Hi everyone,

I have searched everywhere for an answer to this question but have yet to find an answer that works with what I am trying.

I’m trying to render some products for a portfolio so when they appear on a white (transparent) background with just shadows.

I am using mental ray with a daylight system.

I have tried using the matte/shadow/reflection material for the ground plane but all I get is a black plane. Using a white plane doesn’t work either as the color is not white under the daylight. It seems to me the matte/shadow technique is the best, I just have no idea how to do it.

Thanks in advance for any advice.

Laptop W/ intel core duo @ 2.8 Ghz, Nvidia GEFORCE GTS 160M, 4 Gigs Mem. Windows Vista
BOXX Render Node W/ 4 QUAD Xeon E5520 @ 2.26 Ghz, 12 Gigs Mem. Windows 7

Here is some tips from Zap using the M\S\R material. But, he did make it easy on himself here by using Standard light, not Photometric ones like mr Daylight. It is possible though, I’ve done it. It just means some messing around with the mr Photographic Exposure Control, namely the Physical Scale setting. Here is Zap’s explanation of that.
Also search the forums for “White Background” or similar, it’s come up a few times before.

Since you haven’t mentioned what version of 3ds Max you’re using, I’ll just have to assume it’s the latest, 3ds Max 2010.  In 2010 you can disable the mrPhotographic Control’s effect on the background and that can be helpful for things like this. 

I’ve attached a simple example scene for deconstructing purposes.  In the scene you’ll find a ground plane, text object, teapot primitive, and the daylight system with photographic exposure control.

The ground plane uses the matte/shadow/reflection material with a transmat shader mapped to the camera mapped background swatch.  This will ensure the shadow plane matches your background by eliminating the surface color without dialing down the mask/opacity value which can remove the shadows completely.

The environment uses the Environment/Background switcher so that you can have that plane white background but still provide something for your objects to reflect other that plane white.  In this scene I used one of the default HDR’s that ships with 3ds Max.

The photographic exposure control uses the unitless physical scale with a value of 95000.  I won’t go into the reasoning on that because it’s thoroughly explained in MasterZap’s blog links above.

Jeff Patton
My Website | mental ray materials & blog

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Jeff, that’s a neat trick putting the Transmat in the Camera Mapped Background. That’s what I was missing when I did the scene in this thread. I had trouble getting the balance between the Physical Scale setting and the EV to get the M\S\R to show white without bleaching the objects. Telling the Exposure not to affect the backgroung worked for the background, but not the white of the M\S\R material.
When I tried to re-create it in Max 2009, I could not get it right.

Thanks Guys,

I think I finally was able to render something without doing too much in photoshop afterward.

Thanks again.

Laptop W/ intel core duo @ 2.8 Ghz, Nvidia GEFORCE GTS 160M, 4 Gigs Mem. Windows Vista
BOXX Render Node W/ 4 QUAD Xeon E5520 @ 2.26 Ghz, 12 Gigs Mem. Windows 7

Good Evening

this shader is really interesting.
But after some test i didn’t find the way to obtain the alpha channel without the “matte/shadow” plane from the render and keep the subject’s alpha and its shadow on the matte/shadows plane.(like the traditional matte/shadow material of scanline render)
This is usefull for compositing

I joined a screenshoot to illustrate my post in case i’m not clear

thank you in advance

Cyrille

I hope this time i m successful. i bring 2 screenshots.
one with the scanline render and the second with the MR shader.
in the first case i can get the alpha channel with shadows but without the shape of plane(which has matte/shadows of max) and the second where the plane is visible on the alpha (with mental ray shader). You understand what gain and benefit are to get an alpha channel clean quickly (in the 1st case).
So how can i get the same with mental ray ? how keep the shadows without the support

I hope i m clear despite my poor english, but i work to progress
i thank a lot to your interest

Cyrille

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Strange,when I use the M/S/R material, it usually shows as transparent in the alpha. Typically when using the material, and certainly if the background is an image rather than a plain colour, as in your screen shot, the Camera Mapped Background slot will contain the Environment/Background Camera Map (mi) shader, which in turn contains the image map in it’s map slot. The shader has an option you can check for “Force Transparent Alpha”, checking that will do it.
See Zap’s Production Shader Examples. I’ve done some simple one of my own in this thread and this thread, with a bit of explanation.

No problems here as well.

ivan

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I got the culprit; when in the M/R/S material there you are having not a switcher but the environment map you get the issue. (See Attachment)

ivan

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THANK YOU

Yes, I have to use “envionmnt/bckground Camera Map” before the picture of background. It’s not easy but it works. I shall never redo the scene twice MR and SL. OUF !
Thank you Samab, Ivan for your help

Cyrille