writing to `POSITION` gives wrong `VIEW` in fragment shader

[darthLeviN]

Tested versions

stable 4.3

System information

Kubuntu 22.04

Issue description

If you write to POSITION to make a full screen post processor, then your VIEW vector will become invalid and you have to calculate it manually. What i observe that if i write to POSITION then the VIEW variable will become affected by camera translation.

Steps to reproduce

write to POSITION

Minimal reproduction project (MRP)

viewbugreport.zip

[tetrapod00]

Possible docs fixes:

• Add a note about this in the Advanced Postprocessing page, where the docs recommends setting POSITION manually.
• Elaborate on the limitations of POSITION in the Spatial shader builtin table.

[darthLeviN]

Possible docs fixes:

• Add a note about this in the Advanced Postprocessing page, where the docs recommends setting POSITION manually.
• Elaborate on the limitations of POSITION in the Spatial shader builtin table.

so this is a limitation not a bug? is the wrong value of VIEW used for something else?

[tetrapod00]

Likely a limitation and not a bug. I'm not sure since I haven't looked at the source just yet. From the Advanced Postprocessing page:

POSITION bypasses the built-in transformations and sets the vertex position in clip space directly.

From that, I would expect that setting POSITION in vertex() probably would not affect the automatically calculated VERTEX or VIEW in fragment(),