note on memory usage when rendering lots of particles

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Hi,

I just want to share an interesting observation. Recently I generated about 100m particles (using the usual seeded technique), merged them together and tried to render it (using a delayed load procedural to save as much memory as possible).

Now, my render consumed about 50GB of memory (I shot that one down), then I tried to remove the particle system primitives (I had one for each seed), so at the end my files contained only points. This time mantra rendered it with using less than 10GB (!) of memory (it was 5-6GB if I remember correctly).

I was aware that mantra doesn't need the particle system primitive anymore to render particles, but I didn't know about the memory consumption implications.

cheers,

imre

ps.: The fact that it can render 100m particles using only 6GB – mantra _rocks_ big time.
Imre Tuske
FX Supervisor | Senior FXTD @ Weta FX

qLib -- Houdini asset library
http://qlab.github.io/qLib/ [qlab.github.io]
https://www.facebook.com/qLibHoudini [www.facebook.com]
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Points as particle systems actually render as spheres by default, whereas without the particle primitive they are simply points. That's my guess as to why they took so much more memory.

-Jon
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thank for share
I just have a question that after I delete particle system(use delete SOP and keep points) those points will be can't render with uniform volume ( I want render for spray )
maybe I should use other shader for render spray? any idea will appreciate
thanks!

iGou
Edited by - June 5, 2013 10:53:09
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In a VOP material you can use the Lighting Model node, set to ‘isotropic’, or use the ‘physically based phase lighting’ node. Modifying this and the opacity should give you a more volumetric look to your particles.
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In a VOP material you can use the Lighting Model node, set to ‘isotropic’, or use the ‘physically based phase lighting’ node. Modifying this and the opacity should give you a more volumetric look to your particles.
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Hi Jpparkeramnh:

Thank you for your advice! Sorry that I don't know much about Lighting Model. The way I have is to first create a VopMaterial in SHOP, then create a light model and connect it to Surface output (as the image below). However the result is looking weird… may I ask for more information on the settings of materials please?

Thank you for your time
Edited by - June 7, 2013 22:08:05

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You should modify opacity with another VOP, like a constant or noise.

Generally points don't look good large and up close, and the answer is usually to generate many many more of them so that the individual points are no larger than a few pixels on-screen. This way they all average together to create a more complicated look. The sum is greater than its parts, as they say.
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You should modify opacity with another VOP, like a constant or noise.

Generally points don't look good large and up close, and the answer is usually to generate many many more of them so that the individual points are no larger than a few pixels on-screen. This way they all average together to create a more complicated look. The sum is greater than its parts, as they say.
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I see. thank you for your help
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jparker
Points as particle systems actually render as spheres by default, whereas without the particle primitive they are simply points. That's my guess as to why they took so much more memory.

-Jon

Hey, thanks, that's good to know…I'll check this out as soon as my time allows.

cheers!
Imre Tuske
FX Supervisor | Senior FXTD @ Weta FX

qLib -- Houdini asset library
http://qlab.github.io/qLib/ [qlab.github.io]
https://www.facebook.com/qLibHoudini [www.facebook.com]
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