View Full Version : fur as grass and mental ray

11 November 2006, 06:24 PM
I just started using MR not long ago (and probably stiill a noob maya user) and are still groping aroudn in the dark.

I'm currently working on my first short, and are running into heaps of problem trying to render with mental ray. problem being, i have trees in my scenes, and those tree's leaves used fur as leaves. now one frame with a single tree will take as long as 1/2 hour to render with a production quality on mental ray (my pc is intel 2.6ghz HT) . I also included fur shading to my lights which explains the immense render time.

Here's my question.

If most of my objects are organic, do i need certain setting in MR? as of the moment, i used HDRI, Final Gathering and GI, with ray tracing. the accuracy/rays were set to around 100. i have no idea wat the radius and other setting is for, thus i left most of it blank. I tried faking Gi with DomeGI mel for fster rendering time but the "leaves" turn out horribly geometric. (Can anyone take some time to explain what MR attributes are about? i can't seem to find a good tutorial on the net that does that)

Here is how the final render looks.. and i almost died waiting for it. I tried lookign for the best setting without wasting so much render time but due to my scarce knowledge in MR, i can only test the values here and there and hope they turn out right.

also, there'll be grass aroundn, i was thinking should i use fur again as grass, or PFX convert to poly method for MR rendering, but either way they'll be too slow.. i'm not sure about texturing grass, it might not match the style i'm going for.


Apparently I don't need to turn on final gathering for organic modeling (as well as turning off reflecction and refraction - i have yet to try) just enable occlusion thingie in shader... but fur doesnt allow specific shader assign to it does it?

Any advice would really be appreciated.

11 November 2006, 10:38 AM
okay maybe i should be more specific. here are the settings i used for this.

One ambient light for general lighting
One spotlight with furshading enabled + ray trace shadow

MR setting (quality presets set to production - below are the values i change myself)
Image Based lighting based on HDR map
raytracing - reflection and refraction - 5, trace depth - 10
shadow method: segments. motion blur shadow maps on
GI - GI accuracy - 100, radius - 0
Photon - Volume accuracy - 100, radius 0, max reflection and refraction photons - 5
Final Gather - Rays - 100, Min Max radius 0.

the rest of the settings are by default, production presets.

because this tree involves fur as leaves, its immensely slow. any way to reduce the rendering time? what setting can i reduce?

11 November 2006, 03:33 AM
i dont think i can help too much, one thing to remember though is that mental ray changes maya fur into polys when rendered, so if u have 100,000 fur's(how ever u say that :-) ) then that is all converted to 100,000 or more polys(more than likly more) i found that the reflections in my scenes are what took so dang long to render, but that is needed alot of time, with ur style in may not be.

i would try some kind of poly with an alpha map for the grass, it may take a little longer to set up but if will render like a million times faster than having all that fur.

look for ctrl_fur in cgtalk also to find a way to put a shader on ur fur, i havnt used it but there are some who have.

i dont know much about compositing but that may be the best way to tackle this job.

but for now it seems to be a test render take ur anti-aliasing samples down low, like -2 to 0 and that will help alot too.

like i said, im not too sure this helped at all but maybe more can add to this??

11 November 2006, 06:30 PM
hey malibubob

thx for the reply. now at least i know how furs are rendered in MR. i think the best way to tackle this now is to scale it smaller and reduce the leaves size accordingly to get the best looking tree.

about alpha mapping grass, the grass effect i'm trying to look for has a rather cartoony feel to it as oppose to realistic looking, hence, the fur, cause i can fatten the length and render it out in MR and it looks fine. you have any suggestions to that? i'm not very sure how to really do grass this way.

i'll try your suggestions for the render setting.

11 November 2006, 02:07 PM
nobody can help? anyone? :sad:

12 December 2006, 02:11 AM
Malibubob certainly has a good start in effort to optimize this render. It will definately speed up the rendering by much.
One other consideration you can keep in mind is indeed to refrain from using the fancy lighting tricks like GI/FG and to use regular lights to light up the scene. You would simply not require them for the cartoon-like style you're going for. It might take some more effort at the start to get "the feel" of how to light this type of look, it will be well worth it.

Also you might want to review the section in the manual dealing with BSP settings, when set incorrectly your renders can take up enormous additional time than necessary.

After that, other than decreasing the scene's complexity, renders simply take time to process especially one one single machine.


12 December 2006, 03:27 PM
ok thx for the feedback. i guess i have no choice but to turn off FG and GI. maybe i'll render the leaves seperately as my other scenes still require FG and GI, and then composite it together. that'll probably the best way to go for now

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12 December 2006, 03:27 PM
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