1
$\begingroup$

Hey there Blender Community,

I am attempting to render just the outline of a fully transparent object on a transparent background (in Cycles). Using a material index pass and an inverse Sobel filter, I am able to produce the outline effect successfully on a white background. See below:

Functioning Object Outline on White Background

However, when I make the film (the background) transparent, the outline disappears. Is there a way to keep the black outline of the fully transparent object on an a transparent background?

The same node setup, but with film set to transparent:

Nonfunctional Object Outline on Transparent Background

My thanks in advance for any assistance or pointers in the right direction.

Improve this question
$\endgroup$

1 Answer 1

Reset to default
1
$\begingroup$

Not the most elegant solution, and probably there is a better one, but if I understand correctly maybe this will help:

enter image description here

click to enlarge

Using a Color Key node to replace the white with transparent pixels, and adding the key to the image seems to work well in this case.

Improve this answer
$\endgroup$
3
  • 1
    $\begingroup$ This worked beautifully for me. (And I'd say that adding only one node is a pretty elegant solution.) Thanks very much! @Timaroberts $\endgroup$ Commented Jan 23, 2018 at 19:37
  • $\begingroup$ @ColinConwell, you're welcome. Glad to help. $\endgroup$ Commented Jan 23, 2018 at 21:42
  • $\begingroup$ One question: Would it possible to somehow animate this? Such that the color drained out over some number of frames? $\endgroup$ Commented Jan 23, 2018 at 22:14

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.