Here I have an ongoing collection of ways to speed up render times in all of Blender's engines. I strongly encourage you to use these with wisdom and not just do them. It's important that your scene still functions - these tips are for scene optimization, not scene destruction, haha. Use wisely and as always, at your own risk!
(start with these)
- Turn off particle systems that will not have any visual impact on the final render
- Reduce the sampling of any and all effects to the point where they give the result you want, without being excessive
- Minimize the need for compositing as far as possible. The compositor is not the fastest and the more nodes you load in, the slower it becomes (logical, but often overlooked).
Keep the resolution realistic to your system. Most machines can do at least 50% HD comfortably and finally full HD. Going higher will require more of everything, not just render times.
Keep it realistic to your project. Any standard frame rate between 24fps and 30fps should be more than enough - 50fps or 60fps doubles render times.
- Turn off whatever you don't need. If you don't need reflections, don't turn them on. If you don't need refraction, turn it off. If you don't need ray-tracing, turn it off. If you're not using the sky, turn it off. This goes for anything that does not contribute to the final result. This kinda sums up the entire page in one phrase - TURN IT OFF! hahaha.
- Let Blender use all your CPU's threads and give it priority.
NOTE: If you still need to use your PC, at least one Windows, you can still give it access, but make Blender's processing priority low. This will slow down the render times a bit, but you'll still be able to do other work while rendering.
A classic in the Blender arsenal, Blender Render, aka Blender Internal, is pretty much considered a thing of the past. Having said that, I can promise you that it will be a render engine used for years to come and currently (at the time of writing this, 2017 - 08 - 15) there are plans to move it to an Add-On status, which means that since it would not longer be part of Blender's core, it can be fixed, sped up, and improved on. In the meantime, and regardless of it's status, you can always find older builds of Blender with this awesome engine in it and use these tips to make those renders move along a bit faster! :D
5 samples is truly enough. The standard setting is 8, but I encourage you to put it at 5 - it will drastically reduce render times, especially with full sample enabled. Changing the filter has very little effect on speed, but does change visual appearance - Mitchell-Netravali is the sharpest in terms of picture clarity.
- Sampled Motion Blur
Just don't. Use Vector Blur in the compositor. It's much faster and still looks nice.
Turn off whatever you don't need. I never use an environment map, so that and SSS are always turned off by default for me.
Turn off Free Image Textures. Like the tool tip says, it is for freeing up memory for the compositor. These days, this shouldn't be a problem for memory and will mean that for every new frame rendered, those textures need to be loaded again. For animations, turn it off. For single renders, keep it on.
As for tile size, keeping it about 40 or so tiles per frame is generally the fastest when it comes to Blender Render.
256x256 for Full HD
125x125 for 50%HD
Not guaranteed to always be the fastest, but generally has proven to be.
Acceleration structure is best left on Auto as messing with it can potentially radically reduce or radically increase your render times.
Turn on Instance support. It helps with the scene building times before the tiles begin to be built if you have duplicates (like particles and dupliverts for example). If you don't, rather leave it off.
- Post Processing
Turn off Compositing if you're saving all passes in OpenEXR format.
Fields is for Interlacing the output for older model TV's. Please don't use it, even for older TV's - it gets de-interlaced anyway.
Image format - Here you don't get much of a difference in terms of time, but you certainly get a huge difference in file size. OpenEXR is the largest (saves all render passes) and JPEG one of the smallest with superb quality.
Video Format - A massive difference comes in with the encoding of certain formats - and the greater the resolution, the greater the difference. H.264 has proven to be one of the fastest in this area. Follow YouTube's format recommendations for good quality at lower file sizes. NOTE: Royalties apply for distribution in certain formats - do your research.
A huge time saver in terms of render times. I've found that, for example, complex procedural textures, when baked, render tons faster. Baking as much as possible can save you a lot of time, but there is a caution to this - you can't change things. If you do, the bake would no longer be accurate and you'd need to bake again. If you have to bake too often, you're wasting some or all of the time you would've gained (not saying they are equal, but a rebake takes a while for sequences and that time gets subtracted from the time saved by baking - which can be a lot as we'll talk more about lights and so on).
Under Include we have our basic passes. Like I mentioned before, removing as many as possible, without compromising the layer, is the approach. For most people, turning off Halo, Edge, Freestyle and Strands are first. Then we get to whether we need the sky or not (if excluded, the alpha pass becomes useful - which can't be turned off). Basically, the least you'd need here are ZTransparency (if you use ZTransparency in your materials) and Solid and you add from here whatever is in your scene or whatever the layer requires.
Turn off whatever your scene doesn't have. If you aren't sure if it needs it and that it may take out something you need, test it. Usually, you'd turn off:
* Emit (materials with an emission value - direct or by texture)
* AO (ambient occlusion, rendered wether used or not when environment lighting is used - world settings)
* Environment (environment lighting)
* Indirect (indirect lighting bounces - world settings, environment lighting, approximate)
* Reflection (anything with mirror turned on - sampled or not)
* Refraction (anything with an IOR value like RayTraced transparency)
Again, if you have these materials or things in your direct view, don't turn them off, or it will impact on the visual quality of the scene.
Also, whatever passes you include to be delivered to the node (ticked passes) also take up more render time.
View Map Cache is extremely useful with large amounts of Freestyle objects. Can save about a second or more per frame, but it all adds up.
Culling helps disregard some edges that are unseen
As far as LineStyle goes, just keep the modifiers to a minimum to help it process as fast as possible. The more you add, the longer it takes.
With Freestyle though, less is more when it comes to geometry. The less geometry you have, the greater the speed you have. The more you have, the likelier your computer will freeze. I've had this issue with Esther 6, so I used Edge in combination with compositing and Freestyle to outline the people of a crowded Susa.
Simplify is a great tool that is designed to knock out geometry as far as subdivisions are concerned. It allows you to limit, the maximum number of subdivisions a scene can have. It also allows you to limit the AO and SSS quality and turn down the percentage of child particles for the render. A truly useful tool for viewport previz and to cap settings for your renders so that if you go too far without realizing it, Blender can knock it back for you.
- Ambient Occlusion
A feature that looks amazing, but takes up a lot of render time. Leave it off if your scene doesn't need it or bake it if you can.
- Environment Lighting
Again, adds tremendously to render quality, but the sample count can really lengthen the render times. Reduce the samples to 1 and the distance to 0 if you just want your scene lit with only a light load.
If you do need environment lighting with some distance, you can use about 7 samples with the Adaptive QMC and it's threshold set on 1. This threshold means that the moment Blender believes the bounces will no longer make a difference, it will stop calculating - the higher you set it, the quicker it stops (again, slightly more noise, but much faster render). Meaning, your bounces will be 7 and lower. Adaptive QMC works faster, though a bit more noisy than Constant QMC.
- Sun, Point, Spot and Area Lamps on Ray Shadow
No Shadows and nothing else enabled is ideal, but this doesn't work for every scene. In fact, doesn't work for most scenes.
The second best is to leave off any light specific settings (like Sky and Atmosphere for the Sun Lamp) and to make the light samples 1, select Adaptive QMC and make the threshold 1. I have seen a difference after making these changes, so I'm recommending it - even though, theoretically, the latter two are not supposed to make a difference if the shadow samples are set to 1.