Tips to speed up rendering

[carlotristan3d]

Kindly share tips to speed up rendering in mental ray.

[CJI]

Thats a little vague to be honest. Your settings will depend on your scene, Its size, and content. Is it indoor or outdoor, Lighting system etc. It will be hard to get answers from anyone without a more detailed input.

 

A quick look through the forum will give you general guidelines from where to start.

[ihabkal]

A- buy the fastest computer you can afford

B- check Gnomon school DVDs about Mental Ray, or check the web for free tutorials if you spent all your money on the computer.

[carlotristan3d]

Thats a little vague to be honest. Your settings will depend on your scene, Its size, and content. Is it indoor or outdoor, Lighting system etc. It will be hard to get answers from anyone without a more detailed input.

 

A quick look through the forum will give you general guidelines from where to start.

when using scanline for example, you can reduce the maximum depth on your raytrace settings. this speeds up your rendering time without affecting the quality of your render. i'm sure there are some tweaking on mental ray.

[CJI]

ok then.

 

Final Gather

 

Keep point density low - Lower Numbers = Faster, Higher Numbers = Slower Renders. Try to keep it as low as possible. Always the last figure i adjust and only when absolutly necessary. Usually keep it at Draft settings of 0.1. Up your Rays per FG point setting and interpolate over Num. FG points instead to keep render times down and try to clean up the render.

 

Diffuse bounces will eat up render time with little return over the 4 times setting.

 

Pre calculate your Final Gather Maps where possible to save time for final render and you can calculate these quite a bit smaller. sometimes even half your final resolution.

 

Cache your geometry to save on translation time.

 

GI is usually good as is, i have even lowered it at times.

 

Lower samples per pixel reduce render time but increase jagged edges. min 1 max 16 is usually fine for finals but you may need to go higher.

 

Ok. these are just basics, Mental ray is much more complex than the scanline render. Your materials will also have a large effect on the render time. And like i said, these settings are often scene dependant, what works for one won't necessarily work for another and considerable tweaking of values may be necessary to get the desired result.

 

Hope this is what you were looking for.

[RevitGary]

http://forums.cgarchitect.com/38854-render-times.html

 

Check out my post on the same subject. Some good tips on portals there. Any other tips are welcome.

[Crazy Homeless Guy]

- Work in manual mode. This will allow you to control photon shooting per light, meaning you won't be calculating needless photons.

 

- Turn off specular reflection on all but the lights closest to the camera.

 

- Use a fall off limit on your lights.

 

- Use no more than 16 subdivisions on shadows.

 

- Use Box 1,1 for AA, and 1-16 sampling. Then sharpen in post.

 

- If you have glossy reflections in floor materials, or frosted glass materials, seriously consider rendering them in s separate pass.

 

- Turn off area shadows on all but foreground lights.

 

- Remember the two things that slow down most GI engines are sampling and AA. This is true at both material level, and global level. Be very critical of your use of both of these.

[anejo]

Remove any objects, materials... that's not in camera view.

[Crazy Homeless Guy]

Remove any objects, materials... that's not in camera view.

 

I just laughed out loud because I misread the post. At first I thought you told him to remove everything in the scene, and then hit render to speed it up.

 

That would do it though.

[CJI]

I did the same thing. HAHAHA if only it was that simple eh.

[mattclinch]

keep your model as close to the origin as possible and optimise your BSP settings. first thing i do before hitting render. can save hours.

[CJI]

Hey Matt, I was wondering if you could clarify the BSP thing. Not entirely sure what i should be doing there. My understanding is that Bsp1 is quicker for non complex scenes. Whereas BSP2 is for more complex scenes. Not entirely sure how it effects rendering in the first place so have tended to leave it be.

[mattclinch]

Curtis - this link explains it all better than i ever could.

 

http://www.bernardlebel.com/wiki/index.php?title=3D:XSI_tutorials:BSP_Explained_To_Artists

[anejo]

I just laughed out loud because I misread the post. At first I thought you told him to remove everything in the scene, and then hit render to speed it up.

 

That would do it though.

 

you know me well enough Travis that i would never say anything sarcastic like that. or would I?

[RevitGary]

Curtis - this link explains it all better than i ever could.

 

http://www.bernardlebel.com/wiki/index.php?title=3D:XSI_tutorials:BSP_Explained_To_Artists

 

How does all of this work with BSP2?

[mattclinch]

How does all of this work with BSP2?

 

As far as I'm aware, BSP2 is a method allowing calculation, caching and flushing of the BSP tree depending on the area of the model being rendered rather than entire scene in one go in order to reduce the RAM overhead. Useful if you're running low levels of RAM, but ultimately the flushing and caching adds to your render time, up to 20% on occasions compared with an optimised standard BSP tree, I believe.

[RevitGary]

The bsp tree thing I read the link.

 

It seems all one needs to do is adjust the depth for an orange color in the diagnostics. and make sure the scene is near the origin point .

 

Am I missing something?

[RevitGary]

I seem to recall you need to use BSP2 if you want to use mental ray proxies?

[Peter M. Gruhn]

My (blind leading...) understanding is that deal with BSP2 for proxies is that BSP2 allows for on demand loading of a proxy's contents. Thus the whole model needn't reside in memory, only the bits being used. Without testing it, I would guess that this is actually a speed hit. The benefit here is in terms of memory use - HUGE model, modest memory needs. Proxies work ok with BSP/1/.

[danb4026]

Is there a script that would do that?? Would be very helpful!

 

Meaning....remove objects and/or materials on objects on those that are out of camera view.

[carlotristan3d]

i reduced the trace depth, max reflection and refraction to 2,default is 6 and it cut down rendering time in half. and there are no obvious difference unless you zoom in to reflective objetcs.

[DanGrover]

Is there a script that would do that?? Would be very helpful!

 

Meaning....remove objects and/or materials on objects on those that are out of camera view.

 

I think such a script would be easy to do, but a bit too ... insensitive. That is, if an object just pops out of view, it may well affect the shadows, the GI, the colour bleed, the reflections etc. I think the only reasonable way to do it would be by hand, as no script would know what's important to you in a scene. I suppose if you went mental you could script one that checked if there would be any shadow movement or reflection changes or GI changes in the viewport, but I'm pretty sure that would basically involve re-rendering the scene just to check. Ultimately, it'd end up taking more time I think.