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General => Terragen Discussion => Topic started by: Eric Johannsen on December 30, 2016, 04:22:19 PM

Title: White Dots on TG2 Render
Post by: Eric Johannsen on December 30, 2016, 04:22:19 PM
I'm rendering an OBJ imported from Blender. There are many white spots on edges. What's causing this and how can I avoid them?

I'm using Terragen 2.

(http://puu.sh/t667i/d7a24b338f.jpg)
Title: Re: White Dots on TG2 Render
Post by: Matt on December 30, 2016, 05:24:04 PM
It's probably caused by "Unpremultiply colour" in one or more of your Default Shaders (the unpremultiply options are on the Images tab). If you know which shader is responsible for that part of your object, start there.

Matt
Title: Re: White Dots on TG2 Render
Post by: Eric Johannsen on December 30, 2016, 05:41:36 PM
That did it!

The render doesn't look much different, other than the white dots being gone.

What does unpremultiplied color do? Why is it the default if it can lead to white artifacts?

Thank you for your help.
Title: Re: White Dots on TG2 Render
Post by: penboack on December 30, 2016, 08:04:50 PM
Try this link for an explanation:
http://www.cgdirector.com/quick-tip-straight-alpha-vs-premultiplied-alpha/ (http://www.cgdirector.com/quick-tip-straight-alpha-vs-premultiplied-alpha/)
Title: Re: White Dots on TG2 Render
Post by: bobbystahr on December 30, 2016, 11:02:57 PM
Quote from: penboack on December 30, 2016, 08:04:50 PM
Try this link for an explanation:
http://www.cgdirector.com/quick-tip-straight-alpha-vs-premultiplied-alpha/ (http://www.cgdirector.com/quick-tip-straight-alpha-vs-premultiplied-alpha/)

so is unpremultiplied colour the same as unpremultiplied alpha ? as that's what the page talks about.
Title: Re: White Dots on TG2 Render
Post by: penboack on December 31, 2016, 05:33:07 AM
Yes, same thing.
Title: Re: White Dots on TG2 Render
Post by: bobbystahr on January 01, 2017, 04:16:58 AM
Quote from: penboack on December 31, 2016, 05:33:07 AM
Yes, same thing.


Thanks, confusion lifted.