Simple undivided plane UV map not behaving as expected

Question

I’m running into a UV map error (or at least it’s not behaving as I expected it would). I have a simple plane with 4 points and I’ve set up the uv to a sqaure texture (images below). I would expect the texture to be applied evenly, following the trapezoid shape of the plane, and instead it’s sort of bending along the middle. I’ve tried applying visual and object transforms, but that hasn’t changed anything. I've also tried subdividing and triangulating the faces, only for it to continue to bend the texture in a way I wouldn't expect.

Does anyone know if this is how it’s supposed to be behaving or maybe I have a setting wrong? Thanks!

^ UV map for the plane, snapped to pixels

^ how the plane is appearing

Answer 1

A face is always composed of 2 triangles, the oblique goes in a sense or in the other:

so if you give your face an image texture then deform the face by moving its vertices, the result may be unexpected deformations like this:

You have several solutions like creating directly the final quad shape instead of deforming a square face, or subdivide enough your square so that the deformation becomes not noticeable.