General tips for speeding up render times?

[thenomad]

I've just bought Octane Render, and I've almost immediately noticed that some things seem to slow down or speed up rendering much more than I'd expect. (Notably, Forest Pack mentions that opacity maps slow down Octane, which surprised me).

So, I'm wondering if there are general best practises for materials, geometry, features etc to use or not to use for best rendering speed? Are there hidden gotchas that'll slow the rendering right down, like excessively large textures, specific map / material types, particular lighting setups, etc?

I'm generally moving assets from Daz3D to 3DSMax, along with using some procedurally generated terrains applied as displacement maps.

(Apologies if this has already been covered a million times - I couldn't find anything in the forums but maybe didn't search hard enough.)

[MaTtY631990]

Hi thenomad, welcome to community.

I will try my best here to explain with general notes that will cover any type of scene that would be used.

* Use as few polygons as possible for mesh lights and as few lights is possible for the engine to give fastest results. Engine is not optimized yet to deal with hundreds of lights efficiently.

* Materials that use SSS / Absorption will slow down the overall rendering due to complexity of the nature of the process so if you need to try alternate methods to achieve similar results. Looking on forums you'll find a library of topics to do this.

* Opacity maps will slow down rendering since it needs additional processing for light to pass through. If you do not need this you can turn of alphashadows for faster speed.

* Use Direct lighting GI mode with few number of bounces for fast quality results.

* Layered materials will slowdown the scene depending on complexity.

* Large texture sizes will require more memory and should have minimal effect is rendering speed.

* Interior scenes that have small areas of where light is passing through will be more efficient when using portals.

Hope this helps

[mib2berlin]

Hi, if you use PT or PMC kernel the default samples setting is 16, you don´t need so much bounces often.
If you have no specular materials 3-4 is enough and for glass 4-6.
To low samples result in black areas in glass so you see this very fast.
Many good pictures in gallery are DL diffuse kernel or DL ambient, these are the fastest render kernels and are suitable for many projects. Use fake shadows in specular materials when needed.

8 Titan are also very good to speed up render times.

Cheers and welcome, mib.

[thenomad]

That's fantastic - thanks very much.

I can confirm that I've already tested the impact of turning alpha shadows off, and it reduced render times on my scene by about 50% at 200 samples.

I'm using layered materials for terrains - what are the upper limits on number of layers before things start slowing down?

Also, what's the fastest material overall, or does it not make a lot of difference? I've been using Diffuse for most things, but I recall Sam Lapere mentioning on his blog that the Octane Glossy material is very fast to converge...

[MaTtY631990]

Materials that have 4 and more will probably slow it down. It all depends really in what processing each requires at the end of the day.
Also yes, to say that glossy is the fastest and can be used as diffuse as well if you want to go that way.