bulletphysics
Fix incorrect linear velocity of the vehicle chassis
When the vehicle is completely stationary its linear velocity obtained with getLinearVelocity in Y axis is always positive and quite high i.e. 0.15. That's not any oscillation but a steady value of a stationary body. I noticed that getCurrentSpeedKmHour is not equal to getLinearVelocity.length() * 3.6 when the simulation step is finished, it only is equal when m_currentVehicleSpeedKmHour is being stored. After some investigation I found that impulses added to the vehicle body by the suspension are not being processed until the next simulation step. This change allows the linear velocity to be reported correctly. It may also reduce input lag by one step. I'm only not sure if updateActions shouldn't be even higher. Being above integrateTransforms is enough to fix the linear velocity issue.
Actually this PR fixes one thing but breaks another. It makes the wheels lag behind the car by 1 frame. To make this work updateActions need to be broken into two parts. One updateActions, before integrateTransforms and then updateActionsIntegrate, which will only update the wheels' positions. This will fix incorrect linear velocity of the body and won't cause the wheels to lag behind the car.