Byte Insight
iRacing Graphics Setup.
My Sim Racing and in particular iRacing career started on a ROG STIX 3070 with 4K TV before proceeding to VR with some HP Reverb G2s. Getting the best from the latter is not a plug and play task. To make matters worse the human response to underperforming VR is less forgiving than straight screens.
I’m no expert on the hardware market – I have a reasonable understanding of classic hardware fundamentals as taught in Computer Science 101 but that’s the ceiling. In this post, I’m trying to explain how I understand it from my own recent (March 2023) shopping experience. As I have the Reverbs on Nvidia Chips there will be a slight lean in that direction but I believe much is applicable to straight screens and other GPU chips.
It might help to consider some approximate pixel values for a moment:
- HP Reverb G2s – 2160 pixels squared per eye – 2160 x 2160 x 2 = 9331200 pixels
- Triples on Full HD – 1920 x 1080 x 3 = 6220800 pixels = 67% of VR
- Triples on 4K – 2560 x 1440 x 3 = 11059200 pixels = 119% of VR
- G9 Super Wide Screen – 5160 x 1440 x 1 = 7430400 pixels = 80% of VR
But this is not the full picture as frame rates per second (fps) are the real VR killer or sickness inducer. Personally, I notice it around the 70fps mark with one slightly slow to respond eye but other racers tell me they are okay down to 50/60 fps. The point is that in VR with no real world reference points when your virtual world starts to stutter your brain has no reference point to work with and then you start to feel sea sick. Its worth noting that a fan blowing on the face as really helped me in VR in general and during longer races but we diverge.
New GPU Time?
Hold on – its not all down to the GPU – the CPU does some heavy lifting as well! The actual numbers here are very game dependant. Some games are better at utilising multiple cores/threads than others. iRacing is renowned for running on limited cores/threads due to the age of the engine. However, a visit to the Gaming Bottleneck Calculator can show us how different combinations of CPU/GPU might perform in iRacing. Although unfortunately we have to use Assetto Corsa as our test game for these calculations below.
| CPU | Resolution | Pixel Count | 3070 | 4080 |
|---|---|---|---|---|
| i9 10850k | 2560 × 1440 | 3686400 | -36.7% CPU | -77.3% CPU |
| 4096 x 3072 | 12582912 | -34.2% GPU | -2.6% CPU |
What’s noticeable in the table above is that as our resolution reduces we are placing higher demands on the CPU and its there the bottleneck occurs. I’m told this is due to increased FPS but cannot support that with evidence (readers – help me out here).
Note in April 2023 – 8GB V-Memory is the maximum IRacing can use.
In Game Analysis of CPU/GPU Bottlenecks
If we look at the Frame Rate Meter in game in order to sustain 89/90fps we need:
| LABEL | MEANING | SOLUTIONS | OPTIMUM |
|---|---|---|---|
| R | Rendering. The time (ms) it takes for the renderer to process a frame. | Adjust factors such as Shadows, Cube Maps, HDR, and object detail which mainly rely on the CPU. | [11] (ideally 5.0 or lower for full-field and start of a race) |
| G | GPU Frame Time. The time (ms) it takes for the graphics card to draw a frame. | Adjust factors such as HDR, Antialiasing (AA), mirrors, sharpening, heat haze, and distortion that mainly rely on the GPU | [<5] (ideally 5.0 or lower for full-field and start of a race) |
| T | Total Time – Renderer to GPU completion. Not same as R+G | See R & G | [12.5] |
| C | Physics Thread. | See R but also number of cars drawn. | [3.5] Needs to be run 60 times a second to keep the user up-to-date with what is happening in the sim. |
| S | Skew is the amount of delay currently in the physics system | See R & C. | [0] |
| P | Page Faults | [0] |
If R is higher than G it would indicate a CPU bottleneck and if G is higher than R then a GPU bottleneck. However, the Reverb G2s max at 90FPS. 1000 ms / 90 frames = 11 so G cannot reasonably drop lower.
There are 1000 milliseconds in a second. If the Physics thread needs to run 60 times a second this is once every 16.7ms.
Which GPU?
The other thing that complicates any new GPU purchase is that series and models are not linear in their performance growth. That is to say a 3080Ti might be a better purchase than a 4070Ti as shown below. I really wish I could find a link to the screengrab below but you can compare all the chip specs on the Nvidia Comparison Page.
I’m also going to add that there are people in my league discord doing very well in both lap times and race craft running 2080 cards on 27″ 1080 Triples. So I’m definitely of the opinion that its not about having the latest kit but its about having the right kit working in harmony with optimised settings. Unfortunately, as I found out recently cheaper older and very suitable kit sometimes just isn’t available to buy or doesn’t represent good value for money in the long term when you consider warranties and investment.
Tuning your settings
Okay, so you have got your GPU and visual output of choice so now to the tuning. The iRacing Forum has a whole section on technical aspects and in particular has one dedicated to VR. Within this section there are some superb nuggets that would help anyone optimise their graphics regardless of VR or screen.
In particular the VR optimisation guide is helpful as it details whether something is CPU or GPU demanding and to what extent. The following table is a quick reference sheet based on that guide. This is not my work and full credit goes to Robert Ehrling who did all the original experimenting. The guide was last updated in Oct 2022 so hopefully a lot is still relevant.
| Description | Action | CPU/GPU | Notes |
|---|---|---|---|
| Resolution | Low as possible | ||
| Res Scaling | Leave Disabled | ||
| UI Zoom | Personal | ||
| Full Screen | Personal | ||
| Border | |||
| Enable SPS | (VR) Enabled | ||
| Align | Personal | ||
| Reflex | Enabled with Boost | Nvidia specific feature | |
| Gamma, Brightness, Contrast | Personal | ||
| Sky/Clouds | Low Setting | Mainly CPU | Medium to high performance impact. |
| Cars | High Detail | CPU/GPU | Drop to Medium if frame rate reduces. |
| Pit | Medium Detail | CPU/GPU | |
| Event | Low Setting | Mainly CPU | Medium to high performance impact. |
| Grandstands | Low Setting | Mainly CPU | Medium to high performance impact. |
| Crowds | Low Setting | Mainly CPU | Medium to high performance impact. |
| Objects | Low Setting | Mainly CPU | Medium to high performance impact. |
| Particles, Full Res and Soft | High Setting | CPU/GPU | LMH all. Performance impact evenly. |
| – Full Res | Tick | Gain frame rate | |
| – Soft | Un Tick | Lose frame rate | |
| Max Cars | 40/Personal | CPU/GPU | LMH all. Performance impact evenly. |
| – Draw Cars & Pits | Default | Lowering these can be an easy fix for better performance | |
| Dynamic LOD, FPS, World and Cars | Default | Mainly CPU | Low to medium performance. |
| Frame Rate / Vertical Sync | N/A for VR | This is fixed in VR | |
| Max GPU Video Memory | Personal | Set this limit to our GPU video memory capacity and reducing that with around 2000MB or more to get a proper value. | |
| Max System Memory | Personal | Maximum setting here is 16384MB. I would suggest that if you have 32GB for the system then 16GB for iRacing is ideal. | |
| Anisotropic Filtering | 16 x | CPU/GPU | Low performance impact. |
| AA Samples | 2x & 4x | CPU/GPU | Medium, high to very high-performance impact. |
| Render Dynamic Track Data and Render Dynamic Tire data | Enabled | CPU/GPU | Medium to high performance impact |
| Shadow Maps Cloud Shadows | Off | CPU/GPU | Medium, high to very high-performance impact |
| Objects Self Shadowing | Off | CPU/GPU | Medium, high to very high-performance impact |
| Night Shadow Maps, Walls and Headlights | Disabled | CPU/GPU | High to very high-performance impact |
| Cockpit Mirrors Max | Set to 2 | CPU/GPU | High to very high-performance impact. |
| Higher Detail In Mirrors | Disabled | CPU/GPU | Very high-performance impact. Frame rate killer |
| Headlights | Low Detail | ||
| Headlights on track in mirrors | Disabled | CPU/GPU | Low to medium performance impact |
| Virtual Mirror FOV | Personal | Many VR users report that a FOV number around 45 | |
| Motion Blur | Off | ||
| Anti-Aliasing | Disabled | Mainly GPU | LMH performance impact. |
| Sharpening | Enabled | Mainly GPU | Low to medium performance impact. |
| HDR | Disabled | CPU/GPU | Medium to high performance impact. |
| Video Mem Swap High-Res Cars | Disabled | ||
| 2048×2048 Car Textures | Enabled | ||
| Hide car numbers | Personal | Only applicable in test sessions. | |
| Distortion | Disabled | Mainly CPU | Low to medium performance impact. |
| Heat Haze | Disabled | Mainly GPU | Medium performance impact. |
| SSAO | Disabled | Mainly GPU | Very high-performance impact |
Notes about Nvidia 3D Settings.
If you are upgrading or making changes iRacing recommends doing a default restore of the settings in case an old setting is holding back performance. Ideally you want to update your driver with a clean install. Do not install GeForce!
- Right-click desktop and go into Nvidia Control Panel
- Click Manage 3d Settings
- Click restore to set everything to default for global settings or program settings
- Select iRacing from Program Settings and make the following changes.
- Anti-Aliasing – Transparency: change to Multisample.
- Power management mode: Prefer maximum performance
- Vertical Sync: Off
- Virtual Reality pre-rendered frames: …. change to 1 (higher numbers have more latency 2 or 3).
