Hi all,

Sorry for the wait! This was a tricky one

There's an experimental build of 0.2.51 up on the experimental branch

This time powertrain and track behaviour have seen a full overhaul.

Main Changes

• The powertrain simulation is now much more realistic.
• Moved the track simulation off of PhysX into an in-house solution. This allowed for in-depth rolling resistance and bump-stop simulation and paves the way for more factors like weight dispersion to be simulated. This moves a lot of the physics work onto other threads.
• Track collisions are now belt-based instead of wheel-based. Allows the belt under the sprocket and idler to provide traction and suspension.
• Added a new traction model. It's now more realistic and allows track slipping, skidding and drifting.
• Clutches are now more realistic, with a maximum torque transfer and slippage.
• The clutch is now disengaged during gear shifts.
• Track belts now have every joint simulated and more accurate collisions with the wheels. Belts can now detach from the wheels instead of being anchored to them.
• Destroying tracks now causes their belt to break. Instead of the placeholder 'belt vanishing'.
• Suspension now simulates bump-stops. When a suspension's travel is maxed-out, its bump stop applies strong forces to prevent damage.
• Added microbumps to the ground. This simulates small (<5cm) irregularities in the ground. This is returning after it was cut due to optimization issues, it's optimized now.

Other changes

• Torsion bars now have more realistic stiffness and travel.
• Suspensions are now preloaded so that the vehicle sits at the target-angle (previously called rest angle). When the vehicle is off of the ground, suspension arms will extend down more than before.
• Artificial physics constraints no longer need to be applied to the vehicle at rest, resulting in more realistic recoil when firing while stationary.
• Twin transmission: The driver will no longer shift down more than 2 gears to steer while holding the throttle, 4 while the throttle is released at speed.
• Fixed track wheels jumping when moving from a stand-still.
• The final drive property has been moved from the transmission to the sprocket wheel.
• The vehicle's powertrain speed limit is now shown next to the final drive property.
• Key powertrain simulation variables are now shown in the movement info screen 'V'.
• The driver now revs to an operating engine RPM when moving from a stand-still. This operating RPM is 50RPM over the target min.
• Vehicles now launch on 2nd gear when starting on inclines below 5 degrees.
• Brakes are no longer automatically applied above 5km/h, allowing you to cruise.
• Switching between drive and reverse now requires the vehicle to come to a near complete stop.
• The driver no longer upshifts on inclinations above 10 degrees.
• The driver no longer upshifts when turning.
• Suspension damping is now editable in WWI
• Raised minimum torsion bar diameter from 20 to 30mm.
• Raised minimum damping from 0.
• Improved motion blur on fast moving tracks belts.
• Smoothed suspension test bumps
• The sprocket wheel is now classed as 'powertrain', and is visible in interior view. This provides easier access to the moved final drive.
• Wheels no longer visually decouple from their suspension arms under high load.
• Volute spring constants are now much closer to real values and scale more realistically.
• Torsion bars can no longer be longer than the track separation.
• Torsion bars now only offset one track if their length is above half the track separation.
• Fixed the long-standing bug of vehicles jumping when exiting photomode. Photomode no longer scales the physics sample rate with the timescale. So slower timescales won't affect the physics sim.
• Vehicle movement is now smoothed between physics updates. So if you run the game at over 100fps, you should see smoother movement and better motion blur.
• Transmission aux gear ratio now disabled by default.
• Leaf spring stiffness is now significantly higher than before.

Optimizations

• The bulk of the movement system is now multithreadded.
• Significantly optimized CPU-side rendering of track belts.

Known issues

• Belts can clip through objects above them like fenders.
• The modded invisible track segment part used for wheeled vehicles causes a crash.
• Modded multi-tracks are broken.

Overall this update aims to:

• Make all vehicles feel heavier, like you're driving a real tank.
• Make light vehicles more viable by increasing the difficulty of designing manoeuvrable and well armoured vehicles (while still allowing heavy vehicles to have high top speeds).
• Make suspension setups and track layouts affect vehicle behaviour more.
• Fix several long-standing movement bugs.

Give it a go and let us know what you think!

- Hamish