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Juraj

Slow render of empty (black) area of image

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Hi,
I am rendering with Arnold a scene which contains really small portion of frame. Maybe 5%. Rendering of this part is really quick as shaders are just flat colors without shading, GI, glossy etc...
But rendering the rest of the frame - empty, or black area takes much more time.
Is there a way to render only part of frame which contains geometry and maybe a little padding (for motion blur)? Because it would speed up my renders up to 10x times :)

 

Thanks,
Juraj

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Guest tar

Mantra can use the Crop Mask on the Camera.

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hi,

never happened to me, but see a few ideas:

have you tried to turn on autocrop in arnold? is it possible that it comes from messed up motion blur/dof or anything like this? did you cache the rendered objects prior rendering? are there any other objects in your scene that doesn't have to be there? if so, delete them.  have you tested whether the slowness come from lighting? (try turn off lights and render the scene with only one default direct light). does log say something? cheers. d. 

 

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@davpe I tried autocrop option, but it seems to be performed after rendering and is useful for comp application. I didn't notice any effect on rendertime. I have no lighting in scene, just flat shaders, but my AA samples are relatively high - 9 because of motion blur. The scene renders quick still but would quicker if computational time wasn't wasted on rendering black area of frame.

@marty Crop Mask option is available also for Arnold camera, but I cannot get it working (even in Mantra). Setting manually top, bottom, left, right crop parameters works perfectly but selecting object in Crop Mask parameter doesn't work for me. This parameter should do what I need but I don't know why it doesn't work. Any suggestions?

 

Thanks for replies

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hm... what are your rendertimes? unfortnately, arnold doesn't offer any other rendering method than path tracing. with mantra, i'd suggest you to switch to micropolygon engine as you don't need any fancy raytraced stuff of course.

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It works in the latest build - 15.0.504, and I think it was a recent fix, the journal search isn't working currently.

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@davpe Rendertime in Arnold for one frame is like 1 minute. When I specify rendered area in IP for area containing object it is 10 seconds.

 

@marty Thanks!, will try that :)

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