Affine texture mapping
Texture interpolation that ignores depth — cheap, but it makes textures visibly warp and swim, the signature look of the PlayStation 1.
The method interpolates texture coordinates linearly across a triangle in screen space, without dividing by depth the way perspective-correct mapping divides by w. That saves a division per pixel, but on triangles tilted away from the camera the texture skews and wobbles as you move. The PS1 (1994) had neither hardware for perspective correction nor a depth buffer, so its games are full of this shimmer, while the N64 and PC 3D cards did perspective-correct mapping and looked "right."
Developers hid the artefact by subdividing large polygons into smaller ones, where the error per triangle shrank. Today it is deliberately revived as a PS1 aesthetic in indie horror.