Setting the texture's grayscale as alpha?

Question

I have the following texture:

I am trying to make a a fading transparency on the part that is black, i could apply this in 3ds max with the "Alpha as gray" option, but i can't seem to do that in blender.

In theory, if i get the material right, it should be basically transaprent in the middle, and blue on the top and bottom, if that makes any sense.

I've been trying playing around with several nodes, with mix and color clamps, but i can't seem to get it right, any suggestions?

Answer 1

Here is the way I would do what I think you're asking. I plugged to color data into a Color Ramp and plugged that into the Alpha channel. There is also a SeparateHSV node that might work well between the Color output and the Color Ramp. For Eevee, you need to go into Settings and set the Blend Mode. In the picture it is set to Alpha Blend.

Another way of doing it is to mix an emission shader and a transparent shader, assuming this is meant as a light. For this screen shot I added another white cube behind the blue object and turned on Eevee's 'bloom'

Answer 2

Does this do what you want?

• The image color is desaturated with a Hue/Saturation/Value node with Saturation set to 0. (You could also try an RGB to BW node.) The grayscale output is fed into the Alpha socket.
• The ColorRamp is optional, you don't need it. You can use it to adjust how rapidly the gradient falls off by adding stops.
• As always when doing transparency, make sure the material's blend mode is set to "Alpha Blend" or "Alpha Hashed".