Investigate lack of transparency on certain mobile devices

[markschlosseratbentley]

Certain mobile devices do not succeed in rendering with full float transparency. On those devices, transparent geometry will fail to render.

Our typical workaround for these issues can be seen here.

However, we still sometimes get reports of other chipsets suffering from this problem and have to add them one-by-one to a detection list in iTwin.js. Furthermore, even with the workaround applied, the Samsung Galaxy Note 8 (Mali-G71) still shows potentially related problems in at least one dataset.

The afflicted devices include but are not limited to:

• non-M1 iOS/iPadOS devices with iOS/iPadOS >= 15 (when WebGL2 got supported).
• Devices with a Mali G-71 chipset (Samsung Galaxy Note 8, Android 9)
• Devices with a Mali G-72 chipset
• Devices with a Mali G-76 chipset (HUAWEI P30, Android 12)
• Possibly all Bifrost series GPUs (All the Mali GPUs above are Bifrost GPUs).

We should investigate this problem to understand why it happens and if we can fix it using some other approach than the workaround.

Of potentially related interest, the Mali G-71, G-72, and G-76 also have a workaround in place to disallow them from using MSAA because it can hang the devices.

[EimantasMorkunas]

To add - Samsung Galaxy S10e with Mali-G76 MP12 GPU did not have issues with full float transparency though did exhibit the hang with MSAA enabled. Huawei P30 has Mali-G76 MP10 but both devices report just Mali-G76 so there's no way to differentiate just by renderer. Might even come down to GPU driver version.