Not a noob - wth did I do wrong? Grainy IRay again

Ikyoto

Stumped myself again on lighting- this grainyness is killing me

Knittingmommy

It's a really dark scene.  How long did you let it cook?  My guess is that you need longer than what it rendered at.  You can try upping the quality, too.  It might help.  For scenes like that, I usually do at least a quality of 2 or 3 and up the convergence to 98%.  I've even had to undo limits and push the iterations up well past the 15000 limit that DS sets.  My best guess is you might need to let it go up to at least 25000 or 30000 to get rid of the grain.

Ikyoto

Knittingmommy said:

It's a really dark scene.  How long did you let it cook?  My guess is that you need longer than what it rendered at.  You can try upping the quality, too.  It might help.  For scenes like that, I usually do at least a quality of 2 or 3 and up the convergence to 98%.  I've even had to undo limits and push the iterations up well past the 15000 limit that DS sets.  My best guess is you might need to let it go up to at least 25000 or 30000 to get rid of the grain.

I think it's the iterations. I had it set a lot lower (8k). Thanks for jostling what gray matter I still have.

Oso3D

If you can process exr, I'd suggest adding a decimal place to all the lights until everything is really well lit and then tweak it with hdr toning.

Oso3D

Also, if you didn't think of it, change tone mapping to 'raw'

(highlights to Off, the next thingie at 1, crush blacks to 0).

 

Etrigan

Like Knittingmommy said, time and iterations are key.

Did you have Caustic Sampler on?

My typical solutions are rather mundane:

• Increase ISO above 400 (just like film)
• Increase Render Quality to 15-20
• Increase Convergence to 98-99%
• Increase time to 14400 seconds (4 hours) or 28800 (8 hours). I don't like to do the zero option to give infinite time and most of my works have met 99% within 4 hours.

Edit: I saw this in another thread. mtl1 said: "Be sure to also use the architectural sampler for indoor scenes, as it's primarily used for indirectly lit -- ie. bounced light -- scenes. The initial iterations look grainier than the typical render, but it actually ends up being less grainy with faster convergence once it gets going :)"

L'Adair

I have learned to control the length of a render by Max Samples only. To do that, I turn Quality "off" and set Max Time to "0". Then I set Max Samples to whatever amount I choose. I think it may even render a bit faster as the software isn't checking for convergence. I usually set Architectural Sampler for every render I do. The grain will be consistent over the entire image, so when the light areas are no longer grainy, the same is true for the dark areas. Sometimes the image will render faster because I'm using the sampler, sometimes it takes longer. I don't really care, as it's the quality of the image I'm looking for. (I currently do all my renders CPU only...)

Iray seems to prefer well lit scenes. Darker scenes will always take longer. One way around that is to render it lighter and adjust the levels in Photoshop, or other graphics program. Use Tone Mapping to lighten your image. You can adjust Film ISO as Etrigan mentioned, or you can adjust F/Stop, Shutter Speed, or Exposure Value. On my camera, the different adjustments make changes in how the final image looks, but in DS, I haven't noticed any appreciable differences based on which of these four values I adjust in the Render Settings->Tone Mapping.

Also—I've been told and experience backs it up—when the light in a scene includes emissive surfaces, the number of polys of the emissive item(s) will affect render times. The more surfaces, the more calculations required, the longer the render time.

I hope some of this is helpful.

3Diva

It's easier to darken a scene in post work than it is to lighten a dark scene. So the rule of thumb (for me) is to usually render lighter than I need if I'm going for a dark scene. The render time is much faster and you lose the graininess. It's then easier to darken it in post. You can also try rendering a Beauty Canvas - that works great for adjusting light in post. :)

Fishtales

I'm the opposite of Will. I would set Highlights to 1 and Crush Blacks to 0.002 if that is too grey then raise the Crush Blacks slowly until you get the contrast you are looking for. I also have White Point set at 250/0.96 permanently.

fastbike1

Remember that Tone Mapping doesn't add or subtract light in the Iray sense (of calculations). I would try adding more light to the scene and adjusting the Tone Mapping (which you can do during the render) to be darker. I would try this in the render before trying tone mapping in Post.

dracorn

divamakeup said:

It's easier to darken a scene in post work than it is to lighten a dark scene. So the rule of thumb (for me) is to usually render lighter than I need if I'm going for a dark scene. The render time is much faster and you lose the graininess. It's then easier to darken it in post. You can also try rendering a Beauty Canvas - that works great for adjusting light in post. :)

Can you enlighten me - what's a beauty canvas?

mtl1

Etrigan said:

Like Knittingmommy said, time and iterations are key.

Did you have Caustic Sampler on?

My typical solutions are rather mundane:

• Increase ISO above 400 (just like film)
• Increase Render Quality to 15-20
• Increase Convergence to 98-99%
• Increase time to 14400 seconds (4 hours) or 28800 (8 hours). I don't like to do the zero option to give infinite time and most of my works have met 99% within 4 hours.

Edit: I saw this in another thread. mtl1 said: "Be sure to also use the architectural sampler for indoor scenes, as it's primarily used for indirectly lit -- ie. bounced light -- scenes. The initial iterations look grainier than the typical render, but it actually ends up being less grainy with faster convergence once it gets going :)"

... I was going to say this exact thing, but someone beat me to it already ;)

Richard Haseltine

dracorn said:

divamakeup said:

It's easier to darken a scene in post work than it is to lighten a dark scene. So the rule of thumb (for me) is to usually render lighter than I need if I'm going for a dark scene. The render time is much faster and you lose the graininess. It's then easier to darken it in post. You can also try rendering a Beauty Canvas - that works great for adjusting light in post. :)

 

Can you enlighten me - what's a beauty canvas?

In the Advanced tab of Render Settings go to the Canvassse sub-tab. Check the box next to Canvases, then click the + button to add one - it should be set to Beauty by default. Select all of your items in the scene, then click the Nodes button under the Canvass list and seelct Create from Selected. When you render and save a folder will be created in the save location with an .exr format version of your render - that has much greater detail (higher-bit colour) than the plain render file and can be adjusted much more freely without posteristation.

dracorn

Richard Haseltine said:

dracorn said:

divamakeup said:

It's easier to darken a scene in post work than it is to lighten a dark scene. So the rule of thumb (for me) is to usually render lighter than I need if I'm going for a dark scene. The render time is much faster and you lose the graininess. It's then easier to darken it in post. You can also try rendering a Beauty Canvas - that works great for adjusting light in post. :)

 

Can you enlighten me - what's a beauty canvas?

In the Advanced tab of Render Settings go to the Canvassse sub-tab. Check the box next to Canvases, then click the + button to add one - it should be set to Beauty by default. Select all of your items in the scene, then click the Nodes button under the Canvass list and seelct Create from Selected. When you render and save a folder will be created in the save location with an .exr format version of your render - that has much greater detail (higher-bit colour) than the plain render file and can be adjusted much more freely without posteristation.

Gotcha.  Thank you!