# Line at Intersection of Two Planes

**URL:** <https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966>\
**Category:** Modeling Questions\
**Created:** [January 5, 2018, 12:51am UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966 "2018-01-05T00:51:59Z")\
**Posts on this page:** 12\
**Page:** 1

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 12:51am UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/1 "2018-01-05T00:51:59Z")

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I create a square in Top view. Then I set up a plane and rotate it 90 edges. If this were a room, the plane would be a wall. Say I want to make the wall an A frame. From the apex (in the plane) I want to draw two lines to the ends of the edge line used for the plane. Can’t seem to do this. Is it possible? If so, how? See Ss please.

![image](https://cdck-file-uploads-us1.s3.dualstack.us-west-2.amazonaws.com/flex002/uploads/shapr3d/original/2X/3/370f5b0beb7e6057d8099835bdd72a0f4f9b2cd3.jpg)

Thanks,  
Tommy

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 12:55am UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/2 "2018-01-05T00:55:31Z")

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To clarify further, I would expect the triangle to be a shape; turn blue when selected…

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**Author:** ![Gabor\_Shapr3D](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/gabor_shapr3d/32/235_2.png) [@Gabor\_Shapr3D](https://discourse.shapr3d.com/u/Gabor_Shapr3D)\
**Post date:** [January 5, 2018, 6:20am UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/3 "2018-01-05T06:20:33Z")

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You have to draw the 3rd side of the triangle as well. So not just the 2 sides going up, but the base as well. It will be overlapping with the square side, but that line is “on another” plane (cause you rotated it). If you do that, you’ll get a shape turning blue.

It is designed like this on purpose. Let’s say you

1. draw the square and
2. draw two lines up, so it becomes a triangle.
3. Later you delete the square.

Should that delete the 3rd line of the triangle or not? So that’s why you need to draw it again as it sits on another plane, even though visually they are overlapping.

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 4:00pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/4 "2018-01-05T16:00:40Z")

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Thanks for your prompt and clear explanation.

The question arose from my knife holder prioject — the surface of which is a number of intersecting planes at various angles. Started with base and was going to fold the other planes — one by one. But I may rethink this approach.

![image](https://cdck-file-uploads-us1.s3.dualstack.us-west-2.amazonaws.com/flex002/uploads/shapr3d/original/2X/f/f6ba516ea7d93f564368af4030dea070bdc37b1e.jpeg) ![image](https://cdck-file-uploads-us1.s3.dualstack.us-west-2.amazonaws.com/flex002/uploads/shapr3d/original/2X/5/5cbf7be3248e42bd3eb7b588f396c9500176a828.jpg)

Thanks again…

Tommy

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**Author:** ![Gabor\_Shapr3D](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/gabor_shapr3d/32/235_2.png) [@Gabor\_Shapr3D](https://discourse.shapr3d.com/u/Gabor_Shapr3D)\
**Post date:** [January 5, 2018, 5:18pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/5 "2018-01-05T17:18:31Z")

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I think you can perfectly recreate this model using construction planes.

I would:

1. Draw the first (bottom) plane
2. create a construction plane rotated over one edge
3. draw the the triangle
4. repeat 2 and 3 for the other side
5. create a new construction plane using (“Through 3 points”) for the sides
6. Draw the side sketches and you should be close to being ready

Double tapping on constructions planes will help you focus only on the side you need.

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 5:33pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/6 "2018-01-05T17:33:08Z")

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Gabor,  
Thanks for the advice. This is a good learning model…  
Tommy

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 7:43pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/7 "2018-01-05T19:43:49Z")

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I tried many times and ways to overdraw the base of the triangle but nothing worked. My solution was to draw a base line halfway down the triangle and then selecting its endpoints individually and dragging them to the vertex. Worked!

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<div class="post-metadata">

**Author:** ![Gabor\_Shapr3D](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/gabor_shapr3d/32/235_2.png) [@Gabor\_Shapr3D](https://discourse.shapr3d.com/u/Gabor_Shapr3D)\
**Post date:** [January 5, 2018, 8:00pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/8 "2018-01-05T20:00:31Z")

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This is how I would do it in version 1:

Works pretty ok.

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<div class="post-metadata">

**Author:** ![Gabor\_Shapr3D](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/gabor_shapr3d/32/235_2.png) [@Gabor\_Shapr3D](https://discourse.shapr3d.com/u/Gabor_Shapr3D)\
**Post date:** [January 5, 2018, 8:08pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/9 "2018-01-05T20:08:14Z")

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Or alternatively you can try this in version 2:

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**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 9:43pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/10 "2018-01-05T21:43:47Z")

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Thank you for the two approaches in the videos. I had difficulty completing the line with a plane 90 deg to the Top view. You might try this to see if possible?  
Thanks,  
Tom

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<div class="post-metadata">

**Author:** ![Gabor\_Shapr3D](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/gabor_shapr3d/32/235_2.png) [@Gabor\_Shapr3D](https://discourse.shapr3d.com/u/Gabor_Shapr3D)\
**Post date:** [January 5, 2018, 10:42pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/11 "2018-01-05T22:42:05Z")

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Works perfectly for me. Did it just like in the v1 video above.

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<div class="post-metadata">

**Author:** ![tommyn](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/tommyn/32/1714_2.png) [@tommyn](https://discourse.shapr3d.com/u/tommyn)\
**Post date:** [January 5, 2018, 10:52pm UTC](https://discourse.shapr3d.com/t/line-at-intersection-of-two-planes/1966/12 "2018-01-05T22:52:58Z")

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OK Thanks. Will try harder…