Newbie to Mental Ray

[bcampbell]

I have been out of the 3D game for 18 months now - this is my first attempt for some time. Nice to see Max has decent renderer now as an option but I may need some help using it.

 

I have scoured this forum and have found some good tips, although not many external scene tips but shall try and pester folk as little as possible. But mental ray is definately a black art. I have mainly the building done - working up the environment just now, but all tips and tricks appreciated.

 

What i know so far:

 

I know that RPC wont work - or will have to be in a separate pass.

That using GI and FG may cause a flicker in the animation

X*Y*Z=NI - i suck at maths

This scene is already taking 37:01 to render at PAL D1 - need to get that down

 

My GI settings are:

Max # Photons per Sample:1000

max sample Radius: 5000.0mm

Volumes

Max # Photons per Sample:1000

max sample Radius: 5000.0mm

Light Properties

Average GI Photons per Light:155000

Global Energy Multiplier:0.4

Decay:1.95

 

Lights

Daylight Sytem: standard, directional, mental ray shadow map:4096, Skylight:off, Global Mulipliers:1.0,1.0,1.0

4 x mr Area Omni's: Ambient only, Global Mulipliers:0.25,0.25,0.25

 

The master is whipping me to push as many pixels per hour as possible so all help will be greatly appreciated.

 

http://www.invalidcommand.co.uk/viz

Athlon 64 3500+ (Venice), 2GB DDR 400 Dual Channel, 6600GT

[mohamedberry]

ok what i noticed is the four omni's with ambient only, why four !! one will do.

and your GI & FG radius i thinkg they are far too big, but if u get a good result then no need to change it.

i usually use a skylight for exteriors but this will need FG to be visible but i think daylight system is alternate... but still i dont like the sun possition, can find enough shadows.

great model & great start... good luck and keep posting

[bcampbell]

I am more than happy to use FG if it will help - just that I seen a post saying that it can cause a flicher when using GI and FG in animation. Yeah I thought that the radius was too high also however all i would get off my grey renders where dots everywhere - maybe I need help here. I seen a post from Joske saying that the max radius to use should be between 500 -1000mm. Sounds better to me but I need to make the decision soon on whether or not to use Mental ray - would realy love to though.

[noi-pi]

Try this but set your units to Meters:

 

GI = 500000 / Samples 2.0

Volumes 50000 / Samples 2.0

 

FG = 200

 

Light Properties: Av GI photons per light 10000

 

Use skylight with bluish gradient map on its map slot

Mr Spot as the sun set to Directional / Rectangle.

 

Depending on scene scale almost these values are standard to me.

 

Render away........

[bcampbell]

Hi Noi-NP,

 

Changed my settings as per your post - have attached an image to show the probs I am getting.

 

It's all went a bit disco!

[noi-pi]

As I said, go check your scale.

Its probably a scale problem.

Why dont you post the max file instead and let us play it around?

[bcampbell]

Noi-PI - apologies you are correct. I only changed the display units by mistake -Doh! I have rendered another sample with your settings - still just some little dots around, but I would be grateful if anyone would like to have a shot helping with the lighting for me - you can download the scene from here

 

Thanks in advance

[noi-pi]

Cannot download verde-mray.........

[bcampbell]

sorry - bad time to do a router update. Try now!

[Hao La]

why 4 omnis ?

_You can render exterior simply with 1 spot light (for sunlight) + 1 skylight

_You also dont need to worry about volume value (cause you have no volume light) just leave it default.

_The best GI photon is 1000000, increasing the Photon sample slowly until you get a good result , (leave the radius default value, that's my opinion)

_Using trace depth : 18 9 9

_Using Sample type : Michell or Lanczos ( 4 x 16)

_If your render is lacking of contrast , using exposure control with contrast level 100 , adjust the brightness until OK.

_ FG : 100 - 500 is good with the GI 1000000

[noi-pi]

Here's what I got. Its the same settings I posted earlier.

Rendertime was 8 mins including calculating GI and FG. Resolution size was 1500 X 1125 PX. You could crank up FG at a cost of rendertime.

Download the file here:

http://www.geocities.com/jon31898/verde-mray4.zip

[Karlfucious]

I am a Maya user but Im assuming that the set up is the same in Max. One thing that you could do to speed up everything is scale your entire scene down. First off this makes tuning your photons a lot easier but they also calculate a lot faster too. Dont quote me on that because I am not quite as fluent with Max as Maya but It should help a little. As far as Final Gather goes, since you are using GI you wont need to use verry many final gather rays. Probably 100-150 should do fine if you tune it right. As a rule of thumb when using a low number of final gather rays you need to set your Max Radius to 10% your scene size and the Min Radius to 1%. That way you wont get any artifacts when using such a low number. I am not shure if it is true or not but from what I hear Mental Ray doesnt like Sky light in Max verry much and is verry expensive to calculate. Instead of using that you could simply Make a light dome with a HDRI map and it should be a little faster.

 

Another option is to bypass GI and FG all toghether and use the Dirtmap shader for an Ambiant Occlusion Pass and comp everything together. Here lately Ive been using it quite a lot and have been able to get some really awsome results with relativly fast render times. Not ony is it a little faster to render that way you wont have to waste any time tuning your GI settings to get the results you are after. Using the Dirtmap shader works especially well when dealing with interior shots.

 

Good luck,

Karl

[Hao La]

Just downloaded your scene and I try to give it a shot , here is mine , not much different with your render . (I took 5min 02sec for that size of image)

 

 

Edited with Photoshop to make it more interesting

[bcampbell]

Just downloaded your scene and I try to give it a shot , here is mine , not much different with your render . (I took 5min 02sec for that size of image)

 

 

Edited with Photoshop to make it more interesting

 

What did you do it? Can you post the max file?

[Hao La]

hi , I tried to render eexterior with mental ray . Here is the file

 

Max File

[bcampbell]

what did you do in photoshop ? may do the same in AE

[d7man2000]

Is this file for Max 7? because I can 't open it.

Can you please make it work for Max 6?

thanks.

[enigma]

Here's my render.

 

I used the Manual for the Indirect illum. rollout for the light. i Made the photon color swatch same as the light color.

 

GI Samples 5000 no radius

GI Volume 1000 no radius

Photon count 100,000

Energy 50,000

Decay .8

 

For the AO pass, i used 16 for my samples, others are default. Then i comp in pshop added slight glows and here it is....the noie is caused by the low samples in the AO shader of the light.increased samples...longer render time...he he he

[Hao La]

ENIGMA : how long did it take ? what lights did you use ?

[enigma]

It took 5 mins for the AO pass and around 10 mins for the GI diffuse pass. i'm running a 3.o ghz p4 proc. I think it's still a long time if its an animation frame but i guess with dual proc. or a multi-cpu setup, its next to a lightning fast frame render. I used only a single mr spot. no FG btw. used AO to simulate FG.