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A per-draw CPU profile of a real Minecraft frame (perf on the render thread, which sits at 100% of one core on both backends) said the deficit is translation overhead, not the GPU, and named where it goes. This removes the largest items it found, on both backends and in the shared frontend they both feed. The single biggest one was not translation at all: IsBackendContextCurrentOnThisThread called eglGetCurrentContext on every invocation, and glvnd answers that with a getpid() fork check - a real syscall. The predicate sits two and three deep in every draw (the deferred-release drain, the global-UBO ring availability check, and the ring allocation), so it accounted for 16.3% of the render thread. EGL is still the ground truth, but re-verifying it once per thread per frame catches an external migration at the next frame boundary rather than the next call, which recovers the same bookkeeping. Texture uploads now carry a dirty region instead of a per-level flag. Minecraft animates atlas sprites with 16x16 glTexSubImage2D calls into a 1024x512 atlas and respecifies the lightmap every frame; a per-level flag turned each of those into a full-level re-upload - about 3.6 MB a frame of texels nobody changed. MipmapStorage accumulates the written box, Espryt uploads it with UNPACK_ROW_LENGTH striding into the level shadow, and Magma stages just that box. The box is a union, not a range list: repeated writes to one level widen it and it degrades to exactly the old whole-level upload, which is the honest worst case. glBufferData(NULL) is the orphaning idiom, and the backend was answering it by uploading the stale CPU shadow - turning a rename the driver does for free into a full synchronized upload. BufferObject now records that a NULL respecify leaves the store undefined, and the upload is skipped until content is actually written. The rest are smaller and of a kind: the deferred-release queue is probed without taking its mutex, the UBO ring waits on the frame fence that frees the space it needs instead of draining the whole pipeline with glFinish at the size cap, VAO binds go through a shadow so a draw's second bind of the same object does not reach the driver, the per-draw clean-texture probe short-circuits on the content version before rebuilding shape info, glUniform drops byte-identical writes (which otherwise dirty the whole UBO for the next draw), re-binding the texture or VAO a slot already holds no longer bumps the generation counters a backend fast path is keyed on, and the texture validators stopped taking shared_ptr by value. On Magma: descriptor-set reuse keeps four entries instead of one, because draws alternating between two programs - the chunk/entity ping-pong - thrashed a single slot into a full re-allocate and re-write every draw; a DynamicDraw buffer whose contents survive two frame boundaries is promoted to resident storage instead of being re-copied into the per-frame arena forever; and sampled-read barriers name only the shader stages whose device feature is enabled, which also removes a latent VUID violation (ALL_GRAPHICS names geometry and tessellation stages a device need not have). Measured with the Minecraft rig (render distance 32, p50 fps, same machine, single sample each): vanilla 1.21.1 Espryt 10.8 -> 36.3 and Magma 31.3 -> 44.6; 26.2 snapshot Magma 114.5 -> 210.5. Fabric+Sodium moved inside noise on Magma (854 -> 766) with the native baseline itself moving 838 -> 1031 between the two sessions, so treat that cell as unresolved rather than a regression measured. Unit tests 421/421. The CTS A/B was not run: these numbers and the test suite are the whole of the evidence, and a conformance regression would not have been caught here.
MobileGL
A desktop OpenGL implementation
MobileGL is a free and open-source project that implements a desktop OpenGL API. The goal is to provide a complete desktop OpenGL implementation with a state management layer and multi-backend support.
Note
Status: In development. Parts of the codebase are incomplete. Current short-term target: OpenGL 4.2 (Core Profile).
Project positioning
MobileGL is an implementation of a desktop OpenGL library. It aims to provide:
- Full OpenGL state management.
- A front-end that exposes OpenGL functions.
- Multiple independent backend implementations, where each backend targets a specific graphics API and remains fully isolated from others.
This project is intended as an implementation/translation layer.
Key components
The repository is organized into following top-level modules:
- MG_State — state tracking and management logic for Graphics APIs.
- MG_Impl — front-end implementations of Graphics APIs that interact with
MG_StateandMG_Backend. - MG_Backend — per-backend translation layer that maps front-end Graphics APIs' semantics and state into concrete backend API calls (e.g. OpenGL ES, Vulkan).
- MG_Util and other utility modules.
Third-party components
MobileGL reuses several open-source projects:
- SPIRV-Cross by KhronosGroup - Apache License 2.0: github
- glslang by KhronosGroup - Various Licenses: github
- DiligentCore by Diligent Graphics - Apache License 2.0: github
Refer to each component's repository for exact license texts. Any bundled third-party code in this repository is included under the upstream project's license.
Compatibility & target
- Short-term target:
OpenGL 4.2 (Core Profile). - Current development focus:
- Performance improvement
MG_StateandMG_ImplforOpenGL 4.2 (Core Profile)Direct (Vulkan)backendDirect (OpenGL ES)backend
Build Instructions
We currently provide no releases and no precompiled binaries.
If you want to try the project right now, you’ll need to build it yourself:
-
Clone the repository:
git clone https://github.com/MobileGL-Dev/MobileGL.git -
Initialize and update all submodules recursively:
git submodule update --init --recursive -
Follow glslang’s own documentation for its required initiation.
-
Configure and build the project with CMake:
cmake -B build cmake --build buildor do it in a modern way:
cmake -S . -B build -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ cmake --build buildAlternatively, you can use platform-specific build commands as needed.
Build For macOS
On macOS, MobileGL can be built as a dylib that exposes the normal OpenGL/CGL/NSOpenGL entry points and routes them to the DirectVulkan backend. This is useful for running applications such as Minecraft through their stock GLFW/LWJGL OpenGL path while MobileGL is injected before context creation.
Prerequisites:
- macOS with Clang and Ninja.
- Vulkan loader and MoltenVK installed. With Homebrew, the MoltenVK ICD is commonly located at
/opt/homebrew/etc/vulkan/icd.d/MoltenVK_icd.json.
Configure and build:
cmake -S . -B build-macos-magma \
-G Ninja \
-DCMAKE_BUILD_TYPE=Release \
-DMOBILEGL_BACKEND_TYPE=DirectVulkan \
-DMOBILEGL_BUILD_TEST=OFF \
-DMOBILEGL_BUILD_BENCHMARK=OFF
cmake --build build-macos-magma --target MobileGL -j8
The dylib will be generated at:
build-macos-magma/libMobileGL.dylib
To run Minecraft by MobileGL from a launcher like PrismLauncher, keep the stock LWJGL/GLFW natives and add a wrapper command to the instance settings:
env DYLD_INSERT_LIBRARIES=/absolute/path/to/MobileGL/build-macos-magma/libMobileGL.dylib MOBILEGL_BACKEND_TYPE=DirectVulkan VK_ICD_FILENAMES=/opt/homebrew/etc/vulkan/icd.d/MoltenVK_icd.json
Also make sure the JVM arguments include:
-XstartOnFirstThread
DYLD_INSERT_LIBRARIES must be active before GLFW creates its OpenGL context. After startup, the Minecraft F3 screen should report MobileGL and the Direct (Vulkan) backend if the injection worked.
Build Options
| Option | Description | Default |
|---|---|---|
MOBILEGL_BUILD_TEST |
Build MobileGL tests (requires Clang) | ON |
MOBILEGL_BUILD_BENCHMARK |
Build MobileGL benchmarks (requires Clang) | ON |
MOBILEGL_FORCE_RELEASE_OPT |
Enable O3 and LTO in Debug build | ON |
MOBILEGL_ENABLE_TRACY |
Enable Tracy profiler for performance analysis | OFF |
Notes:
- The project requires C++23.
MG_TestandMG_Benchmarkcan only be built with Clang, not GCC. To enforce Clang, add-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++to your command.- On Android, tests and benchmarks are always disabled.
Environment Variables
MobileGL supports runtime configuration via environment variables.
Supported Keys
| Variable | Description | Allowed Values | Default |
|---|---|---|---|
MOBILEGL_BACKEND_TYPE |
Select active backend implementation at startup. | DirectGLES, DirectVulkan |
DirectGLES |
MOBILEGL_DISABLE_TIMERQUERY |
Disable GPU timer-query exposure and use. | 0, 1 |
0 |
MOBILEGL_USE_ANGLE |
Load ANGLE EGL/GLES libraries. | 0, 1 |
0 |
MOBILEGL_DISABLE_SUBGROUP |
Disable Vulkan shader subgroup support. | 0, 1 |
0 |
MOBILEGL_MAGMA_R11G11B10F_FALLBACK |
Use Magma's R11G11B10F format fallback. | 0, 1 |
0 |
MOBILEGL_MAGMA_FRAMESINFLIGHT |
Set Magma frames in flight. | Integer 1–64 |
3 |
MOBILEGL_AVOID_SAMPLER_MIPMAP_MIN_FILTER |
Avoid sampler mipmap minification filters. | 0, 1 |
0 |
MOBILEGL_COHERENT_AS_FLUSH |
Treat persistent GL_MAP_FLUSH_EXPLICIT_BIT maps as coherent (app-compat for engines like Flywheel that never flush them). |
0, 1 |
0 |
VK_ICD_FILENAMES |
Select the Vulkan ICD used by the Vulkan loader. | Path to an ICD JSON file | Loader default |
License
This project is distributed under GNU LGPL v3.0. See the LICENSE file in the repository for detailed information.