v811_spc009/external/swiftshader/docs/ANGLE.md

ANGLE

About

ANGLE is a driver implementation that translates OpenGL ES to native 3D backends depending on the target system. Such backends include D3D on Windows, OpenGL Desktop, and Vulkan.

While SwiftShader initially offered a GLES frontend, this has been deprecated and replaced by a Vulkan frontend. In order to use SwiftShader for GLES, we now recommend using ANGLE on top of SwiftShader Vulkan.

Why use ANGLE instead of SwiftShader's GLES frontend?

There are a few reasons why SwiftShader's GLES frontend has been deprecated, and that we now recommend using ANGLE:

1. GLES 3.1 support - ANGLE supports GLES 3.1, while SwiftShader supports 3.0.

2. ANGLE's GLES 3.1 implementation, along with SwiftShader's Vulkan 1.1 implementation, are both Khronos-certified conformant.

3. ANGLE's GLES validation is more complete than SwiftShader's.

4. Dropping support SwiftShader's GLES frontend allows our team to focus our efforts on implementing a solid and conformant Vulkan frontend instead.

How to use ANGLE with SwiftShader's Vulkan frontend

In order to build ANGLE, you will need to install depot_tools. You will also need Python 2 installed. Note that ANGLE does not offer a CMake build at this time. Follow the official dev setup to install all required tools, clone ANGLE and its dependencies, and build it. This will look something like:

cd angle
gn gen out/Release
autoninja -C out/Release

This will build all ANGLE targets into the out/Release directory, including:

• libEGL.so
• libGLESv2.so
• libvk_swiftshader.so

As long as your application uses ANGLE's libEGL and libGLESv2, ANGLE will take care of translating to a default 3D renderer for the current platform.

There are multiple ways to have ANGLE use SwiftShader Vulkan as its backend:

1. Set ANGLE_DEFAULT_PLATFORM=swiftshader environment variable. When running your GLES application, ANGLE will use libvk_swiftshader as its Vulkan driver.

2. Set both ANGLE_DEFAULT_PLATFORM=vulkan and VK_ICD_FILENAMES=path/to/angle/out/Debug/libvk_swiftshader_icd.json environment variables. When running your GLES application, ANGLE will use it's Vulkan backend, and the Vulkan Loader will load libvk_swiftshader via the Vulkan Loader.

3. Using the EGL_ANGLE_platform_angle extension. As described in this section of ANGLE's setup documentation, you can use the EGL_ANGLE_platform_angle extension to select the renderer to use at EGL initialization time. Use the ANGLE_platform_angle_device_type_swiftshader device type to select SwiftShader specifically (see documentation here).