Issue with texture with transparency when using open gl es2.0 (google angle) on macos

[ypujante]

@mmozeiko

It really should be a question of disabling sRGB framebuffer setting for GLES when glfw window is created. Or other way around - enabling sRGB for desktop GL.

I know. I have been struggling to do just that for well over a week

[ypujante]

@mmozeiko

My guess would be that it with such setting it chooses OpenGL or software-rendered backend instead of Metal. You can use glGetString with GL_VENDOR / GL_RENDERER to check what you get.

I definitely get different results:

// with hint (correct result but slow)
INFO:     > Vendor:   Google Inc. (Apple)
INFO:     > Renderer: ANGLE (Apple, ANGLE Metal Renderer: Apple M2 Max, Version 13.4 (Build 22F2073))
INFO:     > Version:  OpenGL ES 3.0.0 (ANGLE 2.1.20982 git hash: f3e3810b917c)
INFO:     > GLSL:     OpenGL ES GLSL ES 3.00 (ANGLE 2.1.20982 git hash: f3e3810b917c)

// without hint (wrong result but crazy fast)
INFO:     > Vendor:   Google Inc. (Apple)
INFO:     > Renderer: ANGLE (Apple, Apple M2 Max, OpenGL 4.1 Metal - 83.1)
INFO:     > Version:  OpenGL ES 3.0.0 (ANGLE 2.1.20982 git hash: f3e3810b917c)
INFO:     > GLSL:     OpenGL ES GLSL ES 3.00 (ANGLE 2.1.20982 git hash: f3e3810b917c)

I also noticed while stepping through the code that without the hint, the glfw internal function chooseEGLConfig gets only 1 buffer config to choose from. With the hint it gets 10 and picks one…

After more research, it is definitely not a CPU/GPU issue. Using the hint, seems to limit the framerate no matter whether I call glfwSwapInterval(0) or not. So it is “slower” in the sense that it slowly drifts down to 60fps, but neither CPU nor the GPU are doing much.

I probably now need to investigate the Google Angle code to figure out why is there such a restriction

[ws909]

Is the framerate issues because of V-sync or similar? I don’t know anything about these tools that you use, but if when enabling the Metal backend, it might choose a different image presentation mode than for OpenGL; the issue might simply be that when presenting or acquiring a new swap chain image (or the Metal equivalent), the CPU waits on the GPU, and the GPU is limited in its selected mode to a certain framerate.

[ypujante]

Calling glfwSwapInterval(0) disables V-Sync and I did check that Angle makes the proper call into Metal to disable V-Sync which I detailed in this Angle Forum post.