How do I paint inside an existing object?

[bobdobbs]

In Designer, I have created a pixel object.
Now I want to use a raster brush to apply shading to the object.

I've switched to the pixel persona, selected a brush and selected the object.

How do I prevent the brush activity from affecting an area oustide of the target object?

[R C-R]

How many other objects (layers) are there in the document? If there is just the one, you can probably use the Flood Select Tool to select everything outside that object, use Select > Invert Pixel Selection to get a 'marching ants' selection that you can paint into using a pixel brush.

If this isn't working or what you want, please provide more info & possibly an example file.

[thomaso]

The brush option "Protect Alpha" (the last in the Context Toolbar) might do what you want.