Texture alpha question

Texture alpha question

Sorry if this is a redundant question, but I searched the forums for an answer and I am still a bit lost regarding using alpha channels in a texture. Please see the attached images. Basically I have a tiff texture with an alpha channel that knocks out the "blank" part of the image around the red squiggle. I create a material, use this tiff image as the texture map and set "use alpha channel" in the transparency section. In the 3D view, it looks exactly as I want it (the geometry is a simple plane on the right and a plane "shelled" out on the left). But when I render, I cannot get a similar result. I have tried many combinations of texture "color" and transparency "color", but all results are similar variations of this. Any help would be greatly appreciated!!

PS: the green color in the render is camera background color only

Thanks to all!
 

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Hi,

You need to put a background in your scene (behind your plane), otherwise the renderer just see the "black cyberspace".
I hope this helps.
 
I had the same problem - Cheetah's renderer doesn't yet support transparency with background colours/images. It's a bit of a pain if you want to use the alpha channel as a mask in Photoshop etc... but I found you can work around it using a difference matte.
 
Hi karloc, Hi squareitround.
There is a simple workaround for this. Render your scene within a globe textured with a solid color. Because you want to make a montage, you have to take your render to your bitmapeditor one way or another and make the background/solid color to alpha - that´s it.

With kindest regards
Frank
 
Re: Texture alpha question

Thanks everyone for the quick and helpful replies! I re-tried with the globe as suggested by Frank and it worked perfectly. Now my only question is how to combine this magic globe with an HDRI background ;) But that gives me a good task for this student to try!

Thanks again!
 
Hi karlok.
Ok, for the hdri renderthing we need trick n°2. You can put a solid color plane opposite your camera, far far away and big enough to fill your cameraview.

Be aware: For just cutting out your model it´s a smart way. On the other hand, how would you explain the beautiful reflections in a montage against a different background? ;-)

With kindest regards
Frank
 
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