Photoshop Brush Tutorial: Shape Dynamics - Roundness Controls

See Also: Shape Dynamics - Size Controls  |  Shape Dynamics - Angle Controls

Up to this point in our look at Photoshop's brush shape dynamics, we've seen how we can change the size of our Photoshop brush dynamically as we paint, and we've seen how we can change the angle of our brush. In this section, we're going to look at the third way that Photoshop gives us to alter the shape of our brush while we paint, the Roundness controls.

First of all, what does "roundness" refer to? Well, if you recall from our discussions about the dynamic size and angle controls, I've been using one of Photoshop's standard round brushes (the 19 pixel hard edge brush, to be exact) for most of the examples. Photoshop's brushes come in two basic flavors - there's the standard brushes which are round and generally not very interesting as far as brushes go, and then there's the "sampled" brushes, which are actual shapes (as in shapes other than circles). Since we're talking about roundness here, I'll use the same standard round brush I've been using, since that will make things easier.

I'm going to make sure I still have my standard round Photoshop brush selected by going to the Brush Tip Shape control panel in Photoshop's Brushes palette (I get to the control panel by clicking on the words "Brush Tip Shape" in the upper left corner of the Brushes palette) and selecting it from the preview of the brush tip shapes on the right hand side of the control panel:

With my brush selected, if you look below the brush tip shape preview in the Brushes palette, you'll see several controls and options, including an option for entering an angle for the brush tip, and directly below that, an option for entering in a Roundness value:

Notice how the Roundness value is currently set to 100%. That's because the brush I'm using is perfectly round. It's a circle, essentially:

In case you're thinking "that brush tip in his screenshot above sure looks larger than 19 pixels to me", I purposely made my brush larger than 19 pixels for the screenshot just so you could better see that it is in fact perfectly round.

Let's see what happens if I change the brush's roundness value to something else, say, 50%. I can do that very quickly by simply typing 50% into the Roundness value input box:

If you look to the right of the Roundness value input box, you'll see a live preview of the brush tip's currently selected angle and roundness. Now that I've changed the roundness of the brush from 100% to 50%, the brush preview no longer looks like a circle. It has a more "squished" look to it. Here's what my actual brush now looks like:

That's how the "Roundness" value affects out brush. Nothing terribly complicated, and up to this point, not terribly interesting, either. But what if we could change the roundness of our brush dynamically as we're painting? Would that make things more interesting? Let's find out!

Randomly Changing the Photoshop Brush Roundness with 'Roundness Jitter'

If you've been following along in order, we've seen that we can allow Photoshop to make random changes to the brush tip shape using "jitter" controls. With "Size Jitter", Photoshop randomly changed the size of the brush as we painted, and with "Angle Jitter", it randomly changed the brush tip angle. "Roundness Jitter" does the exact same thing, except that it changes the roundness of our brush randomly as we paint.

First, I'm going to set my roundness value back to the full 100%. Next, I'm going to set the spacing for my brush tip to 200%, using the "Spacing" slider bar at the bottom of the Brush Tip Shape control panel in the Brushes palette (directly above the brush preview at the very bottom). I'm doing this simply to allow us to see what's going on more clearly than we could if the brush tips were overlapping throughout the brush stroke, as they normally are to give us the illusion of continuously flowing paint:

Now I'm going to go back to my Shape Dynamics control panel, and I'm going to slide the slider bar directly below the words "Roundness Jitter" to the right to set the roundness jitter value to 50%:

Now I'll paint a straight line with my brush and let's see what happens:

When I set the roundness jitter value to 50%, I gave Photoshop a wide range of values that it could randomly choose from to dynamically change the roundness of my brush as I continued painting through to the end of my brush stroke.

If I set the roundness jitter to 100%, I'm telling Photoshop that it can pick virtually any roundness value for my brush as I paint the stroke, from perfectly round to essentially flat:

If I set the roundness jitter value to something much less, say 25%, Photoshop still picks random roundness values as I paint but the values remain much closer to the brush's actual roundness value:

Controlling the Brush Tip Roundness Ourselves

Just as with the Size control and the Angle control, we don't have to rely on Photoshop making random decisions for us. We can gain precise control over how the roundness of our brush changes as we paint using any of the ways listed in the drop-down box to the right of the word "Control:", directly beneath the Roundness Jitter slider bar:

Once again, as we saw with the Size and Angle controls, most of the control options here ("Pen Pressure", "Pen Tilt", "Stylus Wheel" and "Rotation") require you to have a pen tablet installed on your computer. Let's take a quick look at the most commonly used ways of dynamically controlling the brush roundness.

Off

"Off" really needs no explanation. Selecting "Off" disables our dynamic control over the brush tip roundness. Unless you have some sort of value specified for roundness jitter, you won't see any changes to the roundness of your brush while you're painting with "Off" selected.

Fade

Of all the control choices in the list, "Fade" is the only one we can select (besides "Off", of course) which doesn't require you to have a pen tablet installed. "Fade" works exactly the same way here as it does for controlling the size and angle of our brush, except of course that the effect is different. Rather than reducing the size of the brush or rotating it, Fade will gradually reduce the roundness value of the Photoshop brush from its current roundness value all the way down to, well, flat, and it will do this using the number of steps you've specified in the input box directly to the right of the drop-down box where you selected "Fade" from the list.

I'm going to set 20 steps for my roundness fade by typing "20" directly into the value input box:

And now I'll paint a stroke with my brush:

As you can see, the first brush tip in the stroke was fully round, and as the brush stroke progressed along to the right, the roundness of the tips decreased until finally becoming completely flat at step 20. If I had used a larger number of steps, the roundness fading would have been even more gradual and would have taken longer to fade to flat, and if I had used a smaller number of fade steps, the brush would have lost its roundness more quickly.

Pen Pressure

The other very common way of dynamically controlling the roundness of the brush is by using pen pressure, which of course requires the use of a pressure-sensitive pen tablet. You can still select the Pen Pressure option from the Roundness Control list even if you don't have a pen tablet installed, but you'll see a small warning icon to the left of the word "Control" telling you that you need to install a pen tablet for this option to work, and you won't see anything actually happening to brush stroke when you go to paint with it.

If you do have a pressure-sensitive pen tablet, you can control the roundness of the Photoshop brush based on how much pressure you apply to the tablet as you paint. Lesser amounts of pressure will result in less rounded brush tips, and more pressure will increase the roundness of the brush, as shown below:

Applying less pressure to the tablet at the beginning and end of the stroke and more pressure to the middle resulted in my brush being flat at both ends of the stroke yet completely round in the middle of the stroke.

And that finishes up our look at the Photoshop brush 'Shape Dynamics'. In the next section, we'll look at the "Scattering" controls.