alpha channel boundaries are wite

Corona Corona for Cinema 4D General
1

Hi everyone!

I have some issue with alpha channel. After I cutout the background i get white outline around my trees. Is it possible to fix this problem?

tree1_black background.jpg
tree1_black background.jpg1280×720 70.1 KB

tree_png.jpg
tree_png.jpg1280×720 90.6 KB

tree_alpha.jpg
tree_alpha.jpg1280×720 92.8 KB

tree1.jpg
tree1.jpg1280×720 124 KB

2

Hi there, What’s your process of cutting them out? Are you using Photoshop? There are ways to fix this but knowing how it was done would fine tune my answer. Thanks

For now, you could review this:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000653557-objects-with-opacity-maps-are-becoming-gray-when-they-are-far-away-from-camera-

3

I just copy paste the alpha channel in to the layer mask, that’s all. Also, I tried to adjust alpha image with levels or curves, but after that it looks worst. Even if I import png image without background in to the photoshop, I get the same result. It looks like tree leaves reflects bright color from the sky and the alpha channel cuts the object boundaries but doesn’t evaluate its burnout edges.

4

Photoshop kinda sucks when it comes to alpha. My first approach would be using the defringe setting in Photoshop to clean up the edges. If you want, I’m more than happy to look at your file. We have a private uploader that is linked in my signature below. :wink:

defringe.jpg
defringe.jpg531×970 115 KB

5

Seems like exactly the things I was talking about in this post:
https://forum.corona-renderer.com/ Corona masks RGB no clean edges why? #msg115961
and here
https://forum.corona-renderer.com/ Corona masks RGB no clean edges why? #msg115973

And it seems no one knows or uses the solution with tga pre-multiplied which fixes the white outlines.

(but not sure if the trick with “pre-multiplied” would work in Photoshop, or just in after effects)