Fan research vs official fix – EA Sports WRC decal rendering on GeForce GTX 10 series cards

December 22, 2023

4 min. to read

• Introduction
• The official fix
• Other fixes in the v1.4.0 update

This article is a follow-up to Fixing EA Sports WRC decal rendering on GeForce GTX 10 series cards.

Introduction

On December 14, 2023, Codemasters released the v1.4.0 update for EA Sports WRC. Among countless fixes, two items align with the fixes previously published in SilentPatch:

• Fixed an issue where Fanatec and location event plates would appear stretched when using NVIDIA GTX 10 series GPUs.
• Fixed an issue where framerate would drop to below 10 fps when using the Livery Editor on NVIDIA 10 series GPUs.

This was somewhat expected, since by the time I released SilentPatch last month, I’ve had the opportunity to get in touch with Codemasters and share my findings in as much detail as possible. I was later informed that the issue was fixed internally and was given an OK to publish SilentPatch as a stop-gap solution for the affected users. My efforts have also been highlighted on the official EA Sports WRC Discord 🙂 In the end, everyone won.

With this out of the way (and with SilentPatch officially deprecated), I was curious about the approach used for the official fix. In this short article, I’ll dissect the official fix and compare it with mine.

The official fix

Let’s start with a recap. When I figured out the root cause of the original bug, I outlined two possible approaches that could be taken here:

1. Make the SRV typeless by defining the stride explicitly and setting the format to DXGI_FORMAT_UNKNOWN. This approach does not require modifying the shaders.
2. Modify the shader the same way I did, replacing StructuredBuffer<uint> with Buffer<float2>. This way the shader handles the existing input buffer layout correctly, regardless of the GPU vendor/generation, and a current way of accessing the buffers is used.

In my fix, I went for the second approach, because replacing shaders is a much easier task than tracking down specific resource creation. However, I was under the impression that the official fix would adopt the other approach, as that would’ve fixed all similar broken cases. Surprisingly, I was wrong – with the v1.4.0 update, the buffer definitions remain unchanged:

Notice that the resources still have a defined format and are not UNKNOWN.

Instead, automatic variable names from RenderDoc immediately show that Codemasters changed the shaders themselves – in v1.3.0, the automatically generated name of the first bound resource was structuredbuffer0, in v1.4.0 it’s texture0, indicating that the way the resource is accessed by the shader has changed!

Indeed, looking at the shader assembly of the fixed shader, it now looks identical to the shader from SilentPatch – which means my suggested solution of changing the shader inputs was used as-is:

   imad r0.x, v1.x, cb0[1].x, cb0[1].y
   ld_indexable(buffer)(float,float,float,float) r0.xy, r0.xxxx, t0.xyzw
   mov o3.xy, r0.xyxx

Is this the best solution? I can’t say this with absolute certainty of course, but I am somewhat surprised at the approach taken. However, the other solution (making the buffers typeless) may have introduced problems with other shaders, so perhaps the current solution was thought of as the safest.

However, I have a few more points to raise about this fix. It technically is complete, but it could have been done better, as I believe the current solution is not complete, and DirectX specification is still violated by those shaders:

1. texture1 is of type R8G8B8A8_SNORM, but the shader accesses it through Buffer<float4>. If my knowledge of HLSL is correct, the sampler used here should have been Buffer<snorm float4>.
2. structuredbuffer2 and structuredbuffer3 still use StructuredBuffer<> samplers, despite those buffers not being typeless. In an ideal case, they should also have been changed to use Buffer<>. This is most likely a violation of the DirectX spec.
3. texture0 is of type R16G16_FLOAT, therefore the shader could have leveraged GPU’s support for 16-bit floating point values if the resource was sampled as min16float2. This type combines compatibility with specialization – as it leverages native support for half-floats on supported hardware, and falls back to full floating point values otherwise.

Other fixes in the v1.4.0 update

The changelog of this update is massive, but I’d like to highlight two other things:

1. Aside from the aforementioned changes, the Livery Editor performance is now improved on all PC configurations. Before this update, the editor was slow for everyone since the game was re-rendering all decals to an 8192x8192 render target every frame. In v1.4.0, this is only done when the decals are added/removed/moved/scaled.
2. This update introduced the Central European Rally, a new location in the Czech Republic. Unfortunately, this has introduced a critical issue with the existing Career Mode saves, making saves from further WRC seasons unusable. This is a gameplay issue that in a game of this scope is effectively un-fixable from the outside, and the fix addressing it is scheduled only for mid-January – so it’s a bummer 😔

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