Photoshop 3D – What’s an Extrusion?

As I was experimenting with Photoshop CS5’s new Repousse feature for 3D last week, I had the sudden realization that I hadn’t had this much fun since I was a kid. And that led me to the realization that a certain children’s toy was in fact a great real-world example of the basic principle of Adobe’s Repousse – the “extrusion.” As an engineer by trade, I’m very familiar with that terminology, but I realize that this isn’t a term everyone uses, so an example is in order.

Off I went to dig out my granddaughter’s Play-Doh Fun Factory. You’ll recall from the dusty cobwebs of past memories, that you place a glob of Play-Doh into the cavity, and push it through a variety of shaped holes to create fun strings of Play-Doh. These shapes are extrusions!

Now the real power of extrusions and of the “Fun Factory” is the ability to change shapes to produce different results. You get a series of interchangeable shapes like so:

And, if we choose the leaf shape, we can force the material through the shape to create a unique “noodle” of Play-Doh:

The longer we push, the longer the noodle gets, and we can bend and twist it as we extrude:

Now, Photoshop’s Repousse feature works almost exactly like this, except without the cleanup! Plus, we can change some of the features after the fact if we don’t like the results. For example, let’s start with this custom shape I’ve created, and have placed in my image as a shape layer:

Just as with the Play-Doh, we can extrude this custom shape using Repousse. With the Shape Layer highlighted, choose 3D > Repousse > Layer Mask… (if you have the path selected, you can also choose Selected Path, the result is the same):

As we saw last week, Photoshop will warn you that the shape layer will need to be rasterized. If you want to retain the shape layer for future use, you’ll need to make a copy before proceeding:

Once you click “Yes,” you’ll get the Repousse dialog box, and you’ll be able to see the extrusion effect live in real time as you make changes. Set the following parameters:

Extrude:

• Depth = 3
• X Angle = –30
• Y Angle = 30

Bevel:

• Sides = Front and Back
• Height = 5
• Width = 5

At this point, you should see something similar to the results below. I’ve annotated the various parts of the extruded Repousse object to help you identify the various parts of the “anatomy” of the object:

Remember, you can hover your cursor over the object, and drag to rotate and roll the object. You can even twist it all the way around to see the back side. You can (and should) always click the “Home” icon before you exit the Repousse dialog to bring the mesh back to its original position:

When you’re through experimenting, click the “Home” icon and then click “OK” in the Repousse dialog box.

Note that in creating this mesh object, the extrusion came out grey instead of picking up the object’s green color. I’ll show you how to change that next, and that will be a good preparation for next week’s tip in adding materials.

Let’s start by opening the 3D Panel (Window > 3D). In its initial view, the 3D Panel shows the components of the scene at the top, along with a variety of contextual settings at the bottom. These change as you select different objects. Right now, we have the entire scene selected (as shown with the blue highlight):

We want to change the extrusion material to match the front and bevel, so let’s click the third icon at the top to “Filter by Materials” (this limits the list of components to just materials and changes the context items in the rest of the panel). Then, look in the list for “Shape 1 Extrusion Material” and highlight that, like so:

Now, to change the color of the extrusion material, we need to change the “Diffuse” property. Click on the grey color swatch next to the word “Diffuse,” and a color picker will pop up; you can then choose the green color from the front face with the eye dropper:

Once you click the eyedropper, the color is updated immediately. We now have a matching green color for the extrusion material.

There, you’ve modified your first material! That wasn’t so hard, was it? Keep on experimenting, if you’d like, changing the materials for not just the extrusion, but the other mesh objects as well. As you can see, the Repousse tool offers a great way to create real 3D objects within Photoshop, from almost any shape you can imagine. Nearly as much fun as Play-Doh, and without the cleanup!

Next week, I’ll take a look at using some more interesting materials, and creating a more realistic object that includes more organic textures.