Vertex Animation Texture - RBD - Houdini to Unreal - Checklist

[WLVL]

Hey Houdinians,

I have made a check list gathering infos from the webinars/tuts done by the great Houdini GameDev Toolset Team.

Please let me know if something is missing or wrong, I hope this is helpful for some of you.

 

Rigid Body Dynamics Vertex Animation Texture - RBD VAT

optimal for high # of pieces.

alternatives (bones, straight fbx)

 

in HOUDINI:

 

1-

rbd material fracture SOP

proxy to rbd bullet sim

 

2A-

dopimportSOP(fetch geometry from DOP network)

OUT to VAT ROP

 

 

2B- 

this step if you need to add edge/interior details or manipulate geo

static highres full geo

add uvs (autouvSOP)

limit number of poly, polyreduceSOP (precision errors in ENGINE if npoints/nprims is too high)

hou material: shop_materialpath prim attribute (unreal will replicate houdini's)

or assign unreal mat: unreal_material prim attr (in UNREAL/content menu//right click on material/copy ref path)

 

pack fragments (assemble SOP)

add rest point attribute (VAT ROP needs rest)

 

dopimportSOP (create point to represent objects) 

 

use transform pieces to apply motion to high res geo

copy template attributes ON (VAT ROP needs orient + pivot)

OUT to VAT TOP

 

 

3-

VAT ROP

method to RBD

will export a mesh fbx, a pos texture, a rotation texture.

textures size min will be: [ n of packed prim * n of frames ]

 

 

in UNREAL:

 

import VAT passes (pos.exr, rot.exr, mesh.fbx)

 

pos/rot texture:

details/compression_setting/vertex displacement (HDR default not needed, exr is normalized)

details/texture/filter/nearest

 

mesh:

details/import_setting/mesh/vertex_color_import_option/Replace (pivots are stored here)

details/import_setting/mesh/Remove Degenerates/OFF

details/LOD0/build_setting/Remove Degenerates/OFF

details/LOD0/build_setting/full precision uv/ON 

 

create material

details/material/tangent space normal OFF (we write data in world space)

details/material/num_custom_UVs , set to 3.

copy/paste material code from houdini VAT ROP/Rigid Vertex Animation UE Code

connect outputs (base cd, normals, trans offset)

connect (uv1,2, ...) (pass data from vertex shader to texture shader)

 

 

create material instance from material

copy bbox max, bbox min, bbox max1, bbox min1, n frames, from houdini VAT ROP

set playback speed to 1 (it's a multiplier )  (framerate fps / total number of frame animation)

assign pos and rot texture to translation and rotation textures

assign material instance to rbd mesh.fbx

 

---

 

 

tested on Houdini 17.0.416, Game Dev Toolset 1.96

rbd_VAT_workflow_v01.hiplc

Edited December 20, 2018 by WLVL
correction

[misterbil]

Hello

thanks a lot for posting that!

I was having issue with pivot point not working, so I took your file and tried it without changing anything.

and I have the same issue.

in houdini it looks great:

but in UE4:

 

Any Idea?

 

[WLVL]

Glad you found this useful.
Double check that you are copying bbox max, bbox min, bbox max1, bbox min1, values correctly to the material instance parameters in unreal

[misterbil]

Yes, super useful !

I did double check (I found another of your post about it ).

 

I included the textures, geometry and Material.  I got out of houdini, if you have a chance to test them and see if you get the same result.

I'm on houdini 17.0.416

and unreal 4.21.2

 

PS: I also tested a scene with their gamedev RBD director, solver and what not but have the same results (weird pivot offset), that's why I think it's something in my UE4 set up.

thanks a million.

 

test_rot.exr

test_pos.exr

test_geo.fbx

M_vat_Test.txt

[bobcober]

When importing into UE - make sure that Vertex Paint is set to Replace.  for rbd the vertex colors are used to store the packed fragment offset - this is why the rotations are jacked

[josich]

Thanks bobcober I was having the same problem as misterbil and I wasn't able to find a solution.

Edited November 20, 2019 by josich