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.
Desktop 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
Note that this guide is mostly Windows oriented. For other desktop platforms, please adapt accordingly!
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!
You need GPU which supports OpenGL ES context or ANGLE. As previously written, todays desktop GPU should support this, thus ANGLE is normally unnecessary.
Tell LOVE to use OpenGL ES context
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.
lovec .... 0.10.2 or later is assumed.
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 one of these application:
- 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
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).