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[novice] reducing noise in simple Mantra render

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Just getting my feet wet with Mantra but am already battling noise issues.

In the attached render I am already at 10x10 pixel sampling with a .01 Noise Level yet the noise is still unacceptable to me, not to mention a too long render time for such a simple scene!

Other than decreasing my Noise Level value further is there anything else I should try to reduce my noise levels?

cornellBox_mantra_10x10_.01.JPG

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hi, your noise is likely coming from indirect bounce. best sliders to battle this are min/max ray samples (1/9 is quite low) and noise level. these work together so you want to hit the right balance between them. also, diffuse/reflection/refraction quality is something you may want to take a look at. add different channels to your render and inspect them to see where the noise is coming from exactly and what settings make it go away most efficiently. Also, check the sampling on your area light. If it is 1 you may want to bump it up a little (2 or 3 should do) to get rid of the noise in shadow areas. Pixel samples is global sampling multiplier. Helps get rid of all kinds of noise but it is too expensive one to cling to. If your contours and alpha have clean lines play with the above mentioned first. However, in some cases I end up having best results with Ray variance antialiasing off and using just a pixel samples. But this picture is probably not the case. Check documentation. In part about Mantra it explains nicely how to identify different kinds of noise and strategies to clean it up.

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Thanks! Great info. It seems eliminating noise in any rendering engine is part art, part science

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Check this thread for a wealth of information on noise and how to combat it:

 

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Also: this great post from Old School

 

 

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eetu,

thanks. Read( and re read) the entire first thread!

As to the 2nd thread, Rohan has been a huge help to me, answering a great many questions I emailed to him and have also gone thru most of his tutorials.

Just curious, have you done any more recent Redshift tests?

Invested in a Titan X P so for my personal work plan on focusing exclusively on GPU rendering...but want to get a handle on Mantra first. Any CPU based animation renders will be sent out to a cloud service like Gridmarkets.

As a novice one thing I am surprised by is Houdini's lack of any simple gui based tool for batch rendering. I assumed it would be like batch rendering using Adobe Media Encoder or even After Effects. Just drag and drop your files to a gui window:)

Edited by eco_bach

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Quote

 

simple gui based tool for batch rendering.

You can create many Mantra nodes then connect them to a Merge node you drop down inside your ROP network. Then when you click the Display flag on the Merge node each Mantra node will render in que, just like other batch processing applications. The order the nodes are connected to the Merge is the order the renders will occur.

Edited by Atom
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Atom

Thanks for the great tip! The power of nodes :)

Edited by eco_bach

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Here is a chart from the docs of a previous Houdini version (not sure which one) that has helped me a lot. For some reason it's no longer in the docs, but you can hunt it down if you look at the documentation in H12 or H13. Another thing I have read over and over again in the docs is that you should never really go above 6 pixel samples (they mentioned 9 as being ridiculously high and you should only go that high if you have very fine displacement details which aren't being rendered properly. Almost everything can be fixed with the min and max ray samples and the noise level. And of course using the quality and limit controls if you have a problem with reflections/refraction/GI. Following the chart solves all my problems most of the times! Hope its useful :)

SamplingWorkflow.jpg

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another quick comparison rendered in Redshift same resolution

27 seconds running a Nvidia TitanXP. <15 seconds if I reduce # rays, increase minimum detail threshold and use Irradiance Caching only. I know there are a good many caveats with GPU renderers in general but for simple scenes I can cut my render times down considerably.

redshift_27_secons.jpg

Edited by eco_bach

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