psx-retro-rendering

Implement the effect in layers: set a 320x240 viewport, cancel perspective-correct UV interpolation by multiplying UVs by clip w at the vertex, snap vertices to screen pixels after projection, then apply the PS1 dither matrix and RGB5 quantization in the fragment shader.

Multiply UVs by the clip-space w component in the vertex shader, let the GPU interpolate, then divide by w in the fragment shader. Subdivide large meshes to control the resulting affine distortion.

A low-resolution filter alone misses the defining traits: affine texture mapping, integer screen-coordinate vertex snapping, RGB5 color depth, and per-polygon conditional dithering. Each must be implemented as a separate shader layer.

Yes, by quantizing clip-space coordinates against the viewport size in the vertex shader after projection. Snap to the actual render viewport resolution, not an arbitrary world-space grid, to reproduce authentic wobble.

Godot's screen-texture approach moves materials into the transparent pass, so overlapping transparent objects cannot blend with each other reliably. The four fixed PS1 blend equations work against the framebuffer but not between transparent meshes in the same pass.

Avoid it for ordinary low-resolution or pixel-art presentations that do not need PS1-specific behavior like affine warping or hardware dithering. It is also unsuitable when exact polygon draw ordering is required, since flat depth is only an approximation.