VAT 3 slerp with object level transforms

   1260   6   0
User Avatar
Member
43 posts
Joined: May 2013
Offline
I am having a problem with rotations in VAT 3.0. It seems like object level transforms are not handled correctly. I have geometry coming in from Unreal with rotations that are getting screwed up, I think by the SLERP nodes down in the VAT node. I think rotations are getting messed up at this node:


/obj/ropnet1/vertex_animation_textures1/objects/TEXTURE/update_rest_intrinsic_xform


I have a complicated setup that works perfectly with VAT 2.1. I'd like to be able to use the interpolation in VAT 3.0 for imporoved performance, but I need to get the rotations working correctly.


I output the fbx and textures from the attached Houdini file and dragged them into UE, and the pieces are not rotated correctly. Please see attached pictures.


Oddly, my production example seems to get screwed up at the preprocess_slerp_edge_case node.


I hope there's a simple way to bring the geo from Unreal and bury the xforms in a way that the VAT tool is happy with. Any help appreciatred.
Edited by johnLIC - Sept. 7, 2021 15:12:38

Attachments:
slerp_UE.png (1.7 MB)
slerp_Houdini.png (487.5 KB)
slerp_problem_example.hip (3.4 MB)

User Avatar
Staff
82 posts
Joined: Feb. 2021
Offline
johnLIC
I am having a problem with rotations in VAT 3.0. It seems like object level transforms are not handled correctly. I have geometry coming in from Unreal with rotations that are getting screwed up, I think by the SLERP nodes down in the VAT node. I think rotations are getting messed up at this node:


/obj/ropnet1/vertex_animation_textures1/objects/TEXTURE/update_rest_intrinsic_xform


I have a complicated setup that works perfectly with VAT 2.1. I'd like to be able to use the interpolation in VAT 3.0 for imporoved performance, but I need to get the rotations working correctly.


I output the fbx and textures from the attached Houdini file and dragged them into UE, and the pieces are not rotated correctly. Please see attached pictures.


Oddly, my production example seems to get screwed up at the preprocess_slerp_edge_case node.


I hope there's a simple way to bring the geo from Unreal and bury the xforms in a way that the VAT tool is happy with. Any help appreciatred.

Yeah I am aware of this issue. It happens when there are some non-standard transforms in the input. It's on my to-do list. Will look into it.
Mai Ao
Technical Artist at SideFXLabs
twitter.com/aomai01
User Avatar
Member
43 posts
Joined: May 2013
Offline
Can you please let me know when there's a fix? ...post in this thread or something? thx
User Avatar
Staff
82 posts
Joined: Feb. 2021
Offline
johnLIC
Can you please let me know when there's a fix? ...post in this thread or something? thx

Yeah I will post it here when it's fixed.

update_rest_intrinsic_xform is doing something a bit unintended I think, but it doesn't actually mess up anything in the output. More of a benign bug. Before I push the fix (in a week or so), you can avoid running into this issue by making sure to pack your RBD pieces before the solver and not add any rotation between pack and the solver.

When you import geometry from Unreal, you can use Object Merge node and set Transform to "Into This Object". Always make sure the Unreal geos are properly transformed into Houdini's space (including unit conversion), before doing any fracturing, packing, and simulation. That generally avoids strange transform issues. If you still have issues and you obviously can't share production assets on the forum, please feel free to email sidefx support directly. Describe your issue to them and mention that the ticket should be assigned to me.
Mai Ao
Technical Artist at SideFXLabs
twitter.com/aomai01
User Avatar
Member
43 posts
Joined: May 2013
Offline
Any word on the fix for this?
User Avatar
Staff
82 posts
Joined: Feb. 2021
Offline
johnLIC
Any word on the fix for this?

Fix for this is coming in November, along with a few other major improvements.
Mai Ao
Technical Artist at SideFXLabs
twitter.com/aomai01
User Avatar
Member
43 posts
Joined: May 2013
Offline
Did the SLERP transforms get ironed out? If not, are VAT 2.0 and VAT 3.0 both available in Houdini 19? We're using H18.5 and Unreal 4.27 now, and looking to install the latest Houdini Engine plugin, which looks like it's intended to be used with H19. Is it safe to upgrade to H19 and the latest Houdini Engine?
  • Quick Links