[Sidefx-houdini-list] Alembic from Houdini to Maya - transfer "N" and "v" ?

Fabricio Chamon fabricio.chamon at gmail.com
Mon Feb 26 13:52:34 EST 2018


"...by using the *attribute rename* node."

I meant *attribute create*

2018-02-26 14:48 GMT-03:00 Fabricio Chamon <fabricio.chamon at gmail.com>:

> Hey Nikita, thanks for your replies and sorry for the delay.
>
> I continue on my quest of exchanging assets back and forth between houdini
> and maya (vray). While mb is still something I'd have to further
> investigate, either by working on your suggestions or by using vray
> proxies, I'm making progress on other stuff like normals and multiple UV
> sets.
>
> For multi uv sets, I've found out that the houdini alembic importer maps
> maya's current uv set (as found in the mesh controls section) into the
> common "uv" attribute, then wipes out all data from the properly named uv
> attribute. So let's say your imported mesh has 3 uvs:
>
> - uv1
> - uv2
> - uv3
>
> and your current uv set in maya is "uv2". Then you'll end up having:
>
> - uv   (with data of uv2)
> - uv1 (with correct data)
> - uv2 (with no data)
> - uv3 (with correct data)
>
> I tought I'd share this, as someone might need something similar in the
> future. It took me some time to figure out, and I don't know yet how much
> of this is by design or if there is something going on with assets inside
> my production environment.
>
> Other than that I had to make sure all uv attributes are qualified as
> Texture Coordinates, by using the attribute rename node. Now the alembic
> output driver writes all data nicely, and I can read back in maya.
>
> Anyways, I'll keep posting stuff like this, because this kind of
> information is somewhat scarce over the internet.
>
> cheers
>
>
>
> 2018-02-21 3:53 GMT-03:00 Nikita Musatov <not.a.whale at gmail.com>:
>
>> By the way, you can solve the problem with motion blur differently. You
>> can
>> export Alembic with 2 motion sample and emulate moving by velocity. For it
>> before rop alembic output node put TimeShift with expression "floor($FF)"
>> after that add PointAttribute node with expression:
>> float tm = @Frame - floor(@Frame);
>> @P = lerp(@P, at P+@v*@TimeInc,tm);
>> After that look what happens between frames.
>> But this solution works fine if you render motion blur with option start
>> frame (not center of frame) motion blur. For example: Start 0, end 0.3. I
>> think you can rewrite expression that it will work for center of frame
>> motion. But I haven't tried it and don't be sure that will work correctly.
>> I hope it helps you.
>>
>> ср, 21 февр. 2018 г. в 9:34, Nikita Musatov <not.a.whale at gmail.com>:
>>
>> > Hello Fabricio. You can read about velocity on the solidangle page.
>> There
>> > are use Soup plugin for remesh geometry.
>> >
>> > https://support.solidangle.com/display/AFMUG/Motion+Vector+
>> Source?desktop=true&macroName=center
>> > I hope it help for you.
>> >
>> >
>> > On Wed, Feb 21, 2018, 08:38 Fabricio Chamon <fabricio.chamon at gmail.com>
>> > wrote:
>> >
>> >> Hey everyone, as the title says.
>> >>
>> >> I have been trying for the last days...no lucky. there might be some
>> >> gotchas along the way.
>> >>
>> >> May somebody elaborate on what is the consistent way to transfer
>> normals
>> >> and velocities from houdini to maya via alembic **for constant AND
>> >> changing
>> >> topology** ?
>> >>
>> >> I've tried to promote N to various contexts, changing "v" to various
>> names
>> >> (v, vel, velocity) and types (vec3flt, 4flt).
>> >>
>> >> I was not able to get MB working and neither normals (viewport looks
>> >> terrible, altough it kind of renders correclty).
>> >>
>> >> here are some images to illustrate:
>> >>
>> >> maya viewport normals
>> >> <https://www.dropbox.com/s/eyq4igpod72xxd1/tower_viewport.jpg?dl=0> /
>> how
>> >> they look inside houdini
>> >> <https://www.dropbox.com/s/8xtqcd0te03rc96/tower_viewport_hou.jpg?dl=0
>> >
>> >> / render
>> >> comparision in maya
>> >> <https://www.dropbox.com/s/rpe75bakwnuwugr/tower_render.jpg?dl=0>
>> >>
>> >> as for the MB, could not get it to work with any settings. (btw using
>> >> redshift, with deformation blur turned on)
>> >>
>> >> any help is much appreciated!
>> >>
>> >> thanks guys
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>> >>
>> >
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