Hello,

I am struggling with a pyro steup. I got a river delta like shape of a flip sim that represents lava. I want to use the flip particles as a source for a pyro sim.

For faster art direction, I deleted most points except a small area. When I volume rasterize and simulate this small area I am getting the desired results.

BUT: If I use all the source particles, the volume rasterize and the sim looks different very different from the little patch as an isolated volume. I have compared the density values and the grid size of the volume rasterized particles using a volumeslice and found that they look identic there. But seen as a regular volume in viewport they look vastly different.

Then I thought, "well maybe it's just the viewport that renders different" and played with the display parameters. Then I realized though, that even the sim behaves vastly different. It is a sparse solver in a dop network by the way. But if the volumeslice shows identic data, then it's maybe some interpretation by the viewport and the pyro network?

What am I doing wrong? And how do other people approach the issue of a pyrosim that covers a rather wide area but doesnt need much detail. I could split the sim in little patches and I guess the result would be fine but it really bugs me that I don't understand what's going on. I felt like I finally understand volume stuff reasonably well.

I'm on houdini 19.

I greatly appreciate your help!

Too make my question more clear, I prepared and example file and attached it.

There's a volume rasterized out of a long line of noisy particles and then a volume created just out of the center piece.
As a volume in viewport they look different. But as seen throgh a volumeslice they look the same. Why is this so?

Again, thanks a lot.
Oliver

Okay, further testing has been done.
Actually, only the viewport looks different (even after the pyro solver) but when rendered, they look the same. So the data is indeed the same. That kinda answers all former questions I guess...

But now my (hopyfully)final question for today:

Can I tell the houdini viewport to render both volumes more similar to each other?

O_Speiser
Can I tell the houdini viewport to render both volumes more similar to each other?

Do the volumes have the same dimensions? In the viewport a volume is a 3d texture; the number of voxels used in the viewport is clamped to the number specified in each dimension regardless of size. The default is 128^3 or 256^3 depending on if you reset your desktop or not.

They have different dimensions. The one is bigger and the other one is a little pice cut out of it.
I have gathered that size doesn't matter, as when resized the displayed resolution does not change.
The deciding factor seems to be the total resolution or number of voxels. The more voxels I've got, the more blurred details look in the viewport.
I played around with the values for 3d textures but they didnt change anything.
I guess it's not a big deal in general but a little unfortunate in this particular setup.

I'd look again at your 3d texture limit resolution setting, it really sounds like that is the issue. You might have to change to another frame in the timeline to see the effect after changing the values.

Tanto
I'd look again at your 3d texture limit resolution setting, it really sounds like that is the issue. You might have to change to another frame in the timeline to see the effect after changing the values.

Thank you for the answer,

you are correct. I tested the setting but the problem was that I didn't look at another frame so it never updated the viewport render. Somtimes these silly little problems can cause more headache than necessary in the world of CG.

Thanks a lot!