Window / Glass (box) - GI, light and shadow

[Marco Tomaselli]

hi there...

i made a scene....

and the window (BOX ,NOT PLANE) with the glass shader, it´s not generating GI in the room...and others shaders are not generating shadows in the room too....because the glass shader don´t work very well....i don´t know...

what´s the "right" glass shader to mr?

thanks!

[luckymutt]

Which glass shader?
Glass(Physics-Phen)?
or a mental ray material with a "Glass(Lume)" shader in the Surface slot?
If it is the second, make sure to put a "Photon Basic(Base)" shader in the Photon slot under Caustics and GI.

[Marco Tomaselli]

i tried many types....

and in the glass (lume) i used photon basic...in the photon slot....


but don´t generating GI...only without "window".

[luckymutt]

I usually use a mental ray material, Glass(Lume) in diffuse and Photon Basic(Base) in the photon slot.
In the Photon Basic parameters, the Transparency level is black by default, so you need to change it to white to allow photons to pass through.
Other than that, it's a matter of cranking up your GI.
I dunno about anyone else, but I never use the "Automatically Calculate..." option in a light's rollout.
I always set it manually for each light.

The problem I wind up with is that even though light is still coming in and bouncing properly, I don't get much of the dirrect light hitting the initial surface the way it should.
Glass does cast a shadow, so you need to turn on Caustics to get a nice transparent shadow from the glass, but even still, I can never seem to get ti to look proper.

Using the Glass(Physics_Phen) material does seem to handle hitting that first surface the way i'd like it too, but again, Caustics must be enabled.

If you want I'll post a scene showing a way to do it.

[luckymutt]

Actually, I am going to go ahead and post these for clarity.
This should be a good starting point; however, I am no expert so perhaps someone else can spot if I am not doing something incorrectly/inefficiently.

Please note: this is just set up as a simple test and is not intended to look pretty. I took no steps to make the GI smooth and accurate, but rather just threw it in there to see how the Glass materials were working.

Here is the simple scene
(http://www.bei-media.com/postings/mrGlassWindowTest.max)

The scene is to scale, and the window glass is 3'x4'x0.25" and is centered in the window opening.
The only difference between these two renderings is the material.
http://www.bei-media.com/postings/glass_phys_phen_Caus.jpg
http://www.bei-media.com/postings/glass_mrmat_glasslume_phbase_Caus.jpg
http://www.bei-media.com/postings/mrGlass_settings.jpg

[Marco Tomaselli]

hey luckymutt, thanks man...

but listen that...

after that i realize one thing...

the MR SUN is the problem....

because this light is photometric i guess...only with caustics works...

please test this too...

regards

[SERRGEI YOSSARIAN]

HI
FIRST
SORRY FOR MY ENGLISH IS POOR LOL
I SEE THIS Thread AND I SAW WHICH MY PROBLEM IT'S SIMILAR. IN THE NEXT IMAGE THE SHADOWS OF THE GLASSES I DONT LIKE ME IN PLACE OF SHADOWS I WANT A SIMILAR EFECTS TO CAUSTIC BUT I DON'T WANNA CAUSTICS, BECAUSE THE CALCULATE TIME ASCEND IT.
I'M USE A GLASS LUME SHADER, AN ONE MRAREAOMNI LIGHT, ONE SPOT LIGHT,ONE OMNI LIGHT AND SKY LIGHT,
FG 10 SAMPLES MAX RADIO 2000 MIN RADIO 1000 & GI 100 SAMPLES 1000 PHOTONS.UNITS CM SCENE REAL SCALE ANDA GLARE OUTPUT SHADER.
ONLY WANNA TRANSLUSCENT COLOR SHADOWS.

THE QUESTION IS
SOMETHING KNOW A SHADER GLASS WITH THAT CARACTERISTIQUE?
SOMETHING KNOW HOW DO IT THAT?

MANY THANX FOR ALL
PLEASE RESPONSE ME I,M STAY CRY FOR THAT
NOTE:THE SCENE IS NOT MINE IT'S EVERMOTION MODELS THE ILLUMINATION TEST IT'S MY TEST.

http://img411.imageshack.us/img411/5476/mentalrayasvray800x6001zb6.jpg

[hoppergrass]

I hide the glass to when generating the GI FG solution, then I unhide the glass and rerender with a frozen GI FG solution.

JHV

[SERRGEI YOSSARIAN]

I hide the glass to when generating the GI FG solution, then I unhide the glass and rerender with a frozen GI FG solution.

JHV
HI HOPPERGRASS!

OK THANX I' LL TRY IT

BUT ANOTHER SOLUTION NO THERE IS?

I WANNA MAKE ONLY ONE RENDER PASS NO FG&GI
SOLUTION ONLY RENDER ONE TIME.

AND SOMEONE AGREE ANY COMMENT FOR MY IMAGE PLEASE THANX FOR ALL

[luckymutt]

To get Global Illumination, you will need wither GI or FG, or both with mental ray.
The only other option is to fake it by putting more lights in your scene set at low intensities, but the set up to get it looking even a little bit close to good will be much more than calculating FG and GI.
Here is an example:
http://www.3dkingdom.org/modules.php?op=modload&name=News&file=article&sid=522&mode=thread&order=0&thold=0

However, I don't think that way will work proper with the Glass shaders...I don't think light will pass through in a way that looks decent without caustics.

[hoppergrass]

By generating the FG pass at a lower res (eg half of the final res) and then rerendering at full res will frozen solution actually results in a faster total render time. Also negates the need to play with shaders.

If you are totally set on doing one render then place some free area lights in front of the glass inside the room.

JHV

[SERRGEI YOSSARIAN]

Hi Hoppergrass Thanx Stay Try It Calculate The Fg And Gi Map In Low Res Next To Be Post The Image,

My Idea Is The Minimum Time Rendering For A Animation
Caustics Elevate The Time Rendering

[hoppergrass]

If you are doing an animation, and the only thing moving is the camera, then render every 10th frame at low resolution, with the glass (and anything else that wont directly influence the lighhting such as clutter objects) hidden.

Freeze the solution and turn everything back on.

Rerender at full resolution.

This method eliminates any flickering and is very quick to render.

If there are objects moving then you will either have to decide to render every frame for the FG calculation or do some compositing.

JHV