Compositor doesn't affect Alpha plane

Question

In this render, the butterfly is an Image imported as plane with Alpha. The non-transparent parts of the image have an Emission material with 18 Strength.

The Sphere above the butterfly has Emission material with 18 Strength.

However, once composited, the Glare effect from the Compositor seems to only work on the Sphere and not on the Alpha PNG.

How can I change my Node setup so that the Image-Plane also be taken into consideration by the Compositor?

score 2 · Accepted Answer · answered Feb 13 '18 at 00:53

2

I think the short answer is that the image plane is indeed being taken into consideration. I checked that by altering the colors of your image so that the butterfly is white instead of pink. In this case, the glare node does affect the butterfly.

I think your best bet is to really crank up the strength of the emission shader for your butterfly (I tried 200), which will give you the glare. If you want more control over the color of the butterfly image itself, you could experiment with render layers--use one layer for the butterfly image to be "glared", another layer for the color to be composited over top.

answered Feb 13 '18 at 00:53

risingfall

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So in the image you are posting, you just cranked to 200 the plane emission? I was under the impression that the Mix Shader was not making the Emission value smaller by dividing it, but maybe I was wrong? – MicroMachine Feb 13 '18 at 00:56
When I opened your file, you had your butterfly plane material's "Emission" component at 18.2. I changed that value to 200. The mix shader (as you have it set up) is simply making part of your plane transparent, it is not touching your emission values in any way. My point is that the glare node seems to create glare around colors that tend towards white, the pink color you chose for your butterfly is not white enough to get a noticeable glare effect. – risingfall Feb 13 '18 at 01:03
@MicroMachine read: https://blender.stackexchange.com/questions/54168/any-way-to-control-light-halos-in-the-compositor-based-on-emission-level/54173#54173 – Feb 13 '18 at 16:49

score 1 · Answer 2 · answered Feb 13 '18 at 08:15

Option 1: Change the Threshold

The glare node checks pixel values. And only take into consideration pixel values that are higher than the Treshold value of the glare node.

Bumping the Threshold to a low value the pixels of the image are also taken into consideration. Between the values 0.1 and 0.4 the image of the butterfly are also taken into consideration.

Option 2: Extract background for even more control

In order to really not influence the background it is better to first mask it Extract it, calculate the glow and add the glow to the original image.

Compositor doesn't affect Alpha plane

2 Answers2