1st ever smoke render - very granular & not smooth

[Junior41]

Hello,

I'm attempting my first project using smoke as a density volume through which an identical volume collides, generated from VDBfrompolygons. I can't manage to figure out why the render appears so grainy - sample JPEGs attached.

The VDBfrompolygons voxel size is 0.1, & my smoke object division size is 0.1. 

I've made sure the rendering engine is micropolygon PBR. I'm using a couple of hlights & a sunlight, making sure they're set to "Depth map shadow" shadow type, shadow quality set to 2 & pixel samples are 2x2. My experience with lighting is extremely limited, so any feedback regarding this would be valued very much. 

The whole scene looks so much cleaner in the scene view than in the render view, not at all realistic as I would expect it with the application of shader materials to the objects. I must be doing something very wrong. 

Thanks in advance for any ideas. 

[celd]

If you use raytracing or pbr render engine you can increase stochaistic samples up to like 128 to remove most of the noise without increasing render time too much, otherwise you are gonna need to bring pixel samples up - the value you are using is simply too low.

Also your volume does not appear grainy in the viewport because it is being rendered by OpenGL, completely different than mantra.

[Junior41]

Thankyou so much for your advice & insight. This is very much appreciated!

[TobyGaines]

I don't think 2x2 pixel samples is high enough to render any scene in the universe without noise. 7x7 is about medium quality (all things being equal), I've had to go up to 18x18 for tougher scenes.

 

[Junior41]

4 hours ago, TobyGaines said:

I don't think 2x2 pixel samples is high enough to render any scene in the universe without noise. 7x7 is about medium quality (all things being equal), I've had to go up to 18x18 for tougher scenes.

 

Thanks for your advice! I've read I believe in a Peter Quint comment he made on one of his tutorials that the Minimum Ray Samples acts as a similar threshold for output quality, but with quicker render time. Is this accurate, or is Pixel Samples a better way of generating quality output? This particular scene is 360 frames in length, taking me some 20 hours to render at the moment. 

Also, do you have any thoughts on outputting the rendered .exr files to high definition video? The Export to video fuction within MPlay seems to deliver poor quality .avi output? 

Very much appreciate any advice on this. 

J

[TobyGaines]

It would be quicker, if it worked  Not all scenes are the same, and I'm sure his trick doesn't mean that you can 'lower' the pixel samples. I've tried raising ray samples alone to fix noise, and it's been slower and still lower quality than having enough pixel samples. So now if I stray from the ray sample default of 1 / 9 @ 0.01, it's done in combination with higher pixel samples.

20hrs for 360 frames ( 3.5 min. per frame ) on one home computer is not slow by any means! Plan on taking several days to render that many frames or buy more computers.

I use Nuke to render the exr's to .png, then bring them into Quicktime 7 pro to render video, but that's just hobby-level stuff, I haven't tried using Mplay to do it - do you see any compression settings for it?

[Junior41]

On 08/05/2019 at 12:06 PM, TobyGaines said:

It would be quicker, if it worked  Not all scenes are the same, and I'm sure his trick doesn't mean that you can 'lower' the pixel samples. I've tried raising ray samples alone to fix noise, and it's been slower and still lower quality than having enough pixel samples. So now if I stray from the ray sample default of 1 / 9 @ 0.01, it's done in combination with higher pixel samples.

20hrs for 360 frames ( 3.5 min. per frame ) on one home computer is not slow by any means! Plan on taking several days to render that many frames or buy more computers.

I use Nuke to render the exr's to .png, then bring them into Quicktime 7 pro to render video, but that's just hobby-level stuff, I haven't tried using Mplay to do it - do you see any compression settings for it?

Really useful advice, thanks for taking the time to respond. 

Yes there are compression settings in the MPlay, however I've only just discovered the Gamma setting - didn't know what this was previously & hadn't adjusted it. This now gives an accurate output of the Mantra render. 

However there is a glaring discrepancy between the "Render view" render & the "Render to disk" output from the Mantra node in the 'Out' context (pics attached). The "Render view" shows a blue background & fog volume shaded with a warm Area Light which is what I want, however the Mantra render saved to disk outputs a plain white fog volume & the blue background has strange uniform vertical patterns. I've spent hours trawling through the setup, materials, lighting, Mantra settings & can't understand why this is occurring? Is the "Render view" output not supposed to be a true representation of the Mantra node settings?

Any assistance or thoughts would be highly valued! 

Thanks again for your time.