I am trying to calculate angular deceleration of object caused by inertia, but I don't know. I have access to objects inertia and current angular velocity. How do I calculate angular deceleration?

Uh... And what could cause angular deceleration?

Friction, drag, etc.

Can you give me equations for at least the 2 ones?:D

A set of useful formulas:

w = w0 + a * dt

w - angular velocity

a - angular acceleration

a = T / I

T - torque

I - moment of inertia

In 3d case, I would inertia tensor(matrix) and formula would be different, in physics engines it usually handled in a special way and inertia tensor is represented as vector.

the origin of the torque can be a force applied not directly to the center of mass of the body (suspension force, friction force, engine thrust and etc.)

T = F x R

F - force vector

R - is a vector from the center of mass to the point where force is applied

Hope this helps.

Yeah, but I need to find out not the accelerative, but deccelerative torque. A torque that resists turning.

Torque in opposite direction give you angular acceleration in opposite direction. The "a" in first formula can be negative.

Yeah, but I need to find out not the accelerative, but deccelerative torque. A torque that resists turning.

When? Under what circumstance do you want a deceleration? Is this just general damping, or like some kind of drag force? There's a lot of was to cause a deceleration ranging from very complicated to very simple, and which one gets picked depends on what is needed. So, what do you need, and why?