Advanced Masks in Interactive Groom [5/5] (Patreon)

Earlier in this series we made a nice basic groom in Interactive Groom (IG) using a small subset of its features: sculpt, noise and clump layers and only using a few parameters.

Our focus was on the "interactive" approach to grooming, mostly using brushes and sculpting to create our look.

Let's say we wanted to start adding a lot more complex detail, such as creating different size clumps in different areas. Using the clump brush you'd set up different sculpt layers for each section and create the look by hand.

This can get confusing as you try to keep track of more and more layers and what exactly you did in them. There's another way: using painted maps. You can control many IG parameters using greyscale values painted onto the skin mesh. A value of zero, black, sets a parameter's strength to zero, and a value of white sets it to 1, full. This is a more "abstract" way of working, but it's very powerful and flexible.

Let's go back to our groom project to see how we can apply painted maps to refine the look.

Painting in Maya

First, a few notes about how to use Maya's built-in painting tool. It can be used independently for painting simple textures, but let's look at it in the context of Interactive Groom, which has a specialized workflow.

Every paintable parameter in IG has a paint icon next to it, in addition to a place to plug in an existing texture.

The first time you click the icon Maya will ask you to set up a new texture and then put you into paint mode. It's useful to set a unique name for each map so as to keep things clearly organized.

I use a format like map_density01. Select the folder you want to save in and the image format, then click Create.

In paint mode, the features we'll be using the most are Solid brush profile, Color, Flood, Paint and Blur. These are all found in the Tool Settings panel.

The solid brush is useful since the default soft brush often creates visually unclear feedback, where a section may look black but is in fact dark grey and thus leads to an unexpected result. The solid brush makes sure you're painting the value you want. If you need a falloff between areas of black and white then use the blur brush to soften the transition rather than using the unreliable soft brush. Flood is useful for quickly setting an entire area to one value.

After painting, you can click the Save Textures button (also under Tool Settings) to write the changes to disk. Saving the entire Maya scene has the same effect. There is also a Save texture on stroke option if you want every single stroke to be saved automatically.

One last thing to note is that simply clicking elsewhere on the interface while in paint mode won't actually take you out of it. To work around this you can just select another tool (an easy one is the Select Tool, hotkey Q) to get you back into the normal Maya interface. You can go back to painting on the map you were working on, or start a new one on another parameter, by clicking the appropriate paint icon.

Now let's look at how we can paint maps for our groom!

Painting Maps to Control Groom Parameters

Say we want to have different clumping in different areas. We can control this by painting a map on the Clump Modifer Mask parameter.

Let's set up three different clump layers, following this reference. One for light clumps on the sides, one for medium clumps on top and one for larger clumps.

Paint a mask on each clump layer to control which part of the groom it affects. Remember, black is no effect and white is 100%.

Let's update the lengths a bit by by painting a map on a new scale layer. Increase the overall scale, then mask out parts that we want to be shorter. Grey is used to indicate a percentage of the full scale value: 0.5 grey would be half length, 0.25 one quarter, etc.

We can use this same approach with noise/frizz. In the above reference there is more frizz around the part, so lets add a new noise layer and mask it out in that area.

In addition to painting, we can use one of Maya's procedural noises to control parameters. Let's try this on another new scale layer: instead of painting a map, assign a 2D noise texture.

This breaks up the length in a totally "hands off" way. We can control the look using different noise settings and seeds. Maya gives a preview thumbnail showing what the mask looks like.

With all these layers combined we're getting a more and more refined groom.

Next, I put in an hour or two of work using all the techniques we've covered: adjusting maps, painting density, adding various layers, and sculpting.

During this process, refer to your references a lot and if something doesn't look right stop and ask "why?" Try and explain it to yourself like you would if another person asked for feedback. Often you'll find that the needed fix is simple and limited in scope. Talking it over in your head helps to stay on track and avoid frustration and unnecessary work.

Here's the full description I ended up with:

Now let's add an Arnold shader with dark roots using what we learned in the last article. Looking good!

Closing Words

Since a majority of IG parameters can be controlled with maps, you could in theory sculpt your initial guides to get the overall shape and then do everything else with maps. This is a more old-school way of working and is probably a bit extreme. A good balance would be to use different techniques where they feel most useful. In this case controlling clumps with maps seems like a great solution, but getting into really fine detail with flyaway hairs seems better suited to hand sculpting. It's all a matter of preference.

I encourage you to dive in and play around. If you see a paint icon next to a parameter, paint a map there and see how it goes. You can always delete the layer and none of your other work will be affected. Experiment and have fun!