Displace a 3d point by a fixed pixel offset in screen space?

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:bust_in_silhouette: Asked By Kelvin

How do you displace a 3d point by a fixed pixel offset in screen space?

In GLSL you could do for example

vec4 clip_space   = projection * view * model * position3d
// manual perspective division
vec2 screen_space = clip_space.xy / clip_space.w 
// perform displacement in screen space, in units of pixels
vec2 displaced    = (screen_space * viewport_resolution + pixel_displacement) / viewport_resolution
// set z to 0 and w to 1 to disable hardware perspective divide
glPosition = vec4(displaced.xy, 0, 1)

but the godot shader system doesn’t seem to let you modify the perspective and projection order like this.