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Francis Bievre avatar image
Francis Bievre asked ·

Houdini Engine and C4DtoA : exporting time increases with each frame

Hello guys,


I made a houdini simulation of a whale jumping out of the ocean, then imported it to C4D to integrate it in my shot and render with Arnold.

I launched the render yesterday evening, the first frame took around 3mn30 to render, with approx 2mn30 of exporting the sim into Arnold and 1mn of rendering.
I come back this morning and I see that with each frame the render time increases with up to 25mn exporting time !

When I render in the IPR, even the frame 100 takes approx 3mn to render in 1080p.

Would you know what is causing that and how to avoid it ?

Thank you.

Francis

houdini
exporting-times.png (145.6 KiB)
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Peter Horvath avatar image
Peter Horvath answered ·

The problem is caused by the motion blur and hair. Hair is an iterative simulation which means that the current frame is calculated from the state of the previous frame. With center frame motion blur we move backwards on the timeline, so all prior frames have to be recalculated, which becomes slow because of the data in the Houdini Engine.

Actually resimulation should not be necessary in this particular scene because the hair simulation is cached. I have to think of a proper solution, either allow the user to control the behavior or adding some fancy logic to find out when the resimulation is really necessary.

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Francis Bievre avatar image
Francis Bievre answered ·

Ok I'm uploading a 10 gigas file with 4 frames, but I'm not sure it will work as I don't understand how the houdini engine locates its assets :p

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Peter Horvath answered ·

What about a lower quality sim or just a couple of frames?

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Francis Bievre answered ·

I don't think so the simulation weights over 700 gigas ...

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Peter Horvath answered ·

Interesting. Can you send me this data to take a look?

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Francis Bievre answered ·

Hello Peter,

I launched the same render in the standard engine, but did not create materials (if it matters but I don't think so).

It rendered my frame after around 1mn of preparation.

Tried again with Arnold and it is still exporting right now (5mn in). But I can see every few seconds in the bottom left corner of C4D "preparation of the houdini ressource", which does not seem to repeat with the standard engine.

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Peter Horvath answered ·

Can you check if the HEngine behaves the same way when using the Standard Renderer instead of Arnold? I wonder if it's something to do with the export in the plugin or the Houdini Engine itself.

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Francis Bievre answered ·

Doing some tests I think the Houdini Engine is loading every single frame each time it renders a frame. So for frame 1 it loads frame 1 only, but for frame 10 it loads frame 1 to 10 and so on.


I set my C4D project to begin on frame 64 and I rendered a frame in 4mn. But the second frame took 25 more seconds and so on …

I can't seem to find a solution that does not imply to save the project 100 hundred times and render one single frame in each one of them … >__<

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