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Junior Member
 
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Last Login: Wednesday, May 16, 2012 12:19 AM
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| Hi guys, I was wondering how everyone deals with alpha channels and the white halos you can get, especially with trees when you want to substitute a different sky in an image. Is there a particular file format that helps get rid of this problem ? I tend to use tiff's. The best of a bad bunch solution I use is importing the tiff into After Effects, selecting 'straight' rather than 'premultiply'. This helps but it's still not a perfect cure and then I still have to muck around with the image in Photoshop with a combination of layer defringing and burn. Anyone got any other ideas / methods ? Cheers,
Colin
------------------------------------------Colin Hanford
Senior Visualisation Designer
Arup
http://www.arup.com
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Veteran
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Last Login: Thursday, May 03, 2012 8:59 PM
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Are you referring to rendered plates or textures in MAX? If it's rendered plates from max, if you're planning on replacing the sky, render with a black background. PNGs give you a good premultiplied alpha, but if it's a last-minute change, EXRs will give you the best mask and the most opportunity to fix problems (you can use 16 bpp EXRs (half-float) to save disk space 99% of the time). If ti's a texture thing, it's totally in photoshop. http://help.adobe.com/en_US/Photoshop/11.0/WS1B81490D-0B73-4086-BC65-8ABD4E77D573.html should give you some ideas about both problems actually.
--Tom
THOMAS SHANNON
SENIOR DESIGN VISUALIZATION SPECIALIST
PB Project Visualization
http://www.pbprojectviz.com/
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Junior Member
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Last Login: Wednesday, May 16, 2012 12:19 AM
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| Thank's for the reply Tom, I was on about rendered images with a vraysun or mental ray daylight system where they have their own sky in the environment map of the Environment settings. I have used PNG's in the past but still no joy. I read somewhere the problem was the 'premultiplied' bit and that 'straight' get less problems, hence why I was using After Effects as it gives you the choice, while Photoshop doesn't. I'll have a play with EXR's and see how I get on. Cheers,
Colin
------------------------------------------Colin Hanford
Senior Visualisation Designer
Arup
http://www.arup.com
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The real trick is rendering to a black background. Even EXRs will have a ghosted outline. A pre-multiplied alpha is simlpy an alpha set against a single color (Hence why After effects lets you chose the color).
THOMAS SHANNON
SENIOR DESIGN VISUALIZATION SPECIALIST
PB Project Visualization
http://www.pbprojectviz.com/
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| If you're using a vray set-up, you can put the vray sky from the enviroment slot into the GI slot in the VRay->Environment roll-out, then put the background map you want to use into the regular Max Environment Map slot (I'm guessing MentalRay can do something similar, but don't know for sure) This will make Vray use the sun and sky for GI (via override), but the output image will use the map in the environment slot for picking up the alpha color around the edges. I use this technique for photsims and it avoids the bright/white halos. I put the background image/photo in the Enviroment slot set to screen mapping. You may have to adjust the output of the image depending on the gamma and camera settings, but just getting it close is fine since you just need a few pixels of the background colors 'burned' into the halo, then comp with the original in photoshop. SJ
Steve JohnsonPBProject Visualization Technical Resource CenterE-Mail: johnsonste@pbworld.com...................................................................................................
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Junior Member
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Steve, I can't thank you enough. Your method in Vray works an absolute treat, it's brilliant. Genius!
------------------------------------------Colin Hanford
Senior Visualisation Designer
Arup
http://www.arup.com
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Veteran
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Last Login: Thursday, May 03, 2012 8:59 PM
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Yeah, Steve, thanks for breaking that down. I've been out of Vray practice for too long now.
THOMAS SHANNON
SENIOR DESIGN VISUALIZATION SPECIALIST
PB Project Visualization
http://www.pbprojectviz.com/
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Newbie
Group: Forum Members
Last Login: Friday, July 22, 2011 10:16 AM
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i am new in animation feild learning 3ds max 9.and unable to understand the course.iwant to learn the full course with every funda of animation & modeling if u have any tips and helpful resourse please helpme through mail my email id is ( shaikh.zoyeb@yahoo.co.in)
shaikh
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Newbie
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Last Login: Monday, September 26, 2011 4:39 AM
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Have a look at the site:
http://www.lynda.com/3ds-Max-9-tutorials/essential-training/287-2.html
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