The GIMP

Hi! I need to make smoke in Blender, I did it with an image of a cloud and some logic bricks in the engine and it worked!
Now I want to make the smoke darker so I must change the cloud image I used (and didn’t create it). I need an image of a dark cloud but in the image only the cloud must appear, not sky, nothing else but the cloud and the background of the image must be transparent. I know this can be done with the GIMP but isn’t working, how can I make an image of just a cloud and NOTHING else

If I knew I’d tell you … but I hated GIMP from the get go …

md01

use the dropper tool to select the background color, then go to filters>>color>>color to alpha. That’s one way to do it.

Add a transparent layer. Delete the background layer. Paint you smoke. Then you can save it as a png. If you can’t use png and need a alphachannel, rightclick your smoke layer, selection from alpha, then save to alphachannel.

Modron’s got it right for you. You could also start with a transparent image and paint your cloud on it… that way your alpha is already there. Alternately, if you are working from a pre-existing cloud image (maybe you’re color-tweaking it or something) that has a background in it, you can use a combination of fuzzy select, erase, and lasso to remove the background. If the original image is a jpg, you might need to duplicate layers and erase the background layer before you begin erasing. Otherwise, you’ll be erasing to whatever your background color is, rather than transparent.

Also, make sure you’re saving in an image format that supports alpha channels (png or tga being the most prevalent).