Choose the right Kernel
The Direct Lighting Kernel is the fastest kernel but it’s not as physically accurate as the Pathtracing or PMC method, use it if you can! The PMC method is the slowest to render – we never use it unless we are trying to create caustic effects – but it is always much slower.
Lower the Samples
Choose the minimum sample value that gives you an acceptable level of noise/ grain. If you use the AI Denoiser you can take it very low, even to 300 in some cases. Higher values will keep fine details but render more slowly.
Too high a value will give you fireflies (which can need A LOT of samples to clean up) – bring this value down to 1-10 and it should clean most of the fireflies up
Optimize your Geometry
The less geometry the faster the render! 3D scanned models are notoriously huge! Retopologize if you can.
Remove unnecessary objects and materials
If it’s not visible in the shot (or in reflections/refractions) get rid of it! Everything eats up VRam!
Limit the amount of lights in your scene to only what is necessary. Light materials (Blackbody and Texture Emission materials render even slower – try to limit these)
Slow Material Types
Specular Material Types are the slowest to render (Like Glass or Liquid) especially if you are using a Medium (subsurface scattering) if it’s not necessary – replace it with a more simple material like Diffuse or Glossy.
Octane handles Displacements very well but they can still slow your renders – especially large 32bit images – if you can get away with Normal or Bump maps instead, do it!
Texture Map Size
8bit images render faster than 32 bit images and use less VRam – if you can sacrifice detail use smaller images!
Bake those simulations! Otherwise those extra calculations will slow you down!
If you can replace your Area Lights with a HDRI map – do it! HDRI lighting renders MUCH faster!
You can use the denoiser to clean up that sample noise which will let you lower the sample count way down! Doing this will speed up your renders dramatically! Don’t over do it though, especially for animation – you can get flickering and loss of detail if the samples are too low!
Can render the less detailed areas of a scene super quick by turning pixels off when they reach a defined sample threshold. Don’t go too crazy with this or you’ll end up with noisy images.
If you have VRam to spare
Increase your Parallel Samples and Max Tile Samples