Cars_Animation_Tutorial.pdf

BLENDER TUTORIAL

- Automated animation for cars -

Animating one car on a straight road is easy, but if you want to animate one or several cars

following a curve, with speed variations, and other refinements, you will need a method

allowing automatic steering and proportionnal speed for the wheels rotation.

This tutorial will show up how to make automated animations for cars.

Your car trajectory will be a nurbs curve ( Fig. 1-2 ).

A bezier curve could do the trick, but Nurbs curves are easier to manage with. I say a

trajectory instead of a path, because we will not use it as a real Path. Generally, a Path curve

has a speed Ipo, and plays the animation on a fixed number of frames. The method that I

want to show you, uses a more flexible way in my opinion.

Later, in your animation, you will need a car body. For now, it is not necessary, and you only

have to know that all car bodies you could model will be easily parented to the system that

we will build now.

You only need to model one wheel, and duplicate it four times. The front wheels will remain

free, and the rear wheels will be joined in one unique object.

It is important to put the center of each object exactly at the center of each mesh. So, each

front wheel will have it’s own center, and the rear wheels will have their center at half

distance between them.

The distance between the front and rear wheels is not too important right now, and it will be

adjustable later to the dimension of the car bodies that you will use.

You will need a Mesh that will be used as a Chassis to parent the wheels and the body. As

this object will not be rendered, you will set for it an unvisible material, or a bound box. You

could also use an empty or even a bone, but a flattened cube will be visually of a better help.

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- Automated animation for cars -

Fig. 3 shows the wheels and the Chassis object. The Chassis will not be rendered, and will

only be used for parenting parts like the wheels and the body. It can also be seen as a place

holder for the body during the animation setup.

Fig. 3

Before parenting things, you will have to be sure that all the object have their axis oriented in

the same direction, so apply CTRL-A to all of them. This is very important if you don’t want

to fight with rebel objects later !

An other mesh will be necessary. This one will also be unvisible at rendering, but is very

important for the animation. This mesh, that we’ll call Arrow mesh, because of its shape, will

be the core of the animation ( Fig. 4 ).

You have to choose

a starting direction for your animation. In this example, I have choosen the X axis.

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- Automated animation for cars -

For the Arrow mesh, you can start with a single plane that you will duplicate to get a small

square face centered at half distance of the rear wheels, an other one at half distance of the

front wheels.

These two groups of vertices are the references for the animation. We’ll see later what they

are exactly used for.

You can add several other groups of vertices, that will be used as helpers for the animation.

The front end of this mesh will be an arrow head shape, and you can add a tail made of

several square faces. the Arrow mesh is shown in green color on Fig. 4 .

As we might need to select the Arrow when the car body will be present, the head and the

tail of the Arrow mesh will be used to select easily the Arrow mesh when we’ll set up the

animation.

Now, we are going to add the curve, so add a Nurbs curve in top view, and draw the

trajectory of the car by adding as many dots as necessary.

In edit mode, select the first dot of the Nurbs curve, and by SHIFT-S, then Snap Cursor on

Selection. Make this location the center of the Curve Object. As Nurbs curve don’t extend

themselves until the extreme limits, you can add more dots close to the center of the Curve

object, to see the starting tip of the curve.

Your curve will have to be in straight line in the X direction (the direction choosen earlier),

in its starting part, in order to be able to set up correctly the rigging of the car parts ( Fig. 1-2 ).

The easiest way to start drawing the curve is to resize it by 0 in Y direction to get the straight

part, and once you have set the first dot on the left as the center of the curve object, you

extrude the curve from the right side by selecting the dot and using CTRL-LMB.

Be sure that your curve and your arrow have their axis in the same direction by applying

CTRL-A.

Now, we have to link the arrow to the trajectory. Select the Arrow Mesh, and add a Curve

Modifier. Name it Curve, as it is the default name for the curve you have added.

Don’t be afraid, the Arrow will turn of 90°, and its center will get out of the arrow mesh and

will be displaced on the center of the curve. It is normal.

Now, rotate the Arrow of 90° to match the Curve direction. If you select the arrow, and move

it along the Y axis by G-Y, you will see your Arrow moving and bending along the curve.

Apply CTRL-A to your Arrow mesh again.

At first glance, it might be surprising to see that you have to move the Arrow mesh along the

Y axis to start a displacement in X direction, but from now, you must understand and keep in

mind that the straight displacement of the Arrow center along the Y axis represents the

displacements of the Arrow mesh along the curved trajectory. This is very important, because

you will be able to drive your car with only One Ipo curve (Loc X,in this example), and make

speed variations as well with this only curve ( Fig. 6 ).

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- Automated animation for cars -

You can also notice that in Edit mode, the Arrow mesh is rotated. This is because you have

rotated the Mesh in object mode. As in Edit mode the Curve modifier is not applied, the mesh

appears rotated. This has no importance, and will not be a problem when you will have to

edit the mesh later.

Now, open an Ipo window. Select the Arrow mesh, and insert a Loc Key at frame one. Go to

Frame 100, or any Frame number matching the animation time you want, and move the

Arrow center along the Y axis, until the arrow mesh reaches the end of the curve. Then, insert

an other Loc Key. As only the Loc Y Ipo is interesting, you can delete the Loc X and Loc Z

Ipos.

You can set the Y Loc Ipo to linear or Bezier as you want. For the first settings, a linear curve

in suitable.

Troubles ? If you have done something wrong, you might notice that the axis direction of

your Arrow mesh is different than the axis direction of the Curve, and the animation now

doesn’t follow the curve. Instead, the Arrow moves along Y direction. If this appens to you, it

can be easily corrected either by applying CTRL-A to your Arrow mesh. You may also need

to play in the Ipo window, by replacing the Loc Y curve by the Loc X curve, using the buffer

(Buttons with yellow arrows).

If you want to rotate the scene of 90°, you have to rotate only the Curve around its center,

and apply CTRL-A to it, and everything will work correctly. Any other angles are also

usable. This said, it is safer to keep the original direction, if you can.

Go back to Frame 1.

Now we have to take care of the rigging of the car parts themselves.

We will need 3 Empties. ( Fig. 7 ).

One is named

Empty Rear .

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- Automated animation for cars -

It will be the rear tracking reference for the Chassis. This Empty will be Vertex Parented to a

square face of the Arrow mesh, placed exactly between the rear wheels. This Empty will be

the warranty that the trajectory will pass exactly in the middle of the rear wheels. This Empty

will be animatable later with a dLoc offset value, if you want to add a skid effect on the rear

wheels.

The second Empty is named Empty Front. It is Vertex Parented to a square face of the Arrow

mesh placed exactly between the two front wheels, in the same way you parented the Empty

Rear.

The Chassis mesh has its center placed exactly on the Empty Front and is parented to it. This

allows it to rotate around this Empty.

The chassis has a Track To constraint aiming the Empty named Empty Rear. ( Fig. 8 ).

As the car body will be parented to this Chassis object, the car body will always be right on

the trajectory.

The third Empty is named Empty Steering. This empty will be used to copy the Z rotation of

the Empty named Empty Front, and to tranfer this rotation to the Front Left wheel. Empty

Steering will be parented to the Chassis. As said, it has a Copy Rotation Constraint, copying

the Z rotation of Empty Front. ( Fig. 9 ).

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