View Full Version : Picking a color as an alpha

06-06-2004, 12:17 PM
Can you pick a color from an imported image map to use as and alpha channel, or is there a way (as in Macromedia Director or Infini-d) to import an image and darken, lighten, additive or subtractive the background color which will not show when rendered. I know how to build an alpha layer in image editor, but that seems to be to time consuming.

Example: blurred type in photoshop imported into lightwave. Because of the blurred areas blending into the black background it would a bit of time to build an alpha channel. Would rather us a darken or lighten command to alpha the black background not to show during RT rendering.

thanks in advance for the help.


06-10-2004, 05:09 PM
Strangely enough I have the same problem right now. The local studio I do work for shot some footage on a green screen. Green screen was not terribly accurate, as a result the green varies quite a bit. I am having trouble dropping the color out using the foreground key option.

I was hoping it might work better in the transparency channel.

Anyone know how I could make only the green areas of a texture transparent. Right now I have the image sequence mapped to a polygon, I need to get rid of the green without manually going into Photoshop and doing a magic wand selection on each image.


06-10-2004, 07:41 PM

first off its not really what LW was designed for, so remember it might make more sense to do these things in a different package.

You can do this sort of thing though. One way to do it is to apply a "Textured Filter" to a clone of the image in the Image Editor and then use gradients to create a suitable Alpha Image/Sequence. For a greenscreen you'll probably need to apply a gradient to the Green, then limit its effect with gradients based on Red and Blue.


06-10-2004, 08:11 PM
Thanks. Luckily, or unfortunately the idea was scrapped. This was a test, but the client of the studio didnt like the idea after it was properly pitched.

I was just getting a leg up and trying to get a head start. I need to get a dedicated matte program of some sort. This is not the first time I have run into this problem.