The Maya Journal: Modeling the Mech's Arms

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In the last edition of the Maya Journal, we modeled the overall structure of the mech's upper torso. To accomplish this, we learned about the differences in world and local space, how to extrude materials, and how to bridge between two edges. These tools and knowledge let us build a set of thrusters, hoses and shoulder guards. We'll continue with modeling the mech's arm, which contains a retractable machine gun, and a set of mechanical claws.

Modeling the Arms

Building a robotic anatomy is obviously much easier that a human one, but for beginners it can still be pretty challenging. Even though our character is a mech, we will still model it like a human body. That is, the arms and legs will have joints on which the upper and lower appendages will rotate. In fact, we will begin by modeling a shoulder joint to be placed directly underneath our shoulder guard. This shoulder joint will take the form of a sphere. Create a polygon primitive sphere and bring it roughly into position under the shoulder guard. Check the orthogonal views to make sure it's seated properly. Make sure to align the sphere's poles (north & south) along the length of the arm. What you're doing is changing their local coordinates. We need to keep our polygon count down, so change the sphere's subdivisions (i.e. axis & height) to 12. You can do this in the channel box. It's important to keep polygon counts low, and any hidden objects like this shoulder sphere are great low res candidates.

Deformers

You probably will run into the problem of your sphere being a bit too big to fit comfortably underneath the shoulder guards. Mine penetrated through the back, near the thrusters. Don't worry because there's an easy way to fix this by creating what are called deformers. Essentially, deformers are three-dimension grids you can create around an entire object. You might think of them sort of like hulls around a NURBS surface, or just a larger control surface. Deformers are kind of like cages surrounding an object with handles that let you "deform" it. To create a deformer, first select the entire torso. Then change your menu set to animation. On the main menu, choose the type "lattice" under create deformers, but first go to the lattice options. You will want to adjust the settings to the values below. Finally hit create. Now you should have a lattice work that surrounds the mech torso: Manipulating the lattice is just like any other object. RMB on the lattice and choose lattice point. Then select the set of points closest to where your sphere is penetrating the back of the mech and move them backward. Make sure and select ALL of the points that run through to the other side of the lattice or you will only be deforming part of the torso. After you've gotten your torso adjusted, you can delete the lattice in the outliner. Since you've moved the back away from the shoulder guard, you will probably need to deform it, moving it back as well. Just apply the same procedure.

Upper Arm

We can build the upper arm by simply extending it from the sphere. There's no need to add more geometry. We can use what we already have. First select several rows of faces at the end of the sphere. Then choose extrude, but before you move the faces, go into your move tool settings (i.e. click and hold on the move icon) and set the axis to object. This will ensure that your extrusion moves straight down the arm's axis and doesn't spread out at the ends. Finally extrude the faces only a short way down as in the image below. Delete the faces when you're done. Building the upper arm now involves creating a polygon cylinder, scaling it, and placing it in position with the last extrusion. Make sure and check your orthogonal views to make sure it's placed properly and is the correct length. As you can clearly see above, the cylinder is much smaller and uniformly shaped when compared to the image plane. However, you can model it to fit this shape quite easily. First we'll need more polygons to work with along the cylinder's height. In the channel box, bring the number of subdivisions down along the axis to 12, but increase the subdivisions along the height to 4. Then create two new subdivisions in the cylinder's cap. With the new subdivisions, you can select the edges and scale them out to form the shape of the upper arm. You can select the vertices on the cap (near the shoulder) and scale them out as well. Select the interior circle on the cap to finish the upper arm. Scale it to create a thickness to the upper arm. Next, extrude those faces inward to make to make a hollow section where the elbow joint will sit. Finally delete the faces. You may want to insert some edge loops to tighten up the edges of the upper arm. When you've finished, you should have something resembling this: