = True,
               decompose_nonconvex = 1,
               coacd_options = coacd_options,
               ),
surface = block_surface

)
board = scene.add_entity(
gs.morphs.Mesh(file='stl/board.stl',
fixed = True,
pos=[0,0,0.02],
decompose_nonconvex=1,
coacd_options=coacd_options,
),
surface = board_surface
)

[zhouxian]

Do you have a video?

[Richal13Yu]

Do you have a video?

Sure! The block shoud fall in the boards' collomn, but they maybe loaded wrong

nocoacd_options.webm

coacd_options.webm

[wangyian-me]

First of all, set preprocess_resolution=100 to better preserve the original geometry.
Secondly, the coacd is not guaranteed to fully preserve geometry even when preprocess_resolution=100, you might want to use the sdf based contact in this case. Adjusting the sdf resolution might help.