Slow Renders (help with workflow please!)

So I’ve been working with blender for a few months now and have gotten comfortible with it, but as my scenes have become more complex, I’ve noticed render speeds have greatly slowed my progress. I’ve been fairly careful about not overusing raytracing, but I still find myself waiting a lot, even on my fairly decent quad core.

Is this just part of the deal? I hear about multi-hour long renders on here, mine are still only a half hour or so…

Any tips? I know my question is general, but hopefully someone can point me the right way?

Cheers in advance!

Might want to check out the poly count in your scenes. I know that you can bake high poly meshes into a normal map and use that on a lower ploy model, but I haven’t figured out how to do that yet. Sometimes there’s nothing that you can do about long render times, comes with the game. Also, if you’re using AO, Approximate is faster, but not quite as good. Using hair particles, strand rendering is good, but not compatible with raytraced shadows. But I highly recommend using both AAO and strand rendering because the difference isn’t really that noticeable.


Are you are saying a half-hour per frame?

Optimize your scene. Move different parts on to different layers and figure out where the bottle neck is in your scene. For instance, I often setup a background layers set, a mid-ground layer set, and a foreground-layer set. I keep lights on their own layer, that way I can totally disable lights and render only with Ambient Occlusion.

It is hard to say without seeing the scene.

Are you using an external renderer?

My poly counts vary, but are always reasonable. Also when I try to do a test render with my settings using a low poly model, a lot of times the render is still pretty slow. It’s mostly AO and raymirror causing the bog down. Sometimes I wonder if I should set everything up without those, and then just kick them in at the end.

I only do stills, so its a half hour for one frame.

I was thinking of doing an AO only at the end and then blending it in Photoshop using ‘multiply’ ?

I will try approximate ao, like you said. I don’t use a ton of AO, just a bit to kick the realism of corners and soften shadows.

edit Forgot to add I use Blender Internal

A half-hour for a still is nothing. I have let stills sit and converge using Lux way longer than that.

You can try lowering your raydepth. Raydepth is zero based, so even when it is set to 0, you still get a single bounce.

“A half-hour for a still is nothing.”

That really depends on your target. If you’re doing stills, and are going for certain kinds of photorealism, you’re correct. Not everyone shares that goal though. Some people might be rendering for an animation that’s due in three days. In that case, it’s certainly not “nothing.”

While it’s true that some people on these forums have high render times, especially those using external physically correct renderers, I’d be hard pressed to believe that your scene should be approaching those heights. Even this ancient one I did (before the days of a compositor or even strands for grass) had around 2 million polys and clocked in at 2 hours for the final beauty render. That was extreme. Production render times for my last project (interior with four characters, fur + hair + lots of lamps) hung around 4 minutes a piece.

I’d work on the optimization. Wouldn’t hurt to show one of the renders at least, so we can take a look and make better suggestions.