Rigging Mechanical Robot

by Didik Wijaya

As I promised before, I will wrote about Gundam tutorial, from modeling, texturing, and rigging. So, this is the LAST tutorial: How to rig a mechanical robot like Gundam RX-78-2. There are many ways to make a poseable robot Some people prefer just to use pivot point and link one body part to another. Others using bones or skeletons to move body parts. This tutorial will show you how to rig a human like robot. As you can see, Gundam RX-78-2 has body parts and joints similar to human. Surely, you can use technique described here to any robot.

1. First, you need Gundam 3D model. You can download here. This 3D model is already textured. After you download, import 3ds file (File>Import). Freeze all objects if you want (Freeze option is available in Display tab). Now, create Bones. Go to Create>Systems. Click Bones button. In Front viewport, click three times to create bones (1-2-3), after that right click to finish creating bones. You will have one small bones at the end of bones hierarchy. You can delete this bone. Select all bones and move to the center of objects. As result, you have bones for body and head.

2. Next, I will use IK (Inverse Kinematics) to move the legs. IK is a system that enable you to move whole bones at once. To understand IK, look at your own leg. You have upper leg, lower leg and foot. If you are not using IK, that means Forward Kinematics, you rotate upper leg, then rotate lower leg, and last rotate the foot. In IK, you just need to move the foot and other part of leg will adjust itself.

Before I create IK, I need to adjust leg position. I rotate and move legs until I get some angle in knee. You need to do this in order to make IK simpler to create.

Create bones, this time activate Assign To Children. Other option Assign To Root will also active. Click four times in Left viewport to create bones like image below. Right click to finish. You'll see (+) object before the last bone. This is called IKChain or Goal . Try to move this goal and you'll understand what IK is all about. Press Ctrl+Z to undo.

3. I need to move Goal to the heel position. Most common, people use IK legs from upper leg to lower leg, and moving or rotating the foot manually. Make sure Goal is selected, and go to Motion tab. In IK Solver rollout, click button under Pick End Joint. And click bone shown in image below (white arrow). Goal will move into new position, but bones position will also move. Move Goal into heel position and all position will be fixed. Delete small end bone if you want.

4. Make sure all bones for leg are in center. You need to make bones for other side of leg. Hold Shift while moving to other side to duplicate bones.

5. Creating IK for arms is almost the same with legs. Before yo do, make sure you rotate or move arms object to assure adequate angle in elbow. Create bones with IK in Front viewport (from upper upper arm to palm). Move Goal in wrist area. Look at image below for reference.

6. Zoom in hands area. Create bones for fingers This time without IK. Before you create bones, make sure to decrease bone width and height. Adjust bones position in Left viewport.

7. Next, link finger bone to the palm bone. Click Select And Link tool. Select bone closest to palm bone. Click this bone and drag to palm bone until cursor is change and release. White flash will confirm that they're linked. You have to do this five times.

8. To create bones for other side of arms use Mirror. Select all arm bones. Use Mirror Tool (Tools>Mirror).

9. For thigh closure (thin object surrounding pelvis), I create one bone for each object. That means I create 4 bones. I don't create bones for side closure. Right image below shows all bones.

10. In Command Panel, go to Create>Helpers. Click Dummy button. Click and drag in Top viewport to create dummy object. Position dummy in pelvis area. Actualy creating dummy is optional. I use dummy for easy selection. When all geometry and bones visible in viewport, it's hard to see and select body/pelvis bone. It's easier for me to select dummy instead.

11. Right now, all bones not yet connected to each other. First, link arm bones to body/pelvis bone. Suddenly, arm bones rotate. To fix this, select IKChain/Goal, go to Motion tab. In IK Solver Properties rollout adjust Swivel Angle to 90.

12. Link the rest of bones to other bones. Image below shows how the connection must be. Everytime you see the bones rotates after linking, adjust Swivel Angle value. Usually value 90 or -90 will do just fine. Finally, link body/pelvis bone to dummy.

13. Usually we need skinning process when using bones. But fortunately we work with mechanical object. They are all stiff, un-deformed object. So, you just need to link each body part to corresponfing bone. For example head object linked to head bone, body object linked to body/pelvis bone, and so on.

Exception:
- link side closure to body
- link two shield object to left lower arm
- link shoulder to body
- link rifle to right palm.

14. When above step is finished, try to move dummy or IKChain/Goal. You'll see all body part following bones movement. Next, one small but important step. Select each IKChain/Goal and rename it (look at image below). This way, you can easily select this IKChain by opening Select by Name window (press H in keyboard).

15. Now, the fun part. Pose your Gundam 3D model. Move IKChain or dummy to get the pose you want. Other objects movement; like head, fingers, palm, rifle, foot, and shield, must be rotated manually. Tips, when you rotate object use Local coordinate system. Images below show my experiment.

Thank you for following this Mecha tutorial from start to finish. Congratulations. And be sure to visit Escalight.com, as this site will be updated with more quality tutorials and free stuffs.

source from: escalight