AC EVO v0.8: Full Changelog
CONTENT
KTM X-Bow GT2
KTM X-Bow GT4
Volkswagen Golf 8 R
Kyalami
 
GENERAL
external livery creation support
fix for crash when player is changing car setup while the session changes or restarts
added protection for controls listening while the session changes or restarts
fixed a crash when starting the game from a mapped network drive
fixed empty showroom showing briefly after launch before the splash screens
added numberplate selector in the paintshop for relevant cars
 
MP
possible crash fix when joining an MP server
server/MP chat: feedback after using admin commands
fix for a startup crash
fix for crash when failing to connect a server
fixed a crash when session switching while player is still loading the previous session
updated Ferrari SP3 gearbox sounds
MP: entrylist to allow defining starting order
MP: server launcher support for modded car content
MP: reject modified cars or incorrect mod version with sha check
fix for players being able to call the pause menu in MP while driving
fixed car receiving damage when spawning on shared box in MP
fixed freeze and crash when the player is spamming input during session join
 
GAMEPLAY
fixed hotstint game mode bugs with timing and results
fixed hotstint lap counter
fixed fuel still influencing pitstop time even if refuel amount exceeded tank capacity
fixed popup headlights not being synced with the gameplay logic
 
PHYSICS/HANDLING
removed rev limiter choking
telemetry laps enabled in Datsun default setup
DCT - added min filter throttle cut
Ferrari Daytona SP3 - restored launch control
rebaked dynamic track maps using revised logic
 
RENDERER
add projection correction
introduced supersampling
dynamic resizable texture pool and mesh streaming pool with real-time budget (this is used to keep vram within the available vram budget)
mesh streamer new logic
particles vram optimization
instanced skeleton optimization
enhanced vram reporting
add new vram usage category to keep track of the resources of the cars that are not streamed
clouds vram optimization
material aggregate heap vram optimization
readback passes vram optimization
esm vram optimization
buddy allocator peak stats
enhanced windshield rendering
update wipers refraction effect
added windshield raindrop splash effect
improved f+ tiled culling algorithm
hiz occlusion now uses reprojected view - this should mitigate flickering of trees and other objects that were cull-glitching
fix for early culling in mirrors when ultra setting is selected
fix tree popping in cockpit view on certain camera conditions
fix 9070xt and rx7600 recurring crashes
 
VR
hidden mask optimization
single pass stereo vr rendering
foveated rendering
pixel density slider (50% up to 150%)
custom vr resolve for msaa (reduced aliasing with spatial resolve with depth reprojection - do not use velocity or flags buffers)
world scale option
spectator window off by default and add an option to turn it on
prefer fps over latency option (similar to turbo mode of the openxr toolkit)
dedicated video settings file from vr - split video settings: vr uses vr.videosettings while the rest of the game uses video.videosettings
optimized vr pass by skipping passes if upscalers are not used
renderer draws straight into the OpenXR swapchain image (avoid copy opt)
added VR settings in the UI - the other non-VR settings are yet to be added
more aggressive foveating presets
eye tracked foveated rendering
fixed a few IQ problem
VR sunglasses option
 
GRAPHICS
race cars with plain liveries and material setup for external liveries
remapped cloud levels and aligned the graphics to the new physics ranges
aligned tarmac wet shader to new physics ranges
 
AUDIO
added timestamp comparison to collision event filter (fixes bottoming sound)
 
UI
fixed freecam widget not showing data when having the scene selector active in the showroom
numberplates - number type now includes cap to max digits
localization updates

Many of you have recently faced a "Content unavailable" message when trying to join an MP server. While initially it was a bug, now this is working as expected.
 
In essence, we have added a content validation check to prevent people from joining with altered original content.
 
Due to this change, any change to the content.kspkg such as unpacking it, repacking it, changing physics of a particular car or changing liveries through that route will lead to you not being able to join Multiplayer servers.
 
Please only use the officially supported routes for modding and liveries through the saved games folder.

Please only use the officially supported routes for modding and liveries through the saved games folder.

Back in EA 0.4 we tweaked around the root problems, which we couldn’t address at the time, but which gave a generally better, however still wrong result.
We traded inherent understeer for sensitive throttle pickup and an overall more "floaty" behavior, allowing and wanting a lot of slip to produce grip.  
 
Generally the perceivable problems trace back at least to ACC, if not even AC. So let's dive into what we were up to for this patch.
 
Disclaimer: All changes made apply solely to the GT slicks on cars from Mazda MX-5 Cup to Ferrari F40 LM, including all GT2, 3, 4 and Cup cars, but not F1 or road compounds.
You will likely want to start over with setups. Time permitting I will also update default setups - please bear with me.
 
Yaw Moment
Racing a car on and around the limit in tire research is an edge case. Yet, it's almost the only case we truly care about in a simulation, because this is where all the fun and frustration happens. Does the tire communicate with you, does it behave intuitively and reliably and does it do all these things correctly?
 
One of the most important edge cases is on race cars with a rear limited slip differential, that ties the rear wheels together on power to prevent energy being lost through the inside, unloaded wheel and instead drives the torque through the outside wheel. This difference in torque between the inside and outside rear wheel creates a "yaw moment".  
Think of it as putting a vertical stick through the center of the car from roof to floor. Then you go to one side of the rear bumper (say, right rear corner of the car) and push forward. At the same time imagine someone pulling on the left rear of the car. This force difference will rotate the car around the tooth pick in the center - does that make sense? I hope so.
 
Now, various effects have an impact on how much friction a tire produces and how much force it will be able to exert into the ground. Load, slip, camber, speed, temperature, pressure, toe... and countless other things. For the above yaw moment to take place, A LOT of things need to work exactly right. We have basically reviewed almost every factor involved and verified their impact on this particular edge case that makes all the difference to the behavior of the car. You will especially notice this in 1st to 3rd, sometimes 4th gear corners. Above that, the effect starts to wane as downforce increases the inside rear tire's grip and due to general performance degradation due to speed.
 
Response
The workarounds also forced us to use tires with rather high peak slip angles, which in turn results in slow response to steering inputs, as you first have to turn quite a bit to reach the peak grip of the tire. Also the rear end has to start moving sideways before it can produce the grip at higher slip angles. While the rear starts moving, the car’s inertia might be too big for the tire to catch it again when the slip angle finally reaches its peak grip, and the rear always remains in some sort of sensitive float and slide state.
 
Due to various improvements done, we were able to lower the tire's slip angle needs and as a result the response is much sharper.
 
Grip loss
Equally important as grip is not having grip, or rather, how you end up not having grip. The previous calibration led to overly lenient tires that would keep producing more grip the harder you drove over the limit, which made TC pointless and didn't penalize too much steering.
We have already worked in that area, mainly by adding dials and maths to better control the behavior of the slip/grip curves in various driving situations. This is not yet completed, but already better than before. You might still drive with TC off in Q, but in a race, I'm not sure if you would dare.
 
FFB
Changes to FFB really come as a side effect. But we have also made a tiny change to the scaling of the self alignment torque, which makes oversteer much more noticeable and generally provides higher FFB forces.Camber
Camber has various effects on the tire. It softens it, it increases lateral grip, it decreases longitudinal grip, it increases the tire’s response.  
Apart from solving a bug that led to the inside cambered tire to produce a lot of longitudinal friction, we now have separate impacts of camber on longitudinal and lateral grip, that we can also control individually. At least in some of my testing I found that you can feel the trade off with high cambers where you might gain cornering speed, but you also lose traction and braking capacity. We can now easily tweak this further. This marks a major improvement over ACC, where maximum negative camber was always the right path without any trade-offs.
 
Combined Grip
A lot of work went into shaping curves. How various effects impact one another, especially in regards to the famous "traction circle". Which just means: How much grip is still there longitudinally when you already request maximum grip laterally - and vice versa. Further, the tire does not only change its capacity, it also changes where this capacity is found. Higher load on the tire  shifts the peak grip to higher slip angles, the correct temperature makes the peak wider, speed makes the peak narrower and sharper, camber shifts the peak to lower slip angles.
We had several effects previously that shifted the peak further and further away, basically to unattainable slip levels, which led to a "more slip = more grip" sensation. This was, simply spoken, down to the grip/slip curve having an anchor in the far distance that wasn't moving down with the rest of the curve. We’ve thrown that overboard .
 
To make cars rotate with the 0.4 tire we had to resort to rather low amounts of combined grip. All changes done this patch contribute to us now being able to increase the combined grip again. Thus, the tire will offer a wider range within which it allows to tap into more longitudinal and lateral grip at the same time before giving in. This reduces the overall sensitivity on corner exits, and offers a more rewarding range to play with as you approach the limit.  
 
Contact patch
There's also a new logic that better accounts for contact patch variation in all situations. In any given situation the load spread on the contact patch has further influence on where the grip peak is found, adding to the overall dynamic of the tire. For example higher camber might make for a responsive tire, but in a low load situation the contact patch won’t be fully utilized and thus the camber offers less lateral grip than you expect. Only once load increases, the tire is deformed enough and the contact patch reaches optimal utilization allowing you to extract the most grip from the chosen camber angle. We think this might lead to tracks and car combinations where more camber will not automatically be the right choice, as the track profile does not benefit from always using maximum camber.
This likely needs further tweaking and we are looking forward to hearing your experience.
Overall the work on the tire for this patch has gone very deep and touched on the very fundamentals of the model in order to better understand its emergent behavior and to better review and debug the contribution of individual factors. We are much happier with this tire than previously, but work will always continue as there are still several topics that need review, debugging, decisions and ultimately implementation and testing. Among other things, we will keep reviewing the impact of tire pressures, temperatures and how they build, tire wear and various other parameters that can be summarized as damage to the tire like graining, blistering or flat spots.
 
Not only on tire level are we continuing to push forward. We are already experimenting with improved differential modeling and other drivetrain components, but are also planning to make adjustments to aerodynamic behavior or slip streaming. The variety of content we model often requires bespoke solutions for individual cars (e.g. torque vectoring algorithms or magnetic dampers) which leads to an ever increasing toolkit to accurately simulate the entire variety seen in automotive engineering.
 
A big thanks goes out to our physics programmer Fernando, who had to deal with me for months and rip the code apart time and time again and never flinched once.
 
We hope you like the improvements and continue to provide bug reports and feedback in order to push and expand the limits of our physics engine