Let’s Get this Robot Moving: This tutorial assumes you have already modeled your robot, “Papero”. I have done a few preliminary tasks to make this tutorial easier to follow:

For animating we will take the Papero model we made in the modeling a robot tutorial.

With simple characters, such as our robot, you don’t need a lot of complicated movements. In fact you could probably get away with just using simple keyframing of his head moving from side to side, and adding additional keyframes as he changes location. But then this would be a very short tutorial, and rather unnecessary as you could figure that out all by yourself.

The fact that Gaurav modeled “Papero’s head as all separate parts, presents us with an interesting option for giving our robot an interesting action set. We are going to animate the ear rings and ear ball shooting out from the side of his head as he rolls along. We are going to accomplish this by using Action Constraints.

The basic premise of Action Constraints is simple. You create a set of actions once, then attach that set of actions to one bone with an Action Constraint. When you rotate the one bone, the set of actions gets triggered. Pretty slick time saver, it also assures that the action will be consistent throughout your animation.

This tutorial was created with Blender 2.40 alpha-2. (If you have a previous and or possibly newer version, this should not be a big problem as Action Constraints have been around for quite a awhile.)

So let’s get started.

At this point you can go back to your Ear action and add in actions for the right side of the robot, so that both sides pop out at the same time. After you have added in the new actions for the right side, don’t forget to add action constraints to the right side Ring 2.R and Earball.R bones.

At this point ‘Papero’ is ready to roll. He can be keyframed to move across the screen, bump into things and show surprise (his ears popping out).

To practice on you own, here are some further suggestions on actions you can add to our little robot ‘Papero’ to give him a little more character:

• Make his head pop up a little off of his body
• Make his body pop up a little off of the wheel base
• Have Ring 1 and Ring 2 rotate slowly back and forth while he is rolling through scene.
• Have the Earball slide ever so slightly in and out of rings
• Move Head back and forth sideways as if he is scanning his surroundings.

Have fun with your new little robot.

References & External Links

• .blend file

• Modeling A Robot

• Texturing A Robot

Written by Sandra Gilbert (aka dreamsgate)

This article deals with the modeling and animation of gears, providing a short tutorial for the utilization of the Blender Mechanical Gears (BMG) script.

Introduction. One of the key points in modeling and animate mechanical devices relies in the need to produce gears. Gears are not merely “wheels with teeth”. Gears were like that in ancient days, but modern mechanics deeply studied the different ways in which spin can be transferred from one rotating axis to another, defining exactly how a gear must be designed for maximum efficiency.

Some theory can be obtained from the docs on [1] (I don’t want to promote any particular gear manufacturer, but this is the reference I used to create my gears) as well as in the Blender Mechanical Gears (BMG) script documentation [2]. Basically a gear must be designed so that no friction occurs at two meshing gear teeth. This ensures efficiency, long duration, and low noise. The mathematical description of a gear is based on the involute concept. The involute of a circle has several properties; the most important of which is that teeth of meshing gears whose profile is an involute do not slide one on the other while the gears rotate, and the pressure angle with which a gear pushes the other stay constant.

I will not go deeper on this here; you don’t need to know, since the BMG will handle mathematics, but if you are curious just browse [1,2].

Main Gear Parameters. This group of parameters defines the basic look of the gear. When two meshing gears are set what defines the geometry is the Pitch Radius, which is the radius of the ideal circle on which the meshing teeth of the two gears touch. It is the pitch radius the one defining most of the gear geometry. This, as most over entries, is defined in Blender Units. We will keep the default 5 for now. The teeth number defines how many teeth the gear has. This is the second most important parameter, and we will set this to 25 for this example. The Pressure angle is vital, from a mechanical point of view, but is of less importance in computer graphics. It defines the angle between the tangent plane to the gear tooth at the contact point and the plane containing the two gears rotation axis. It is probably better to leave this to the default 20° value. Helical Angle defines helical gears shape. Common gears have straight teeth. Helical gears have slanted teeth. Helical gear are less noisy and more swift in operation, and more costly to manufacture, all things you don’t care in 3D graphics, so we will keep this angle to 0 now. The Addendum and Dedendum defines how far beyond and beneath the pitch radius the teeth extends. These parameters are critical. First the Addendum cannot be greater than the dedendum, or you will have big meshing problems. Second, Their value must be tuned according to the number of teeth. The more the teeth, the smaller these two must be, the fewer the teeth, the larger they can be. For our example 25 is an average teeth number, so we can keep them to the default 0.4 value.

Beveling: No true mechanical devices have sharp edges. Fillet defines the radius of the rounding at the top and bottom of the tooth. Bevel defines the beveling of all edges on upper and lower face of the gear.

Mesh Parameters: The script generates a single tooth for the gear, with a given refinement level in the mesh. The refinement level is given as a Resolution along the tooth perimeter, which should be kept to 2 unless you are planning to zoom in a lot (rise it) or zoom out a lot (lower it) on your gears and a Longitudinal Resolution along the tooth thickness. This is actually needed only for helical gears, which do exhibit longitudinal twist. Finally the Thickness defines how thick is the gear and the Width defines how much to the inside, with respect to the pitch circle, the body of the gear extends beyond the tooth. Keep all these to their defaults

This is necessary because the spinning script (BMGs) will handle rotations for the gear as relative to the z axis. If the gears are to be moved and are not lying on the xy plane this will results in odd behavior.

By parenting gears to empties and by moving/rotating only the empties from now on – never the gears – the animation will behave properly.

Now launch the BMGs script. It is an ‘Animation’ class script. It will present quite an empty interface, with just an Add button. Press it four times and four lines will appear. In these line first column presents a Gear Object name. Fill ‘Gear’ in the first and ‘Pinion’ in the second, ‘GearB’ in the third, ‘PinionB’ in the fourth. Second column specifies the teeth number. ‘Gear’ and ‘GearB’ have 25, ‘Pinion’ and ‘PinionB’ have 12. This completes our gears database (Fig. 9.1). The gears database holds info on which objects in your scene is really a gear and should be spinned. You can Save and Load database to/from disk, the script generates XML files. You are advised to do so because the databases will be lost when you quit blender (The automatically generated script for spinning will not be lost!)

Now switch to the ‘Link’ Panel. Add three lines here with the Add button. The new lines appearing contain information on which gear is connected to which other. The first column in each line contains the driving gear, the second column the driven gear. The third column specify the link type, which can be a mesh kind of link, in which the pinion rotates in the opposite direction with respect to gear and the speed is given by the gear speed modified by the tooth number ratio. For coaxial gears, that is, for gears not meshing but rather mounted on the same axis the link type is fixed because the rotation speed is the same. In rare cases, with crowns and helical gears, the speed might still be in the tooth number ratio but not in the opposite direction. For these cases the InvMesh option exists.

In our example in the first line we will state that ‘Gear’ is the driver, ‘Pinion’ is the driven and the link is of ‘mesh’ type. On the second line ‘Pinion’ is now the driver, ‘GearB’ is the driven and the link type is ‘fixed’ since they are rigidly bound. At last, third line states that ‘GearB’ is the driver to ‘PinionB’ in a ‘mesh’ type link.

References & External Links

• http://www.bostongear.com/pdf/gear_theory.pdf

• http://projects.blender.org/viewcvs/viewcvs.cgi/bstar/BMG/BMG-0.0.2.pdf?cvsroot=bstar

• http://projects.blender.org/viewcvs/viewcvs.cgi/bstar/BMG/?cvsroot=bstar

Written by Stefano-Selleri