Advanced Satori Tutorial # 3 : The Replace brush style

Written and Illustrated by Michael Hirsh. Page 1 of 2

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A Remarkably Useful Tool

Satori offers painters an extraordinary and quite unique tool for re-colouring and re-texturing individual brushtrokes and geometric objects - even text objects.

The tool in question is a Brush style called "Replace", and you can find it in the Brush Setup... dialog boxes under the Styles tab.

At first sight, its name doesn't reveal much about its power and capabilities. However, once you start to work with this remarkable Brush style, your whole method of working with Satori will change, especially for projects that might use Layer masks to constrain paint effects.

What's so special ??

To put it simply, the Replace brush style allows you to re-paint the colour (and to some extent the texture) of part of an object, without adding extra Alpha Channel information.

A Short Demo:

Set up a canvas of 400 x 300 with a transparent background. Use a Solid brush of around 15 pixels and draw a wiggly line across the canvas.

The wiggly line.

Take a look at the Layer List Palette and observe the Alpha Cannel:

At first, Colour Information = Alpha Information.

Now, enter the Styles tab of the Brush Setup... dialogs and check "Replace" and hit the Apply Now button.

Choose a different colour and width, and apply several diagonal strokes across your original stroke.

A few crossing strokes of new colour.

Here are the paths of the new strokes...

And a few more short and curly strokes for fun.

Now look again at the Layer Alpha Channel:

Curious, isn't it ?

You've added all that extra colour information, and yet the Alpha has not changed from the original wiggly line.

Sit back for a moment and think about what this means.
For a start it means you don't need to use a lot of masks to paint within an object. If you can paint inside an object's boundaries with any paint effect you like, and no overspill outside the object, then why use a layer mask ? Unless you might want to invert it, of course.

It also means that you can import an irregularly shaped .RIR file and re-colour all or part of it. This can be a very useful technique for creating texture maps for 3D.

A Few Variants :

The Replace style can be used with any standard brush that normally adds Alpha, (this excludes the Eraser, Shadow and Highlight brushes) and can also be used in conjunction with other Brush styles. Try using the Chalk or Water spinners for example.

The next picture shows the Brush Setup / Styles tab with checks in the Chalk, Remove Alpha and Replace boxes.

This combo sets up a chalky eraser.

The chalky eraser applied to the left hand end of the wiggly thing.

Here's the view from Alphaville.

There's more of this tutorial on the

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