GLES Shader Testing in Desktop

Writing shaders to support mobile devices might be not trivial. You may wondering is there a way to test shader in mobile devices without really using mobile device.

The answer is yes, there's a way.

GPU nowadays (even integrated one) should supports creating OpenGL ES context, which means all shaders must be GLSL ES/ESSL compatible. We can make LOVE to use OpenGL ES context by using environment variable LOVE_GRAPHICS_USE_OPENGLES=1.

Note that this guide is mostly Windows oriented. For other desktop platforms, please adapt accordingly!

love.graphics.validateShader

Since 11.0, there's love.graphics.validateShader which can be used to validate both GLSL and ESSL shader code. Note that it only validates, it doesn't run your shader code. If you really want to run your game under GLES context, proceed below!

Requirements

You need GPU which supports OpenGL ES context or ANGLE. As previously written, todays GPU should support this, thus ANGLE is normally unnecessary.

Tell LOVE to use OpenGL ES context

FIXME: AMD drivers expose OpenGL ES context under EGL (and it's very hidden) which is not compatible with LOVE SDL build. For AMD GPUs in Windows, proceed below on using ANGLE directly.

Now, we need to tell LOVE to use OpenGL ES context. You need to set this environment variable before starting LOVE. It can be set using Command Prompt/Terminal and launching LOVE from same Terminal, or from Windows, from Advanced System Settings.

• Windows: set LOVE_GRAPHICS_USE_OPENGLES=1 then lovec .... 0.10.2 or later is assumed.

• Linux/macOS: LOVE_GRAPHICS_USE_OPENGLES=1 love ...

Verify if LOVE uses OpenGL ES context by checking the 1st return value of love.graphics.getRendererInfo which should be "OpenGL ES".

Once you got OpenGL ES context, you can test your shader code if it works under mobile devices. Otherwise, if you're on Windows, proceed below.

Using ANGLE in Windows

ANGLE is an implementation of OpenGL ES 2.0 and 3.0 on top of other rendering backends. In Windows, it will run OpenGL ES using Direct3D 11 or Direct3D 9. If your GPU doesn't support OpenGL ES context or if you want to force ANGLE, you can copy libEGL.dll and libGLESv2.dll from here, or on one of these applications:

• Google Chrome

• Microsoft Edge Chromium

• Visual Studio Code

• osu! stable (32-bit DLL)

Note: Using Firefox's DLLs doesn't work because it links with Firefox-specific DLLs and copying all the dependent DLLs can be troublesome.

One thing for sure is make sure the bitness of the DLL matches, i.e. 64-bit Chrome has 64-bit DLLs and can only be used on 64-bit LOVE.

Next, set the environment LOVE_GRAPHICS_USE_OPENGLES=1 and SDL_OPENGL_ES_DRIVER=1 then launch LOVE. To confirm you're using ANGLE backend, check the 2nd return value of love.graphics.getRendererInfo which should contain "ANGLE" (all uppercase).