Render Times

[danf]

What are the factors that influence render times?

[robcat2075]

materials that use complex combiners (noise) can increase render times.

 

ray-traced shadows

 

multiple lights

 

particle effects like hair or liquids

[danf]

Ahh! So my stretch of pavement that is pretty hi-res and uses a ton of tiny grains of concrete, that might be the problem??

[danf]

So here are potential culprits:

 

Cloth effects?

Roughness Texture?

Reflectivity?

Motion Blur?

Multi-Pass Rendering?

 

 

And btw, I have it in my head that multi-pass makes it look softer and less pixelated, is that the goal?

[robcat2075]

Ahh! So my stretch of pavement that is pretty hi-res and uses a ton of tiny grains of concrete, that might be the problem??

 

Hmmm... could be.

 

I think part of the problem is calculating all the details of the material, and the other part is A:M has to anti-alias all those details.

[danf]

Yeah, I have two pretty hi-res textures being applied to different ground elements. I'm thinking this could be the problem.

 

I've considered masking in actual photos of a more realistic desert ground post-rendering, but I don't want to lose the shadows of my scene's elements.

 

Is there a way to render with my ground missing as an alpha mask, but keeping the shadows as if that ground was there?

[danf]

I removed the large flickering ground texture map for a solid color and added shrubs for a more 3D sort of "texture." I'm satisfied with the result, but it's only trimmed another 20% off the render time.

 

I wouldn't be so obsessed with it, but I did some earlier shots on a different .prj, and I feel like they were rendering far faster... although it's possible they were just shorter shots, come to think of it.

[Gerry]

How many passes are you rendering at?

[danf]

Well that shot was rendered at 1-pass, which probably explains why it looks SO crappy? I've been asking that but haven't gotten an answer- more passes will kinda blend out those glitches? I wasn't sure if multiple passes would change a thing if I wasn't adding motion blur or depth of field.

[robcat2075]

So here are potential culprits:

 

Cloth effects?

waiting for cloth to simulate is tedious, but that happens before rendering so not a rendertime issue.

 

 

 

Roughness Texture?

because it has to be antialiased

Reflectivity?

yes, because objects seen in mirrors need to be rendered.

Motion Blur?

not in itself. The non-multipass MB is pretty snappy although rarely it will create odd looks. MB by multipass, of course requires quite a few passes to blend together.

 

Multi-Pass Rendering?

every pass adds time. The only gain is that each pass isn't anti-aliased.

 

I think Martin said that the regular render's AA is equivalent to a 4x4 multipass (16 passes). The regular render will almost always be faster than a 16 pass multipass render.

 

 

And btw, I have it in my head that multi-pass makes it look softer and less pixelated, is that the goal?

It takes quite a few passes to exceed the anti-aliasing of the regular renderer. The main benefits of MP are more accurate motion blur and possibly more accurate Depth of field effects.

 

very hi # multipass renders may be useful for scenes with fine details that defy good anti-aliasing with regular settings.

 

I find a 1-pass multipass render useful for testing lighting without eating up time with anti-aliasing that I don't need to see.

[danf]

That's really interesting- the non-multipass renderer antialiases to fake effects that would normally take 16 passes to achieve! That's a load off my mind- and processor!

[Fuchur]

That's really interesting- the non-multipass renderer antialiases to fake effects that would normally take 16 passes to achieve! That's a load off my mind- and processor!

 

Multipass-Renderings are generally a bit better concerning some effects and antialiasing.

It depends on the scene so, if 16 passes are the same as AA... in some cases 9 passes are good enough, in others 16...

 

In the end: I only recommend to use Multipass for still-images or if you got a real need for it... (for example: Raytraced shadows get softer by multipassrenderings, while they stay hard with AA-renderings, etc.).

ZBuffer-Shadows will render in both blurred, so it is your choice.

 

*Fuchur*

 

PS: Top 5 Rendering-Slowdowners for me:

1.) Reflection-Level too high..,! Be sure that you have the reflectionvalue at exactly the value you need... often 2 is enough. Try it out: Render an image with 2 and after that with 5... 5 will take forever and in most cases it is just not needed.

 

2.) Roughness-Values are rendering less fast than bump-maps. The Antialaising of those is very timeconsuming, so I recommend to use a Bumpmap, even so they are less easy to setup.

 

3.) Displacementmaps are really a cool thing and they can give you much better looking objects... but be careful: They take longer to render than for example a normalmap or a bumpmap... so if you are only after small details and you dont need displacementmaps, dont use them. If you however need a very detailed object near to the camera, you should use them!

 

4.) Particles - While it has gotten far better in the last versions, particles are still a big timekiller in the renderingprocess.

 

5.) Transparent Objects, especially if you are using specularity and other surfacevalues with it... worst thing: Index of Refraction.... so if you dont really need it, dont use it. Think about rendering to different imagesquences and blending them together afterwards. It may not look exactly the same and as cool as the first attemp, but it renders far faster and it is much faster to change something afterwards.

 

 

These are my top5... the first here isnt necessarily the worst thing for renderings... it highly depends on your scene....

 

*Fuchur*

[danf]

I found the element that was taking up my render time!!!!

 

I realized by just watching what it said it was thinking about during render. I noticed it was taking a disproportionately long amount of time thinking about my ground surface. I realized I had initially deleted the default ground and made my own crappy one. I don't know what I did wrong, but when I imported a default ground surface, it divided my render time by three.