Controlling Velocity and Spin

The simulation system of Realsoft 3D controls objects using two properties: velocity and spin.

Force fields, such as gravity and electro-magnetic fields, modify velocity and spin properties according to the laws of physics. In collisions, velocities and spins change according to rebound energy, mass momentum and other physical properties of the colliding objects so that the objects will rebound correctly.

In addition to force fields, the user can also control the spin and velocity. There is nothing exceptional in these attributes. You can define and even key frame them as you like.

In many situations, it is necessary to define initial velocity and spin for animated objects. For example, when building a bowling simulation, the bowling ball needs an initial velocity.

To define a constant velocity for a sphere:

1. Make sure the root level is 'Simulated' and create a sphere.

2. Select 'Tools/Simulation/Define Velocity' from the menu bar.

3. Enter two points through a view window. The two points define the speed for the object - in other words - how much the sphere will move in one second.

You can also make the sphere spin: select the sphere and the menu 'Tools/Simulation/Define Spin'. Enter three points through the view window: center, start angle and end angle.

The spin tool renders a 'helix' to indicate the angular velocity. The object will rotate this much in one second. (Note - one can set multiple rotations.)

Defining spin

You can also define the velocity and spin attributes numerically. To do this, select the sphere and open the property window. Then go to the 'Phys' tab and enter the desired values to the 'Velocity' and 'Spin' fields.

Defining velocity and spin numerically using the property window