Hi guys,

I was just testing the new games tools - vertex animation textures rop in particular - I have followed the various examples of how to create and export a very simple cloth sim to unreal. (soft body method)

It creates a correct FBX and a normal map BUT regardless of adding/changing UV's or normals and resetting/opening my scene - the position map (what is most important) doesn't produce a correct position map. I keep getting 8kb ish empty exr's whilst the fbx and normal maps seem correct. I don't appear to be doing anything wrong as far as I know and have tried strange things such as re-ordering nodes etc. (and exporting the normal in the alpha with the position which creates again a correct normal but no info with RGB for position)

Any help would be great (I do perhaps think it could be the version of the tool I'm using perhaps needs updating as I haven't found anyone else online with this issue) or I'm doing something very basic and obvious wrong that I cant see but hopefully not

Please find my hipfile attatched, and the position map exr it is producing

(Houdini version; 16.0736)

Update; Just tried RBD also which works fine and produces a correct position map but the FBX is produces is broken according to unreal - sooo perhaps I need to update the HDA?

Additional info; on rendering to vertex animation sheet using the pigs head as my RBD I get these numbers come up within the Houdini console; (not sure their relevance / meaning but thought maybe of use)

-358.697998047
394.937225342
-358.697998047
394.937225342
-358.697998047
394.937225342
-358.697998047
394.937225342

- Now my RBD Pig scene is exporting position and rotation data correctly from the vertex animation rop but I'm having to manually export the FBX as it doesn't export correctly within the rop for some reason - file is below

I have updated to the latest GitHub release of games tools as far as I am aware of, and still no luck

RBD - FBX exporter seems to be broken (but I work around that manually) - my results in unreal are very broken with the base code shader given for unreal all plugged in correctly as far as I know

Soft body - Still no luck producing a position map - normal and fbx fine however


- Yet to try other methods

Another update - tried using sprite sheets today, but the cameras assigned to create the position map give out errors due to the bounding box function within the camera not working for some reason - I think this is possibly the general error in the other options too (RBD/SOFT/FLUID)

I have tried manually deleting this expression and setting the camera width manually but still errors - (zero resolution for camera - with and without the default expression which points to a bounding box) - however if I manually scrub through with the default expression applied I can see the camera width change so why it errors on batch I don't know as it seems to happily render individual frames if I go into the vertex animation textures node and select the position mantra node and render.

SO I have now got the soft method working by turning normalize data off in the main vertex animation output node - which gives me a working position map

So a small update;

Soft Body for cloth etc. - all working well (theirs a guy on the odforce forum saying he also used the soft body method for a small fluid simulation which worked with some tweaking)

Sprites - all working (need to turn two sided on in the UE4 shader for visibility - but possibly a normal issue so flipping normal in Houdini before export may work too)

RBD - Working but not properly strange rotation interpolations etc (but possibly a small error on my side may fix this or the rotation calculations within the shader may need some tweaks?)

Fluid - Sometimes works kind of (movement is roughly their but horrendous holes and glitching throughout the mesh - as I was writing this tried to export again and this time it doesn't work at all inside UE4 which is odd)

(PS; I have tried various settings and iterations for these methods not just erroring and not making a second attempt - but if anyone notices me making silly or simple mistakes or has solutions please let me know! )

Hi Chris,

I'm testing this functionality myself. I'm wondering if your issues with the Fluid output is the UV precision setting? There's a parameter “Use Full UV Precision” that needs to be turned on.

More info here: https://realtimevfx.com/t/vertex-animation-output-from-houdini/1562/17 [realtimevfx.com]

My issue right now is that copypasting the shader code out of Houdini 16.5 into Unreal 4.18 gives me the shader nodes, but with no interconnections. I'm gonig to try the github version to see if that changes things. I was hoping that the latest would be in 16.5 release.