what is matte?

[jussing]

It's all about transparency in images.

Simply put, a matte is a black/white image - or MASK - used for compositing, for instance in bluescreening.

When filming actors in front of a bluescreen, a compositing program is used to "pull a matte" like this one:

http://static.highend3d.com/tutorialimages/17/fig_5_6_7.jpg

-which basically represents the image's transparency, allowing the user to insert a background image behind it. (the concept of mattes dates from far before digital compositing, in the old days they made them using blue filters and black/white film)


An ALPHA CHANNEL is a fourth channel in a digital image (besides red, green and blue), which stores the transparency information for the image (which you might call a matte).

Cheers,
- Jonas

[Darth Mole]

The key thing to remember is that masks or alpha channels are greyscale images - shades from black to white. They themsleves do not contain any transparency - what they do is control the level of transparency on other layers. Like how a greyscale image can be used to displace an image or to attenuate an effect.

Once I'd got my head round that, it made things a lot easier!

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