PrismTextureStreamer

A Prism3D plugin that takes over cabin screens (GPS, dashboard, or any custom accessory) in Euro Truck Simulator 2 (or American Truck Simulator) and mirrors a live captured window onto them.

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What it does

Press Ctrl+F8 in game to open an ImGui overlay. From there you can:

• Add a GPS screen, Dashboard screen, or a Custom screen (The target .tobj MUST be a functional screen from a UI Script, such as /ui/gps.sii)
• Pick a running application window as the source for that screen
• Adjust target resolution and framerate
• Apply changes

Whatever's rendering in the picked window gets captured and blitted onto the truck's screen every frame.

How it works

1. Redirecting the texture file

A hook on Prism3D's memserver_texture_queue_processor walks the engine's pending texture object queue every tick. If a queued tobj's path matches a screen's original_texture (e.g. /vehicle/truck/share/gps.tobj), the path is swapped for override_texture before the engine loads it.

2. Catching the texture at creation time

The override .tobj still gets built into a real DirectX texture eventually, there's a hook on ID3D11Device::CreateTexture2D. Every creation call is checked against a fignerprint. The real game textures never match the fingerprint, so it's whats used to capture the screens texture.

This method is a bit "jank"... but it does work ;)

Once matched, the description is rewritten before the real CreateTexture2D is called:

D3D11_TEXTURE2D_DESC modifiedDesc = *pDesc;
modifiedDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
modifiedDesc.Usage = D3D11_USAGE_DYNAMIC;
modifiedDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
modifiedDesc.MiscFlags = 0;
modifiedDesc.Width = screen.targetLiveTextureWidth;
modifiedDesc.Height = screen.targetLiveTextureHeight;

This gives us a CPU writable arbitrarily sized texture instead of the default game texture - then the resulting texture and its immediate context are cached on the screen_t for later.

3. Feeding it frames

Every present call, each screen with a live texture and an active source:

• Pulls the latest RGBA8 frame from its content source
• Map()s the live texture with D3D11_MAP_WRITE_DISCARD
• Copies row by row using nearest neighbor sampling if source and destination sizes differ, with an optional vertical flip
• Unmap()s it

4. Forcing the screens to actually render

The GPS/dashboard/custom screens are normally only drawn under specific in game conditions. dllmain.cpp patches the relevant conditional jump in the games process, flipping JE to JMP (and back) at runtime so the screen's render path is unconditionally taken whenever a screen of that type exists, and restored to normal when it doesn't. Addresses are found via pattern scanning, so it hopefully survives most game updates.

Content sources

Currently there's one source implementation, WindowSource, which finds a target window by executable name, then captures it every frame using PrintWindow + GetDIBits on a dedicated worker thread.

The source uses a interface IContentSource, so other backends (a video file source, a mintor source, etc) can be implimented very easially in the future without touching the DX11 or menu code.

Requirements

• MinHook
• Dear ImGui
• SCS Telemetry SDK
• DirectX 11

Known issues

• Fingerprinting textures by dimensions/format means any other texture in the game that happens to match GPS/dashboard's size and format exactly would get caught too which is unlikely (if using unqiue dimentions), but not impossible.
• Custom screens have no override_texture_size_w/h wiring in the menu yet, unlike GPS/Dashboard.

Usage

1. Drop the compiled plugin DLL into your ETS2/ATS plugins folder (not a injected DLL)
2. Launch the game, Ctrl+F8 to open the menu
3. Add a screen, pick a source window, hit Apply

Contributing

PRs and issues are welcome, keep in mind:

• If a pattern scan fails to resolve on a newer patch, that's the first thing to check before assuming something else is broken. (Same with any Prism3D structures inside prism/prism.h)
• DO NOT use hard coded file offsets etc, keep with using pattern scans where possible.
• If you're adding a new IContentSource (video file, monitor capture, etc.), implement it against the existing interface in sources/content_source.h.
• Match existing code style so diffs stay reviewable and the project isnt a mess of multiple people.
• Test on an actual ETS2 install before opening a PR.