MTKView alpha low threshold

Hello,


When setting the alphaValue of an NSWindow, we can still see the window with very low alpha values (<0.05). That's expected.

However, with all proper alpha blending enabled, an MTKView is still visible with an alpha (out from fragment shader) of 0.045, but disappears suddenly somewhere between 0.044 and 0.045.

This is unexpected since even with 8bit alpha, the minimal step is far smaller (1/255=0,0039)

If alphaToCoverageEnabled is set to true, the alpha threshold to see the view vanishing is 0.5.


Is there any reason for that behaviour ? Can I improve it to use the full alpha range precision between 0 and 0.044 ?