Lighting : Mental ray and Interiors


#1

Ok well here is the situation. And Currently attempting to build an interior using max 6. But I cant seem to get the lighting right. I have the following:

1x Room and Window with Glass(pf) on the pains.
1x External mr Area / Omni Light
- Multiplier 1
- Pretty much standard stuff.
1x Interior light same as above

MR Global Illumination Settings:
- Photons: 500
- Samples: 10000

Final Gather:
- Sample: 1000

My main aim is to get the look and feel of it being a bright day outside. But its currently quite dim and unrealistic. I have played with the exposure controll settings but still seems off.

Could any one suggest how I should go about lighting this scene with mental ray. I know I can do it with radiosity, and light tracing and I have, but I am trying to get my teeth into mental ray.

I am also going to convert this whole process into a tutorial so other people can learn from this whole indaba.

THanks


#2

Hi,

I think you should increase energy multiplier for every light (under MR indirect illumination rollout), rise 10, 20 or 50 times until GI will show up in renderings.
Do not bother with samples under Photons rolout under “Volume:” as it goes only to volumetrics.
Use final gather with max radius and preview (no precalculations) turned on and samples about 50-100, this will give you fast and quality previews about the illumination for test renders.

This is what I got only with one MR area spotlight on quick test:


#3

I allways put a very big and slightly blue MR area omni in front of every window to simulate the sky light
then use a white-yellow MR area spot light for the sun
never use lights inside (except for decoration light fixtures on walls and sealings, but they never light up the entire scene anyways in daytime setups).

forget about using glass in your windows at first (it’s very hard and rendertime consuming to get light going through glass in MentalRay and have a nice lit interior, i allways composite a scan line glass in the windows afterwards)

first make sure you have your units correct :
a ‘cm’ in your units should represant a cm in real life
this is very important to get your sample size under control

I always start with only a few (2500) GI samples and make them 30-60 cm
make sure you can see the photons on your scene objects (kinda like a flash light shining on a wall)
if you can’t see them then there’s something wrong with the units

once you see them ok, turn on final gather very low (lets say 50)
just to have a quick preview on a 320/240 test render
(should only take a few mins)

to brighten up your scene don’t mess to much with the multipliers!
play around with the energy level (20000-100000 should do) and together with that : decrease the decay (from default setting 2.0 to let’s say 1.6)
just enough to brighten up everything in the scene and have more bounce of the light away from the windows
in my experience it’s a very sensitive parameter, cause when to low (let’s say 1.5-1.1) could make the render go completly white and overlit…

then when satisfied with the result only increase the image size and Fgather untill good result.

tip : :lightbulb when you really can’t find a good setup there’s a very good example scene that come’s with the official max6 install package from the guy’s from KDLAB. Import your scene in that file and that should get you going
:beer:

here’s a sample of what I got out of Mental ray so far :


#4

Joske,

Thank you very much for the tips. I have a building I’ve extruded from CAD files and I’m having a hell of a time getting a nice lighting setup. I’m going digging through my MAX CD’s for that scene you were referring to.

Any tips for lighting a large floor plan? The whole exterior of this floor plan is glass. So how would you light the interior rooms that do not have exterior windows? Regular lights, photometric or what?

I can post the file if you want to have a look at the building and offer ideas.

Thanks again,

Jeff

EDIT: Sorry I didn’t mean to sound like I’m hijacking this thread.


#5

Thanks very much all your help is much appreciated. I am going to apply what you ppl have said on my current wip. Thanks again.

EDIT: No worries about the Hi jack, I am looking forward to seeing your building.


#6

Originally posted by folical9
[B]
Any tips for lighting a large floor plan? The whole exterior of this floor plan is glass. So how would you light the interior rooms that do not have exterior windows? Regular lights, photometric or what?

I can post the file if you want to have a look at the building and offer ideas.

Thanks again,

Jeff
[/B]

Jeff, keep in mind that there’s no setup that will fit every interior scene, once you’re familiar with the settings and parameters from MR, there’s no telling what you’ll end up with in the end…
Just hardworking trial and error untill you get it wright :hmm:

My rule of thumb would be to make the lightning like in reality.
An office room with no windows will probably have a door. Open it to get the sky and sun light from the next room, mabey it’s not much, but there allways will be some light. Lower the decay untill you get some light in (in my exp it will give more bounce). In reality there’ll probably be a neon sealing light. So put a MR spot or omni (whatever tickles your fancy) with an area shape of a neon light.

And… i allready used your DIRT shader to mix in post with my final interior image. When I get to the office i’ll post you an example :wink:
I found out that the size of the scene is very important to get a good effect (when i left the scene in 1 cm = 1cm i had allmost no dirt at all, scaled it down like 1000 times and voila… instant succes :eek:

sorry for going a little of topic here… mabey we should start another thread like the ass kicking ‘mental ray shader’ thread from folical, but this time to share interior lightning tips and tricks… :drool:

later dudes


#7

Hey the lighting thread with mental ray would be a big help.

Check this thread out for what I am busy with

WIP: My Room

Thanks again for all the help. Just one question about the Omni Area light and the spot. I have placed them in my scene, which is 1cm = 1cm, And it doesn’t look bad but still feels wrong. (See above link)

Thanks Again


#8

Originally posted by joske
[B]I allways put a very big and slightly blue MR area omni in front of every window to simulate the sky light
then use a white-yellow MR area spot light for the sun
never use lights inside (except for decoration light fixtures on walls and sealings, but they never light up the entire scene anyways in daytime setups).

to brighten up your scene don’t mess to much with the multipliers!
play around with the energy level (20000-100000 should do) and together with that : decrease the decay (from default setting 2.0 to let’s say 1.6)
just enough to brighten up everything in the scene and have more bounce of the light away from the windows
in my experience it’s a very sensitive parameter, cause when to low (let’s say 1.5-1.1) could make the render go completly white and overlit… [/B]

Great idea about the omni simulating the sky light. :slight_smile:
I often try to assist GI or Radiosity with lights inside, because although every raytracer claims its solution is physically correct, there are too much factors in real life that we miss in a scene. I dont rely only GI sollution. The attached image uses two area lights: one for window and one for simulate bounced light.

As I understand the decay setting is power of light energy decay over distance. If it is 2 then light diminishes in inverse square decay. Thats why your scene gets overlit when it is close to 1 (then it is only inverse decay). You can even use decay 0, but then you should reduce overal energy to something like 5 or 10.

my old light-study image:


#9

Every scene is unique…but generally how many final gathering samples you guys have had to use to get decent, blotch-free, interiors? way over 1000?


#10

ok here’s the dirt sample
FG settings between 1000 - 3000 for final renders not more…


#11

the version with only the GI setup


#12

and the mixed version with the dirt
by the way i hate the red colors and the green door, the architect chose them not me :rolleyes:


#13

Thanks again for the tips guys. I’m attaching two renders I have thus far. I have to create these type floor plans frequently now, so I need a solid solution on the lighting so my work looks consistant.

This one uses only one skylight and final gather. I think this may be the way to go. I suppose I should turn down the skylight and add some soft omni lights into the rooms to make them a bit brighter (especially the interior rooms)?

In this one I setup a BUNCH of omni lights (like 4 per room). And adjusted the decay of the lights to overlap each other. This one renders quicker than the skylight version above. However I like the shadows better on the one above (skylight). I forgot about the dirtmap shader…I’ll give that a try too.

If you guys have any other ideas for lighting these floor’s please let me know.

Thanks again,

Jeff


#14

bump

Any ideas on how I should properly light the floor plan above?


#15

I like more the one made with omni lights. It looks much smoother and has more cartoonish style which is more acceptable for visualization like this one.
to me only a few things you could adjust. I dont like black areas where iside walls are. these could be capped and illuminated to not contrast with whole image (or just make like sky light image). Windows could be more transparent and reflect.

Sorry didn’t sugest any illumination tips, but I like illumination made with omni lights :thumbsup:


#16

folical: I would go for a very stylish “clean” approach. That could be a cartoon/drawing style (maybe using Ink’n’ Paint). I would avoid shadows from multiple sources and go for an evenly lite scene, using a dirt map only for the floor, putting some lights or self illumination in the windows (or just a brighter material) and brighten the shadow parts of the rooms.

But that is a matter of taste and what style your are after.

Boa


#17

Thanks for the tips. I have not tried illuminating the windows, good idea will give that a go and see what happens. I am looking for a uniform lighting appearance. Very subtle shadows and an even light amount. The main focus will be on the ductwork and hvac parts above the floor plan. However, I want the floor plan to look great as well.

Again, thanks for the input!

Jeff


#18

Hello to all!

First of all i want say thanks for very helpful thread about lighting in MR.

Today i be confronted with difficulties which you can see on picture.

How i can escape from this smoothed colors?

Sorry for my english/


#19

try to use higher sample rate for your omni near the window
if that doesn’t work try higher fgather settings
if that doesn’t work try smaller GI photon radius combined with more photons

keep in mind all above will increas the rendertime alot
so it’s a trade off between smoothness - rendertime

tip :if you wanna have transparant shadow of the glass table you will have to use caustics as well, however untill now i didn’t see anyone pull that one off… (me included he :wink: )

good luck with it

phil


#20

Thank’s Joske you really The MAN. I try use that. Later put here my results.

Originally posted by joske
tip :if you wanna have transparant shadow of the glass table you will have to use caustics as well, however untill now i didn’t see anyone pull that one off… (me included he :wink: )

Thanks too :), but i knew that. Simply above all i tried illuminate my scene and just put material on table for no particular reason.

PS. Sorry for offtop. Do you know how i can get effect of matt glass?