Long rendertimes although grid is empty...

[48design]

Hi!

I'm having a scene where at a specific frame my phoenix simulation is starting. Before this frame my simulation grid is empty and the smoke starts to fill up that grid. If I render my scene (VRay) before this frame I'm having about three times slower rendertimes when Phoenix/the grid is visible. If I hide the grid, rendertimes are much better. Does this make sense? Isn't there a "dirty flag" that tells the renderer to ignore Phoenix while the grid is empty?

In the same scene, where I'm emptying an object at a different frame (liquid simulation this time) I'm having the same trouble. Before the simulation begins Phoenix is holding the initial/non moving liquid object. Doesn't it keep this "static mesh" and optimize rendering this way? I managed to fight this issue by converting the liquid to a mesh switching to the Phoenix version at the frame the animation begins but it's not really comfortable.

Best regards
Fabian

[Ivaylo Katev]

there is no "empty" flag because it's supposed that the grid is empty only few frames before the smoke or liquid appears. if you have long sequence that contains an empty grid, you can render it with disabled phoenix rendering until the frame where some activity starts.

[48design]

Hi Ivaylo,

that's what I do but It needs to split up the rendering process. While this may be fine for the smoke/steam it is pretty bad when doing liquid simulations. I wrote a workaround for that above but the converted mesh is not the same as the Phoenix version and you can't use clipping gizmos for example.

Best regards
Fabian

[Svetlin.Nikolov]

Hello, which Phoenix version are you using? Official 2.2, a more recent nightly, or an older official? Also, max or maya?
We do have an optimization for such scenes. What is your resolution?

[48design]

At the moment I'm using one of the latest nightlies but even before VRay 3.x with older Phoenix versions I had the same problems. I'm using 3D Studio Max. I've sent you the scene already today but for other problems regarding VRay, not Phoenix, although this all seems to be related to each other.

edit:
The build number is 24894, every build I tried after this one crashed 3D Studio Max while starting.

[Svetlin.Nikolov]

Whom is the scene sent to?

[48design]

Tsvetan Geshev

[Svetlin.Nikolov]

Roger that, we'll investigate and get back to you with either a fix or better workaround.

[48design]

Thank you!

[Svetlin.Nikolov]

Hello! We could not reproduce the 3-fold slowdown with the scene provided. If you un-check the "Load nearest" option in the input panel of all 3 simulators, Phoenix is not referred at all when rendering during the first 300 frames. As the "load nearest" is only checked on the tomato sauce simulator, unchecking it was the only performance gain we could find, if the simulator is unhidden. Also, you could try to render the liquid simulator in mesh mode to improve render times.

Is there anything more you could tell about the major slowdown? Does it happen only using DR, or you can get it locally as well? If it does occur only in DR, how many machines are involved?

[Svetlin.Nikolov]

Btw, you could improve the rendering speed before the time comes for the tomato simulator. If you uncheck 'load nearest' and use the 'direct index' input mode. You can animate it so that before the simulation the frame can't be found (e.g. use -1), then during the simulation the cache index directly corresponds to the timeline frame, and after the simulation the last cache index is used onward.

[48design]

Hi,

I'm not at this scene at the moment. I will look into that and report. All I remember is that rendertimes where two or three times higher with an empty grid than with the grid hidden...

Best regards
Fabian

[Svetlin.Nikolov]

Oh sure, whenever it's possible for you. Any clues you can find on how we can reproduce the issue will be of help.