Trying to use black and white JPG for alpha channel

Hi, this is my first post to BlenderArtists. I have tried looking for a similar post to my question but haven’t found one.
I have a material UV mapped to a Mesh Plane that uses a JPG image as a texture. The texture is set to Influence the Diffuse Colour. When render I see the image on the plane. What I want to do is add a black and white JPG image to effect the alpha of the material.

I know I could use a PNG image that has alpha instead of 2 images but I’d like to do it this way. I’m sure it’s possible but I don’t know how.

Can anyone help?

thanks, mookinx

  1. Don’t use jpg images. It’s a web format, not a 3d graphics format. Jpg images have no alpha channel
  2. Use png textures, which have alpha channels (or at least transparency).

I know you want to ues jpg textures for some reason, but do yourself a favor and don’t.

You need to add both of the images to the material. Then in one texture channel make the image affect color. Then in the other channel (black and white) make that image affect alpha and NOT affect color. Once you have that setup you have to pop over to the material itself and set the alpha to 0.0 and make sure Transparency is turned on and use Z-Transparency, NOT Mask or Raytrace.

Here is a little example all setup.


25_alpha_card_dual_img_mat.blend (406 KB)

do this but also check RGB to Intensity and that will tell blender to use black parts as trasparent and white parts as full alpha

Thanks Atom, your attachment was a great help.

I had used Material> Transparency> Z Transparency before in my ‘random clicking buttons to see what does what’ moments to see if I could get it working but had neglected to set Alpha to zero. In my thinking when Alpha is at 1 that means Alpha is fully enabled and when 0 the Alpha effect is turned off. Also I saw that alpha only shows in the viewport when Display> Shading=GLSL.