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I have 3 equilateral triangles.

The red triangle is the base and then at 90 degrees I have two green other triangles.

View 1 and 2 shows this setup from two different angles.

enter image description here

Below I have a kite like shape that I have marked as (P) that I want to place against the two green triangles.

enter image description here

As you can see in image 4 ... I'm having a really hard time getting the 3 vertex's on shape P to be places exactly on the vertex's for the two green triangles.

Everything I try either changes the shape of the object .. or as I move one vertex I change the position of another vertex that I have already placed correctly.

Here's a link the file itself: enter link description here

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  • $\begingroup$ In which position do you start with the "P" face, maybe flat on the xy plane? $\endgroup$
    – Xylvier
    Mar 27, 2020 at 1:13
  • $\begingroup$ Yes, flat on the x,y $\endgroup$ Mar 27, 2020 at 2:05
  • $\begingroup$ May i ask if the "P" face has certain measurements that need to be kept, as it may be easier to create the shape in place if for example the length from the lowest to the top were known. $\endgroup$
    – Xylvier
    Mar 27, 2020 at 2:09
  • $\begingroup$ Yes P has exact measurements that I used to create it while flat on the xy .. I probably could create it in place with some trouble but I want to keep the parts as I plan to animate the parts later on. More than anything it's just annoying me that I can't find a way to do it :) $\endgroup$ Mar 27, 2020 at 2:25
  • $\begingroup$ I ask as i had no measurements, so i had to create one in place and get that then flat on the xy plane XD .. right now working on a way to get it then back in place .. XD $\endgroup$
    – Xylvier
    Mar 27, 2020 at 2:28

2 Answers 2

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Based on the comments i build the setup myself, created the "P" face as it was called in place, took it down flat according to comments again and then started working it back in place.

Here a visual step by step: enter image description here

It's based on the following:

  1. Begin by creating a support triangle.
  2. For that use K knife tool and hold Ctrl to snap on the middle of the base triangle edge that lies opposite of the tip where the "P" face has to go.
  3. Select the top 2 vertices from each of the "green" standing triangles and press F to generate an edge between them.
  4. Select the edge and press Ctrl+R to cut the edge in half, confirm with Enter
  5. Now create a triangle from the new created vertex and the 2 vertices along the cut you made through the triangle. This will help aligning the "P" face.
  6. Now go to the "P" face and in edit mode, then press Shift+S to snap the cursor to the selected vertex on the thin "P" face tip.
  7. Go in object mode and set the origin to the cursor using the context-menu.
  8. Switch to the other object and select the vertex where the thin tip of the "P" face has to go, snap the cursor there.
  9. Back to the "P" face object use Shift+S "snap selected to cursor"
  10. The "P" face object is now at least with the tip at the right location.
  11. Adjust the settings for the snapping like so:
    enter image description here
  12. Now it's important that all vertices of the "P" face object are selected, BUT the last selected(active) vertex has to be the one at the tip opposite the thin tip where the origin is. enter image description here
  13. Press R, followed by Z, locking the rotation to Z axis and then hold Ctrl to snap based on the active vertex onto the vertex the support triangle, where it divides the base triangle edge.
  14. Now back to the base object, in edit mode select one of the 2 edges of the divided edge on the base triangle opposite to the thin tip of the "P" face.
  15. With the edge selected create a custom orientation like this:
    enter image description here
    It will create and select a custom orientation we need to rotate the "P" face.
  16. Back to the "P" face object, select again all vertices of and make sure the last/active vertex is the one like we used last. Opposite the thin side.
  17. Now press R, followed by Y (is the axis of the custom orientation we need), then hold Ctrl and snap based on the active vertex onto the top vertex of the support triangle.
  18. All that is now needed is cleaning up the support triangle.
  19. If you have multiple "P" faces that need to be placed, you can create a duplicate it and after removing the custom orientation snap each copy to the 2 other corners of the base object, after which you only need to rotate them with R, followed by Z with 120 degree either plus or minus.

With one extra "P" face it should then look like this:
enter image description here

I have looked at the file, and i had to notice that the "P" faces were slightly too long...



Little extra, as i was already mostly done with the answer:
To round it up i think it might help showing you how i build the version i used:

  1. Add a circle mesh with 3 vertices, radius 1
  2. Select an edge and create a custom orientation from it.
  3. Snap the cursor to the edge
  4. Select the vertex opposite the edge, copy it with Shift+D, cancel with RMB to leave it where it was.
  5. Press R, then Y followed by -90 to position the vertex where it needs to be to form a new triangle you can now build by selecting the new vertex and the two on each side of the edge in between which the cursor is.
  6. Do the same on the other side and you have the 2 "green" triangles standing.
  7. Now select the 2 vertices each top of the "green" vertices and press F to create an edge between them.
  8. Cut the edge with Ctrl+R, confirmed with LMB.
  9. Select that new vertex and the vertex in the corner where the "P" face thin side will be and press F, creating an edge we can use to find the opposite tip of the "P" face.
  10. Looking from top, select the vertex between the tips of the 2 "green" triangles and press G twice to start sliding the vertex along the long edge downwards.
  11. While in this slide mode, press C to disable the clamping.
  12. Now move along the long edge and over the cross-section towards the center of the base triangle. We can sadly not snap in this mode yet, but you will find that the closer to 0 on x and y you come the more you come closer to 2 on Z.
  13. That said, with the values used the exact position would be 0,0,2.
  14. Now with the vertex in place, you can create a face on each side and then dissolve the edge in the middle.

Based on what values you used i believe it should have come to fit, but since the version in the file was overlapping, either moving the vertices caused that or some measurements could have been slightly off.

Happy Blending.

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  • $\begingroup$ wow, I'm learning SO MUCH from your answer. Thank you ... I'm rather new to Blender and don't want to ask 100 stupid questions as I walk though this. Incredible response, thank you so much. Plan to go through this in detail this evening. Currently having a problem at step 13 for some reason it's just not snapping the way your is so I'm doing something silly. Will keep you posted, thanks again. $\endgroup$ Mar 27, 2020 at 14:54
  • $\begingroup$ I added the picture from the gif that shows the step before 13, as it is very important and might be a bit harder to understand from the text version then the picture. $\endgroup$
    – Xylvier
    Mar 27, 2020 at 19:54
  • $\begingroup$ This was hands down the best response I've ever received, thank you again so much. I really learnt a lot from this. To start with I realized that I didn't understand how the snapping works.. then the custom orientations .. had no idea those exists. Excellent stuff, thank you sir! $\endgroup$ Mar 29, 2020 at 16:58
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You can try snapping to vertex or edge.

enter image description here

enter image description here

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  • $\begingroup$ no unfortunately this doesn't seem to have the effect I'm looking for. $\endgroup$ Mar 27, 2020 at 2:26

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