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PS1 Vertex Distortion / Quantization Material?

How can I make my models or model materials have that weird distortion that old PlayStation 1 games had with the vertex distortion/shaky-ness or what some would call it quantization? I have seen the marketplace item called Oldskooler but I don't have the money for it and don't want the other effects that come with it (also, I'm not sure if it will work well with my game graphics, I just want to experiment with the graphics, maybe I won't like it and remove it), I just want the distortion effect. Also, there is a PC game that got that weird effect too, Unreal Tournament GOTY 1999 had it too with the character models, but not quite like PS1 games.

Here's an example comparison of a PS1 game with and without distortion due to lack of z-buffer:

https://www.youtube.com/watch?v=yOASkImiNeU

Product Version: UE 4.19
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asked Jul 17 '18 at 03:23 PM in Rendering

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Oblivion2500
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avatar image tapirtoon Jan 23 '19 at 08:28 PM

someone actually made a post process material for this. Here you go: https://www.youtube.com/watch?v=V53WhPBXpW0

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The reason it was called quantization is because that is literally what was happening. Vertex positions were being passed to the rasterization hardware as integers instead of as floating points so the coordinates would "snap" into place. It also quantized based on screen resolution. You can do the same thing with a vertex shader but simply rounding your vertex positions to the nearest "pixel." Of course, we can control what this made up screen resolution is so you can simulate an old 320x240 screen even if your real resolution is 1920x1080.

I don't know what your familiarity is with creating materials but you can use the world position offset to adjust the vertex position. The pseudocode of what you want to do is

  1. Get post-projection vertex position

  2. Divide by vertex.w component to remove projection warping

  3. Round x and y of vertex to nearest "virtual pixel" (floor(vertex * dim) / dim)

  4. Multiply by the vertex w component to reapply warping

  5. Get difference between quantized and non-quantized vertex and set it to world position offset in material

Hopefully that makes sense. I don't know if that is enough to get you where you want to be.

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answered Jul 17 '18 at 07:05 PM

Brian Johnstone (suspended)
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