View Full Version : Simple nodal surfacing question: masks and alpha channels --noob level

08-07-2016, 11:04 PM
Working on a simple surface, see jpg:

(I've disconnected some of the nodes in this image, since it wasn't working, but left the nodes themselves in so you can see what I was playing around with.)

The idea here is that the image defines a gravel path. My trouble is getting a gray, nobbly surface into the exactly same area as the black stripe on the bitmap, without affecting the brown Background color of the Hybrid Multifractal node.

I thought that I'd have to use the Image Node in two applications, one as a negative mask for the ground surface, the other as a positive (inverted) mask for the gravel texture, but I can't seem to find a way to wire them together that does that, and in typing that down I have the feeling I'm somehow overthinking this.

Anyway, any help is appreciated: I think it's some fairly simple thing.


08-08-2016, 12:32 AM
Here we go... (ed: or at least a step in the right direction...)

Actually, that didn't work as cleanly as hoped: note the color cast in the path-- the mask image is purely b/w, but a little of one color (green) seems to be bleeding thru the mixer.
Additionally, note 'missing pixels' in the gravel path: the original mask image should be straight black there, but there are pixel voids. I turned off MIPmapping in case it was screwing up the purity of the mask but it didn't seem to matter

(btw, note how I add to posts instead of adding dozens more....) :grumpy:

A LW user over on FB kindly pointed out that the OPACITY input was the one to use on the Mixer node, not the Blending input, which is a logic input that switches blending modes.

So! Working now. Huzzah!

08-08-2016, 04:27 AM
Use a material mixer node and plug your alpha int the material mixer alpha input

08-08-2016, 09:43 AM
Yup. Sorted.