Skew perspective for a top-down view

Questions
,
1

I would like to skew the perspective like A link between worlds:
Top-down trick
But I would like to keep the geometry correct for shaders (shadows, light…). How to do it?

2

maybe add local y * 0.02 to transformed y, for example - using material.onBeforeCompile

3

I have never used onBeforeCompile. Can you give an example?

4

something like this.

5

Maybe its postprocess like glitch or underwater. Or you add custom postprocess shader
https://threejs.org/examples/webgl_postprocessing_glitch.html

6

sorry I have missed this part:

this is the opposite of what onBeforeCompile would do :sweat_smile:

then, you can limit the camera to show only the top part, where things get naturally skewed - for example like this