Hi Guys;

I am trying to figure out a few kinks on a rig I am working.

I have a rig in Houdini with pyro that works just fine with colliders etc in Houdini and in Maya through Maya Engine.
Houdini 15.5 and 16 and Maya 2015

The Problem is when I cache out maya fluids cache and load back in the cache, i cannot see the velocity field. I will be also needing custom fields like rest, so Maya fluids has color field that can be cached out, so regarding these I have a few questions.

My other problem is the scale, by default fluid container size is set to 1 and its transform is scaled instead it also get transforms, this becomes a problem for some of our tools, voxel position is wrong in objectspace. Was this an intended design ?

Before my output node,
Do I have to rename vel to velocity, or engine fluid will do the conversion?
What workflow would you suggest to pass through the rest field, i currently rename it to color as maya fluids have color caching, so i was thinking to replace that since thats a vector too.


thanks

tricecold
The Problem is when I cache out maya fluids cache and load back in the cache, i cannot see the velocity field.

Is the velocity field being outputted in the display SOP? The Pyro shelf normally creates a “pyro_import” object that contains two SOPs. One has the display flag set, and the other one has the render flag set. The displayed SOP is the one that'll be outputted to Maya. But the displayed SOP is used for visualization in
Houdini, and doesn't contain the velocity field. In that case, you probably want to set the display flag on the rendered SOP.

tricecold
My other problem is the scale, by default fluid container size is set to 1 and its transform is scaled instead it also get transforms, this becomes a problem for some of our tools, voxel position is wrong in objectspace. Was this an intended design ?

This was the intended design at the time, but I would also prefer it to have the proper object size. I tried to change this a long while back, but I ran into some issues. Let me take a look at it again, and see if this can be changed now.

tricecold
Before my output node,
Do I have to rename vel to velocity, or engine fluid will do the conversion?

The Maya plugin should handle the conversion. Maybe the displayed SOP isn't outputting the velocity field?

tricecold
What workflow would you suggest to pass through the rest field, i currently rename it to color as maya fluids have color caching, so i was thinking to replace that since thats a vector too.

Unfortunately, your options are very limited, since Maya's fluid shape node only has a fixed set of fields that can exists. Like you said, the best bet is probably to store the Houdini field in one of the available fluid shape field. You can do this in your asset by renaming your volume to Cd..

Thanks for the replies, no I am not using out of the shelf nodes for the rig.


I tought some how for each in import fields was breaking the vels, so i fetched each field seperately with dopimport1, display flag was set properly on where the data was.

The thing is, tools has to be used in Maya, and rerendered in Houdni, because we want to use volume procedural and i need the rest field to stick the noise.

I would be very happy to get back BGEOs also, but a filecache node doesnt work, because it cannot tell maya to change frame, unless there is a way I dont know, I would be happy to hear that.

I checked the mcx cache from Maya and it outputs color channel, which I already tried renaming rest from Houdini, but it overrites the values. I wonder if the connection editor would allow me to reqire these manually.

I will continue the research tomorrow.

In terms of scale, i will make a little script to reverse the values from scale to size etc, which seemed to work but, I guess ideally we would like to keep the original values.

Thanks
Tim

tricecold
I tought some how for each in import fields was breaking the vels, so i fetched each field seperately with dopimport1, display flag was set properly on where the data was.

On Maya's fluid shape node, if you enable “Display -> Velocity Draw”, are you able to see the velocities drawn in the viewport?

tricecold
I would be very happy to get back BGEOs also, but a filecache node doesnt work, because it cannot tell maya to change frame, unless there is a way I dont know, I would be happy to hear that.

String parameters are evaluated as Houdini expressions. So you can use variables like $F and $F4 in file paths to allow changing frames.

tricecold
I checked the mcx cache from Maya and it outputs color channel, which I already tried renaming rest from Houdini, but it overrites the values. I wonder if the connection editor would allow me to reqire these manually.

Does the color appear in the fluid shape that the asset created in Maya?
After caching, when you import the cache, you also need to make sure “Color Method” on the fluid shape node is set to “Dynamic Grid”.