Basic Aircraft Animations

When building an aircraft model there are some basic animations which are really "no brainers", but getting them to look right takes some knowledge of how the process works.

Just as our 3d world has it's "point of orgin" (0,0,0) in 3d space and all points are relative to it, each part or group of parts have their own point of origin. We refer to this as the pivot point for that part or group. You can think of it in a relationhip much like the universe. Galaxies revolving around a central point, our solar system revolves around a center point in the Milky Way. The earth and other planets in our solar system revolve around the sun. The moon revolving around the earth. This forms a hierachy. A parent - child relationship. While the child can have its own individual life, it is influenced by its parent which inturn can be influenced by its parent. Your fingers are children of your hand. Your hand is a child of your forearm. And so on up the chain. You can move your fingers without moving your hand but if you move your hand your fingers move with it. If you move your forearm your hand and fingers move with it. This is a hierarcy too.

The most basic of part animation takes place at the extreme bottom end of the hierachy chain. In our 3d world of animation, if a part has no direct parent to exert an influence over it, then it is a child of the world. This part has a point that is refered to as its pivot point. If you recall your basic algebra from school and when you were making graphs, we had an X axis. Next they threw in a Y axis. And in 3d we have a third Z axis. Bottom line was that you plotted points on these graphs based on the scale of the axis.

Now lets say you have made a graph and plotted a line of points on this graph. Think of this line of points as a part. If the piece of paper you have your graph on is laying on your desk it is pretty simple to understand where the line goes or where the part is. In our aricraft modeling the axis are oriented so that looking down from the top the X axis runs from left to right, the Y axis runs front to back and the Z axis is pointing at your face. Now take that piece of paper and stand it up vertically so that it is on its bottom edge. Congratulations, you just rotated around the X axis. Now with the paper still on its bottom edge, turn the paper so that that bottom edge is perpendicular to you. You have now rotated around the Z axis. Lastly, just turn the paper up on one end and you have rotated around the Y axis. Notice that the points are still in the same place in relationship to each the axis and to one another. This is the basis for a rotating animation.

I will be working in gMax v1.2. and we will be dealing with the most basic of the animations here; those for a rudder, elevator, aileron, simple flap, and a propeller or jet turbine fan. It is assumed that you already have an aircraft model built with the necessary control surfaces and other objects that you wish to animate and have completed texturing it.


During the the construction phase it is not uncommon for a parts axis to get oriented to something very strange so before I start my animations I will go to the Hierachy Panel and re-orient the axis and lock it in.

With the part selected, in this case the rudder, click on Affect Pivot Only then Center to Object and Align to World.

In order to lock the part to what I have now set things at I go to the Utilities Panel and select Reset XForm the click on the Reset Selected button. This modifier will make it as though the part was made in the current position, size and orientation.
Now go to the Modify Panel and Collapse the stack.
Now return to the Hierachy Panel and click on Affect Pivot Only again and in one of the side viewports move the pivot to the front edge of the rudder and restrict your movement to the viewports X axis. Zoom in as close as you can to accurately place the pivot. Since the rudder animation rotates the part around the parts Z axis we need to rotate the pivot so that the blue arrow representing the parts Z axis, lines up with the edge of the rudder. We are actually rotating the pivot on its X axis. Deslect the Affect Pivot Only button and your done. Because the rudder is a built-in animation, Makemdl.exe will insert the necessary code to make the rudder swing left and right when the model is compiled. These specific part names are listed in the MakemdlSDK and act as trigers or markers for Makemdl.exe.
Doing the Elevators, Ailerons and Simple Flaps are very simular with just possibly the added need to rotate the parts X axis to line up with the edge you are using as a hinge. These basic animations use the parts X axis for their rotation of up and down motion.
Propellers rotate around their Y axis. It is very important that you get the pivot located on the center line of the virtual crankshaft and the Y axis aligned with it. Don't forget to do it to all of your props and all versions, _still, _slow and _blurred. Once you have it done for one in a set, write the coordinates and angles down and then just type them in for the other two in the set.
As you can see by now this stuff is pretty easy. In the next article I'll get into some animations that are a little more complicated and we'll bring into the equation some new factors..... time and linking!