Now that you have a basic understanding for the 'Canvas' of using Vertex Paint,
I will look at the Vertex Paint Modifier & demonstrate how to animate opacity layers
with it.

The below picture shows the VertexPaint Modifier applied 4 times in the stack, with
two layers turned off. The VertexPaint modifier is designed to be applied many times in the stack,
creating the same type of work flow that you get when working in Layers in PhotoShop.
It also shows that the top ( selected ) layer is working on Map Channel 3.
When starting with VertexPaint, in the Channel options- you can keep it simple by keeping all
of the VertexPaint layers, Vertex Color. This will allow you to see, and use, all of the
different blending modes in each of the VertexPaint layers.

When you do render your textures, sometimes you may get this result:

You may get this result- even if you can SEE that you have a UVW Modifier on the mesh.
This is due to mixed-up Channel selections. Make sure you have all of your Channel settings
working on the same Channel.

When you click the Edit button ( or apply the VertexPaint modifier),
The 'palette' for the VertexPaint Brush opens ( below picture )- with Brush Options that work
the same as they do for the Skin Modifier's- Paint Weights brush.

When you click the Paint Brush icon/ button,

you make the VertexPaint Brush active in your Max scene,
it's the small, light blue cursor- ( same as from the Skin Modifier ).

The brush has a single line that comes from the center of the brush's 'X.'
That indicates the 'normal' direction of the faces the brush is painting on.
The brush can used with pressure sensitive drawing pads- but, the line quality will depend on the
density of the mesh. The more geometry the brush has to work on, the better the line quality.

As I paint with the brush, I get a blurred edge. To get a sharp edge with Vertex Paint, try using the
selection tools;

These selection options are very similar to the Edit Poly selection options.
In the above picture, the Faces Sub-Object mode has been enabled.

In Wire frame view, I then make a selection-
The selected area shows as brown (with a white highlight ), with the unselected faces in yellow.

Now when I paint, only the selected faces will be painted- and the edge will be sharp.
Many times when I select an area of faces like this, I will use the Paint Bucket option-
this will fill the selected area with the color that is active in the Eyedropper / Color Palette,
and is much faster than painting faces.

I'll now experiment with painting on the mesh; with selections, or just dragging the brush, etc.
to create some painted effects/results- as in the below picture;

I'll then click on the very bottom 'Add Layer' button in the Vertex Paint brush Palette;

A window will open, asking what Channel I would like the new layer to be-
(image below)

Map Channel has been selected in this picture, but for now use Vertex Color.
When you use Map Channel, you get a 'clean' slate to begin working on- which is great,
but for this demo -I want to effect the other layers of the VertexPaint modifier
with the Opacity setting, and the Blending modes- which is very straight forward in the Vertex Color Channel.

On this new layer, I will paint some additional area's, and switch the top layer Mode to Multiply;

My new layer will now be seen with my first VertexPaint layer, again
very similar to how PhotoShop works with Layers and Blending modes
( Thank You Discreet! Very Cool! );

And finally, the ANIMATION part :)

Now, by turning on Auto-key, you can animate the slider in the
Opacity setting:

This gives you the ability to animate the VertexPaint layers fading in and out on your mesh.

That's it! Nice and simple, with LOTS to experiment with.

I strongly recommend taking a look at the 3DS Max Reference files on the
VertexPaint modifier, a great deal of additional information is given.
Discreet covers ALL of the different options in the VertexPaint Toolbox.
And, Discreet explains how to Animate Vertex Color- using the
UVW XForm Modifier ( very cool :)

Thanks!

Josh Purple