View Full Version : Help creating perfect Alpha

12 December 2005, 07:35 PM
I have noticed that after painting an alpha channel and applying it a 3D model that my alpha isn't a perfect match with the color. I always have a little bit of difference between the two.

When I create my alpha I am pretty much just selecting the areas I want to be opaque and paint bucketing them.

Does anyone have any tips on a proper way to make an alpha channel. Things to avoid and keep in mind, etc.


Ian Jones
12 December 2005, 01:22 AM
where exactly do the differ? just around the edges?

12 December 2005, 02:39 AM
A few pixels outside of each selection. My suspician is that it's caused by antialiasing.

12 December 2005, 01:20 AM
I never have actually tried this method, but my partner says it makes the best alpha maps. The way he does it is he paints the alpha channel first, by creating a new channel in the channels box. Paint it by hand with a 100% hard brush and see how it turns out.

I'm not sure how he ended up colouring it, I only saw him do it for some grass textures but have a go at experimenting anyway :)

I hope it helped!

12 December 2005, 04:55 PM

this is by far the best masking tutorial i've found. Go to advanced masking at the bottom of the page.


>>edit. Sorry this is more for 2D than 3D but very useful all the same

Jack Youngblood
12 December 2005, 05:29 PM
The best way to tidy up an alpha with a shaggy edge is:

1. Blur the alpha slightly. This creates a graded grey fringe between the black and the white areas.

2. Play around with Levels Adjustments (middle slider I think). This will gradually convert the grey fringe into white or black depending on your settings. You will effectively be presented with a 'live' feedback of a shrinking/enlarging of your mask.

You can do this either with the mask in preview (cant remember the keystroke) or on the mask with the image in preview.


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12 December 2005, 05:29 PM
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