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I'm trying to unwrap a few faces of my model at 1:1 scale to fit onto an image that I've prepared to be 1:1 scale as well. Everything I've tried has resulted in a distorted unwrap one way or another. The closest result I've found is to unwrap with Cube Projection - that seems to keep the relative locations of the face correct, but the X and Y scale needs to be manually tweaked. The desired result will have the X and Y scale at 100% of the original (or at least X and Y will be the same), and the relative positions of the faces need to be the same as the original.

In the image below, the Y scale has worked OK, but the X scale is compressed.

I tried the "World Scale UV" tool of the 'Magic UV' add-on (suggested in a similar question), but I couldn't get a useful result from that.

All transforms and scales have been applied. I don't know if it's relevant, but the original geometry has been created via geometry nodes and modifiers that have since been applied.

enter image description here

I've attached the blend file from the image above for reference.

EDIT:It just occurred to me that my model isn't directly on the XZ or YZ plane, so the UV wrap could just be a projection of the faces to one of those planes - is that the case?

CLARIFICATION: When I say 1:1 scale, I mean that the image is the correct dimensions for the intended geometry. i.e. the height and width of the image matches the height and width of the geometry. I'm NOT referring to an aspect ratio of 1:1 which seem to be the understanding.

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  • $\begingroup$ By default, the UVs are represented in a UV canvas that is 1:1 (square) if you use a image that is not 1:11 like 1:2 ( example size: 512X1024) the UVs are going to mapp itself into that new aspec ratio, so the same UV's are going to look shorter or thinner depending on the aspect ratio of the image. the recommendation is to always use a 1:1 aspect ration like 1080X1080 2048 X2048 and so.... for your images to avoid this visual distortion in the UV editor. $\endgroup$
    – Emir
    Commented Nov 17, 2022 at 14:09
  • $\begingroup$ Ok, so I want my model faces projected on to my image without any mapping out distortion. E.g. a model faces that is 1000px wide by 2000px tall appears in the UV editor the same dimensions. Will adding black space either side of my image to make it square help? (I'm on my phone, will test it later) $\endgroup$
    – G.H.
    Commented Nov 17, 2022 at 21:30
  • $\begingroup$ Folowing up on the suggestion of using a texture image with 1:1 aspect ratio - this did solve the problem of UV faces being distorted in the X direction (i.e. my X and Y dimensions were proportionally correct), but it didn't help with the overall scale (i.e. my UV faces were still much smaller than the image - which was sized to match real life (e.g. 1:1 scale not 1:1 aspect ratio). I can't find anything to suggest that the UV faces can be sized 1:1 (1 model unit = 1 UV unit). $\endgroup$
    – G.H.
    Commented Nov 21, 2022 at 11:11

2 Answers 2

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Technically, your UVs seem correctly unwrapped. The issue is the texture you are using isn't 1:1, it is narrower on the X axis. The UVs occupy all the texture space from 0:0 to 1:1 no matter the texture.

texture space

The simplest solution would be to edit your texture image so that it is a perfect square. Let your texture info on one side, and use the remaining space for a different texture, it's actually better in render speed this way.

optimization

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  • $\begingroup$ What do you mean by my texture being narrower on the Y axis? The texture was created from dimensions taken from Blender. In any case, if you refer to the image in my original post, the X axis is clearly narrower on the UV than in the model (as shown by red arrows). $\endgroup$
    – G.H.
    Commented Nov 17, 2022 at 4:21
  • $\begingroup$ Erratum, narrower on the X axis. The UV space is to be considered as a grid that defines how your mesh is unwrapped on it from left to right and from top to bottom. When your texture isn't square, it will still read from left to right and from top to bottom, except now your texture is narrower on one axis, so the UV follows that. That is why you should use square textures all the time when mapping with UVs. $\endgroup$
    – Lauloque ♦
    Commented Nov 17, 2022 at 17:18
  • $\begingroup$ If you look at the first screenshot, you can see the difference between your texture size and a square texture size. The UVs are the same, only the texture is different. $\endgroup$
    – Lauloque ♦
    Commented Nov 17, 2022 at 17:19
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As Lolock says, your image is not square (1:1 aspect ratio), by default it will squeeze the UV when you'll unwrap it. To avoid that, either use Lolock's solution or keep the Image Texture node selected when you unwrap, it will keep your UV at its good proportions.

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  • $\begingroup$ Hi, I don't understand what you mean when you say my texture isn't 1:1... perhaps we have a different definition? When I say 1:1 I mean the scale of the image texture exactly matches the real scale in real life. NOT the aspect ratio (It sounds like that's what you're implying?) $\endgroup$
    – G.H.
    Commented Nov 17, 2022 at 11:34
  • $\begingroup$ Yes I mean the aspect ratio $\endgroup$
    – moonboots
    Commented Nov 17, 2022 at 11:40
  • $\begingroup$ Thanks for the help, but that's not what this problem is about. $\endgroup$
    – G.H.
    Commented Nov 17, 2022 at 12:27
  • $\begingroup$ I was trying to address this problem: "the X scale is compressed". If you select the Image Texture when unwrapping, the X should not be compressed. Is it not your problem? $\endgroup$
    – moonboots
    Commented Nov 17, 2022 at 13:14

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