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?

Angular deceleration caused by inertia is zero. Easiest formula ever!

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?