FOR: LightWave 3D 9.5
TIME TAKEN : Three hours
TOPICS COVERED : Setting bones to move geometry | Setting up bones to mirror movements | Arm animation | Full body animation
DOWNLOAD: Full-sized screenshots and scene files (ZIP, 32.7MB)
How to use this tutorial
Pause at a timecode, read the overview of the next section of the video, then play the footage. Please note that these screen-capture videos do not have narration.
Rigging the upper arm
The biggest issue you’ll encounter when making a transforming robot is the sheer complexity of it. This section of the tutorial will break down the rigging process into more bite-sized chunks. In this case, you will be rigging the upper arms only, so that we can go into detail on the methods involved in rigging the parts. During the rigging, you will also be implementing a tool called ‘Follower’ to help speed up animation.
There is a main concept that is important to any transforming robot: a base skeleton. Remember, it’s just a humanoid form trying to get out of its shell. Even with all the nurnies and parts that will be shifting around, it is always good to have a standard skeleton folded up in the mix. The position of each skeleton piece should be evenly distributed so that each section gets just about the same volume of metal from your vehicle. This is important to plan out, since you don’t want too many or too few extra parts at the end of your transformation.
For a humanoid, there are about 15 skeleton pieces that require your vehicle parts to cover them. These include the feet, lower legs, upper legs, pelvis, spine sections, chest, upper arms, lower arms and hands. The head is usually not made up of any of the vehicle’s geometry, but should be textured similarly, to give the illusion that it came from the same material. After you set up the base skeleton, you can parent the pieces to be children of their closest skeleton bone. The upper arms on the train, for instance, use a cylindrical section of parts near the centre of the train. As explained before, this video focuses on the process of rigging the upper arms (both left and right).
After loading the start scene with the train inside, it’s time to isolate geometry. I have created an object that only contains the pieces that will be included in the transformation of the upper arms. It’s best to simplify things this way, as it can become overwhelming once you add a bone for every part of the train. A second advantage of an object with isolated geometry is the fact that it will be considerably faster than all of the polygons at once. In LightWave 3D, you can replace an object via Item > Replace > With Object.
Add your base bone
Add a bone by clicking on Setup tab > Bone. This bone will be the base upper arm bone. I name it in all-capitals just to remind me that it’s an important base bone, which will be the parent of all the moving parts. It’s very important to add an ‘rt’ or ‘lt’ at the end of every piece to signify whether it is on the right or left side.
The next step is to place the bone close to all of its parts, so the parts don’t have very long to travel to get to their destination position. Press the [P] key to access the bone’s properties and set Strength to 0. Base bones do not require any strength, as they will be the parent of every piece. After placing the base bone, I changed its colour to red in the Scene Editor [Ctrl]+[F1]. It’s optional, but a noticeable colour helps signify the bone’s importance.
Start to add bones to each individual piece of the robot. Take care to keep naming conventions consistent
Add kibble bones
Oddly, this section has nothing to do with dogs. Kibble is a Transformers fandom design term: it refers to any part that doesn’t seem to have a purpose on the robot in its humanoid form, but exists because it was a part of the original vehicle. One of the best examples of this is the car doors that appear on Bumblebee’s back in the Transformers movies. I take a slightly inaccurate approach and refer to every moving part as kibble, not just the odd parts.
Start by adding a Child Bone of UPPER_ARM_RT: name it uparmkib01_rt. Naming pieces on a transforming robot can get a little confusing, since you can’t make up a name that perfectly describes the piece that the bone moves. Sometimes you can find a particular order in which to name them; sometimes you’ll just have to pick a random part to be ‘upper arm piece #15.’ After naming your first kibble bone, set its Strength to 100% and select its Bone Weight Map from the (rather long) list. These Weight Maps were pre-made in Modeler.
After giving the bone the correct Bone Weight Map, it is time to see exactly which piece of geometry it influences. Press the [R] key to rest the bone. Now, as you move the bone, you will see the geometry move as well. If your bone is not close to the piece, unrest it with [Ctrl]+[R] move it to the centre of the piece and re-rest it with [R] again. It’s also a good idea to keep the length of the bone (Rest Length) similar to the size of the kibble geometry. Now you have successfully rigged the first piece. There are plenty to go… The cloning technique shown in the video will help to speed up the process.
Finish the right side of the rig by adding bones to the wheel section. Use a master bone to control the section
Move pieces inside
The process for adding bones to control the pieces is similar to what you did for the first kibble bone – so it’s basically time to be tedious and repeat the previous step a few more times. The wheel and coupling rod should also be rigged during this process, as they are also considered kibble.
At this point, you probably have noticed that there are weird floating pieces on the side of the wheels. These pieces are meant to go inside the shell of the train, between the wheels. Why are they on the outside? It is much simpler to model and rig them this way. Can you imagine trying to select parts if they were all bunched up together in a big clump? Not fun. So let’s rig that bunch so it can be put inside.
It’s a good idea to create a master bone for this bunch, so it can be moved as a whole. Start by making a bone in the middle of the wheel-like part. This serves as the top of the hierarchy, so all other bones added for the bunch should be a child of this bone. Repeat until each part has been rigged. After you finish rigging the last piece of the right side, it’s time to handle the left…
Mirror a hierarchy of bones and edit its labels so that the left-hand side matches the right
Mirror the hierarchy
Rigging the left-hand side is be much less painful than the work you did on the right. You can simply mirror the bones you’ve created so that you have the same hierarchy on the left. Start by selecting the UPPER_ARM_RT bone. Go to Setup tab > Mirror Hierarchy, or press [Ctrl]+[W].
If you’ve never used this tool before, it mirrors the bone you have selected and all of its children along the X axis. But that’s not all… Using the drop-down menus for Replace this string and With this string, you can replace any occurrence of ‘rt’ in the names with ‘lt’. This will automatically rename the bones on the left side with an appropriate ‘lt’ suffix. Even better than that is the fact that the new bones will use Weight Maps with an ‘lt’ instead of their original ‘rt’.
When I used this tool, an odd glitch occurred after I mirrored the hierarchy, which seemed to offset the base bone by a random position. After clicking on several different bones, the position seemed to correct itself.
Set up Follower to mirror animation
The final step in rigging the upper arms is to set up a Follower modifier on all of the kibble on the left-hand side. When set up correctly, the left-hand kibble will mimic the movement of its right-hand counterpart as you animate the latter. This is extremely useful for the animation process, since it cuts time in half.
Click on the first kibble bone of the left-hand side (uparmkib01a_lt). Enter Motion Options for the item by clicking on Setup tab > Motion Options. (You can also press [M].) Click Add Modifier and select Follower from the list. This tool sets all the Position, Rotation and Scale channels of your item to follow another item. Select uparmkib01a_rt from the Item To Follow drop-down menu.
By default, your bone will follow all channels exactly. But to get correct results, you want to have the movement mirrored along the X axis. This is a simple matter of multiplying X Position by -1 instead of the default 1. Set the Multiply by values of Heading Angle and Bank Angle to -1 as well. This will allow mirrored rotation as well as positioning.
Select Continue and right-click Follower to make a copy of it. Select the next lt bone and paste Follower in its Motion Options. Now the only thing you need to change is Item To Follow. Repeat this workflow until all of the kibble bones on the left side have Follower applied to their motion. It is always a good idea to check your bones while you work to make sure they are moving correctly.