Seeking explanation for odd UV projection artifact

This is the artifact im talking about, there is a solid chance you already know exactly what im after, but just in case, let me elaborate.

Here is the texture, and the UVs, so its very obvious what result im expecting.

If i subdivide the plane, the grid will curve itself

And this is what the subdivided 2D grid looks like. Pay attention to the two i’ve marked

If i do project from view again, i get a result that i’d expect

And the new UV map looks like this.


Question time
This is, again, how the grid looks if i unwrap, THEN subdivide

This is how the grid looks, if i subdivide, THEN unwrap.

Why is the distortion seemingly inverted along the x axses? Is there any way to combat this, so i get proper results without dividing the plane alot of times? Im after a solution, but also a technical explanation so i can understand whats actually going on, fundamentally.

For info, im still on blender 2.79. No im not a boomer, its just been a very long time since i’ve used blender, and this project is for something important, with a deadline, so i have to use what im familiar with.

Same happens in 2.8 btw, notice how the UV map is “inverted” along the X axses if i re-unwrap project from view.

If you want to test this in the current version, here is a gif to show the setup process if its not already obvious:

This is going to be the same no matter what version you use. When you unwrap first, then subdivide, it also subdivides the UVs evenly (in 2d space). if you look at the first of the comparison images, you’ll see that the polygons, while shorter, are equally as far apart (can compare with the grid lines).

In the second you’re using the viewport window view of the mesh as the UV layout AFTER you’ve subdivided it, and that “distorts” (due to perspective) the UV coords.

this is normal behavior.

The lines curve on your first example b/c you’ve done “project from view” and the perspective is “pinching” it

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