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I have two models, for simplicity let's say an Octahedron and an Icosahedron, and I'd like to move the Octahedron so that a particular one of its faces aligns with a particular face of the Icosahedron, so that I can then join them into one model.

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I am fine with translating, rotating or scaling either model, I just don't want to distort them.

Once I've got them aligned, joining the faces is the easy bit. I can also do the scaling pretty easily since I just measure two edges find the correct ratio and scale one model by that value. I can do all that, but I don't know how to move them so they perfectly align. Trying to do so manually they are still misaligned after tweaking things. I would like to do this operation more than 50 times in total, and even though I will likely get better with time, it just doesn't seem like a viable method.

Misaligned models

This question is very similar but it's constrained to simply sliding parallel faces the right distance along an axis. My faces are not parallel and need a more complex set of transforms to align them.

In short I'd like some way to take two congruent or similar faces and translate one of the models so that the two faces are incident. Is there a good way to do this?

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  • $\begingroup$ Do you need the faces to be scaled to one another, too, or just centered? $\endgroup$
    – Robin Betts
    Dec 31, 2022 at 17:17
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    $\begingroup$ @RobinBetts I can measure the lengths of the edges and calculate the scaling factor myself, so in principle I don't need it, although it would save some time if I could do it all in one. $\endgroup$ Dec 31, 2022 at 17:20
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    $\begingroup$ It's a paid solution so I'm not posting it as an answer, but I'd recommend the "3 Points Align" addon: blendermarket.com/products/3-points-align You just choose three points on two objects and it aligns them, with an option to scale ("Match Distances"). There's also the free MeshAlignPlus addon: github.com/egtwobits/mesh_mesh_align_plus/releases which works, but much harder to use. $\endgroup$
    – Kuboå
    Jan 1, 2023 at 21:14

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Let's say you have these 2 objects with their target faces marked in blue. These are the faces to which the objects should snap & align. You can enable Face Project type of Snapping with the following settings shown below. Make sure Transform Options is set to Affect Only Origins.

enter image description here

Select an object, say the Octahedron, and press G to move its Origin and then hold down Ctrl while moving it to the target face. Notice how the Origin starts to snap and point into the Face Normal's direction. Then click LMB or press Enter to confirm. Press RXX180Enter to rotate the Origin 180 degrees along the local X axis. Again click LMB or press Enter to confirm. Now the Origin's local Z-axis is facing in the opposite direction relative to the target Face Normal.

enter image description here

Then untick Affect Only Origins in the Transform Options to return to normal object transform mode. Select the object and move it over the other object's target face and then press Ctrl to make it snap to that target face. Then click LMB or press Enter to confirm. Notice how the 2 blue surfaces perfectly align.

enter image description here

If you need the faces to perfectly align at their centers you can use the Cursor to Selected on the target face in Edit Mode and the Selection to Cursor in Object Mode using Shift+S on the Octahedron and then do a Shift+S > Cursor to Selected on the Icosahedron's Target face in Edit Mode. Then once you have snapped the Octahedron to the Icosahedron, you select the Octahedron and press Shift+S > Selection to Cursor so the center of the Octahedron's target face aligns to the center of the Icosahedron's target face. You can rotate the Octahedron on the local Z-axis to adjust rotation using RZZ.

enter image description here

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  • $\begingroup$ This does not work in Blender 3.6. A smile sphere snaps but when I have a complex object such as a wing with more surfaces it fails to snap. It is absolutely ridiculous that Blender can’t align the faces of two objects without a simple select the faces and align $\endgroup$
    – Carlos 500
    Oct 15, 2023 at 15:40
  • $\begingroup$ @Carlos500 i'm not sure what you mean by "smile sphere", but can you have a look at this thread and if that also does not resolve it, can you post a new question with detailed description of the problem and reference this thread so we can have a look :) and also add a blend file with a simple setup that reproduces your issue. $\endgroup$ Oct 15, 2023 at 22:53

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