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poly enslaver
04-08-2004, 03:45 PM
Hi there. I saw many threads about rendering interiors with MR for Maya but as my internet connection isn't permanent and I can only SEE I've decided to ask you all guys about my light problem!

I was looking at the illumination of my room and I realized that as the sun's ray (direct) don't hit my room however it's bright with these soft shadows! How can I simulate it in MR? What's better big part of white bright sphere as Fg source or maybe area light source? Maybe light shaders? Any ideas. Pleas help!

poly enslaver
04-08-2004, 07:54 PM
Strange... Noone can help me? Here are so many MR masters, where are you?

andrewjohn81
04-09-2004, 04:03 PM
You should realy describe the situation more clearly. Is the light comming through a window in which you wish to get the shadows from? Are you using global illumination?

Most of the time, the problem that arises is due to final gather. There are some hidden attributes if you are not using Maya 5.1. After opening the render globals and choosing mental ray it creates a node called midefault options or something like that. You can find it in the outliner when you make sure "show DAG objects only" is not checked. If you select it and open the attribute editor you will see the hidden attributes under the extra tab at the bottom. Turn Final Gather filter to 0 and there are options also that look similar to Ray trace options which count the number of bounced or refracted light from FG rays.
The default is very low. If you plan on moving light from FG through a window then you would need to change these numbers to accomodate that. If the window is has thickness then make sure the refracted rays are at least 3 so that the ray will pass through the window.

I couldn't tell your actual problem based on the descreption you listed, I just took a wild stab in the air. It might help to give the attributes of you lights that are giving you problems, give a more details description of your scene, or show an example image of what's happening.

Sorry I couldn't be of more help.

poly enslaver
04-09-2004, 10:50 PM
Hi! THX A LOT! A appreciate it very much! Now I'll try to decribe it more clearly.

So I have only one window in the room that I wish to be lit thru that window with diffuse light. Not like the sun rays are falling straight into my room.. I want to achieve effect of blured shadows from objects and also the room should ve lit at all. First I used only one area light with GI photons. It has sizes like the window room... the shadow are pretty nice and if the Gi is in the room is also good lit. But we all know tha the first stage photons are not stored they are only reflected, so there is some artifacts on my objects, I mean some of their parts are very bright and some are so dark! I thought that was because of GI number of photons so I set it to 1000000 photons. But anyway these dark spots are still present, even radius of 0 and accuracy of 20000 don't help.

I speak too much, but really want to learn that situation. Maybe I should turn off photons for that window light and create another light, that only emmits photons in different directions and the all are passing thru the window, and I think these photons when the are coming thru window should be reflcted at this moment. ???

BTW waht about best GI values settings? Does it make any difference to MR if I am using meters units or centimeters? I used to set radius to 0 and accuracy to the biggest value that MR could set, but in that case I need at least 1000000 photons!!!

Maybe I should post that small scene if somebody is interested in making real physical day diffuse light! Thx in advance

Emmortal1
04-09-2004, 10:54 PM
When using GI, HDRI, or FG you'll always want to lower the Irradiance color values to .314 .314 .314 respectively. By default it is at 1 which is incorrect. You'll also want to attach photon shaders to the shading groups as well to control the photons on those objects. If you are getting color splotches from reflective or refractive objects in the scene on your walls or other objects, then you'll want to lower the diffuse value for those objects and that should get rid of those.

poly enslaver
04-09-2004, 11:16 PM
Yeah thx I knew that. In this case I jsut use one dgs material as Mi material and also dgs as photon material... I haven't even turned FG, so as I am using DGS shaders and any other maya shaders are suppreseed i think the solution hides somewhere else.

Thx again for replying Emmortal1.

Emmortal1
04-09-2004, 11:20 PM
Not a problem, just wanted to make sure that was covered. Your GI accuracy settings could also be the culprit of photon artifacts as well, might want to take a look at that.

Gremlin
04-09-2004, 11:24 PM
ive never gotten GI to work the way i really wanted it to, but i didn't mess with it too much. the render times take a bit too long for me to really be able to tweak the settings...

thus, i can't wait till Maya 6 cause i heard it'll have IPR available for mental ray renders! :D

jeremybirn
04-10-2004, 02:12 AM
Your photons will always be a bit blotchy until you turn on FG - FG smooths them out. If I ever had to use just one (GI or FG) by itself, I'd start with FG. Radius of 0 is good, that auto-sizes the radius. But don't use toot many photons or too high a quality, it'll take forever and won't make-up for the lack of FG.

If you want the photons to travel further give them a lower exponent instead of 2.0.

Start with simpler Maya shaders (like lambert, PhongE) if it's your first time through - don't give yourself too much to worry about at once!

-jeremy

poly enslaver
04-10-2004, 05:09 AM
Hm.. So you guys really think FG should be ON, right? Yeah I hope so, but it takes a long time... How many Fg rays should I set? And btw how should I place it? Enviroment color of a camera (high value maybe 6-9), or some part of a dome just covering a window? I know the first one renders too long.

[you know guys I 've looked thru many threads of CGtalk (maya of course), but as my internet connection isn't permanent and speed is amazingg low (3,5 kb/s) maybe I missed something, or I should not just read but also discuss?]

If we are talking now may I ask ypu one very important question?At this moment my PC is lying down on the table in different parts.. because I upgraded it!!! From 1800 celeron 128 L2, 512 ddr 266 to 2800 prescott 1024 L2 800 mhz bus, 512 ddr 400 2-channels. I tested it in Maya, you all know that there are 2 processors (hyper threading) and I wanted to ask about performance.. Old PC- 31 minutes 21 seconds it was rendering, and New configuration 13 minutes 23 seconds. Is that normal? Should it be fasted jr maybe that's cool enough? I saw many times something like this 2x1800 amd or 4x2000 amd, should I try something like that? Maybe someone can post a link for such tests? that will be really cool for me! Thx you all guys!!! (sorry for this big amount of qestions, I wasn't talking too much so long :-))

Gremlin
04-11-2004, 02:06 AM
FG should be on, but with very minimal rays, I think around 300 (but it depends on the scene, plus i'm not that knowledgable about MR renders) :surprised

Undseth
04-11-2004, 02:39 AM
About the number of FG rays (with FG rendering only!);
Just wanted to mention that I usually get away with 600-1200 FG rays, but with a recent rendering, I had to push FG rays up to 6000 to get a "noiseless" FG rendering (I was a bit puzzled over that).

But I guess that was for a reason, I just don't know why. Maybe it was because my model was a bit bigger than usual (about 75 units/d). Usually my model is only 20 units in diameter.

The rendering seemed to become more noisy when I lowered the Min-/Max-rad values. I needed the low settings, so I had to heigthen the FG ray count.

Btw; I'm a mental ray newbie.

Undseth
04-11-2004, 02:54 AM
Sorry, upon reading everything in this thread I see that the knowledge level is some place higher than mine :D, so forgive my former inane post.

However, I dare intrude and ask about something:

Poly Enslaver: "But we all know that the first stage photons are not stored they are only reflected, so(...) "

I notice that a GI rendering of mine shows some horrible bright spots, where the photons seem to hit directly and reflect from one surface (say a floor) to another (say the lower part of a wall)(and vice verca).

Does "this" have anything to do with what Poly Enslaver wrote (quote above) or have I perhaps misunderstood?

OR

What did Poly Enslaver mean by this: "But we all know that the first stage photons are not stored they are only reflected, so(...) "

poly enslaver
04-11-2004, 07:42 AM
Hi. Undseth everyrhing is ok. I'll try to describe what did I mean and how I've solved it. Btw I am not so good in english so perhaps maybe my post is nonsensial... however let's move on:

Look if you read some docs about MR photons map will find that photons first photon is emmited from the light source hit's the something and is reflected but NOT stored. So If you try to illuminate your plane only with photons (intensity of a light is 0) you won't see nothing even if that's plane is diffuse. So in my case I used one light to create sharp shadows (without pghotons) and light only with photons for simulating the diffuse illumination. I've got to bright walls and ceiling but not the floor and i haven't got any diffuse blured shadows... And then I created big area light (plane) and turned On shadows and photons now I' ve got diffuse room illumintaion and also can add sunS direct one. And now after reading all these posts of yours guys (THX A LOT ) I am going to turn ON even FG. But which way? Just ON? or maybe part of a dome?:)

poly enslaver
04-16-2004, 03:28 PM
help me... I can't get really nice look of my textures, don't know why! I am using nice photo textures but when I render final picture I get smooth result... I know it depends on filter type and size but, if I set triangle I get these jagged edges... maybe I should use Lancoz?

anthonymcgrath
10-18-2005, 10:06 AM
Your photons will always be a bit blotchy until you turn on FG - FG smooths them out. If I ever had to use just one (GI or FG) by itself, I'd start with FG. Radius of 0 is good, that auto-sizes the radius. But don't use toot many photons or too high a quality, it'll take forever and won't make-up for the lack of FG.

If you want the photons to travel further give them a lower exponent instead of 2.0.

Start with simpler Maya shaders (like lambert, PhongE) if it's your first time through - don't give yourself too much to worry about at once!

-jeremy


hi Jeremy,
I was reading thru this thread - I'm trying to get a car headlamp to emit some light from the object and i'm using a method you mentioned elsewhere about duping the object, assigning a super bright (V value above 1 - something like 100!) and turning off primary visibility for the object so only trace results are rendered out. in the bit above you say turn the exponent down for photons to travel further but I cant see that option in maya6 for my shader (basic lambert) - the only way to control my bounce colour is to crunk up the V value up or down.
those irradiance colour swatches are useless too - they make no contribution to the object bounce light whatsoever :/

You also mention too many photons wont make up for the lack of FG - do you mean GI in this sentence?

if anyone else can 'shed any light' on this matter that'd be cool :)

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