# Can't draw on or offset a Revolved surface perpendicular to axis

**URL:** <https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777>\
**Category:** Modeling Questions\
**Created:** [February 16, 2017, 2:49pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777 "2017-02-16T14:49:22Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![dclone2](https://avatars.discourse-cdn.com/v4/letter/d/71c47a/32.png) [@dclone2](https://discourse.shapr3d.com/u/dclone2)\
**Post date:** [February 16, 2017, 2:49pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777/1 "2017-02-16T14:49:22Z")

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Hi,

I subtracted a revolved object from another object, splitting it in half. Now, I’d like to create an offset (inset) of the inner face of said cut object, but it doesn’t not seem to be possible. Also when I try to draw sketch lines on the surface, they behave erratically. There is a line going from the edge of the face to its middle (where the revolve was on the object which was subtracted) and this, I assume, is the issue; revolved faces perpendicular to the axis seem to have unwanted properties, as they have a “seam” from the revolve. Is there an easy way to get around this?

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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:** [February 16, 2017, 3:33pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777/2 "2017-02-16T15:33:05Z")

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Can you post a screenshot? It is pretty hard for me to imagine / see what the actual issue is.

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<div class="post-metadata">

**Author:** ![dclone2](https://avatars.discourse-cdn.com/v4/letter/d/71c47a/32.png) [@dclone2](https://discourse.shapr3d.com/u/dclone2)\
**Post date:** [February 16, 2017, 3:44pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777/3 "2017-02-16T15:44:37Z")

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![](https://cdck-file-uploads-us1.s3.dualstack.us-west-2.amazonaws.com/flex002/uploads/shapr3d/original/1X/c3f2f3413d4c7a4795d790b2fc88f89636bf3b41.PNG)

The line through the shape also appears on my revolve. It’s transferred when I cut with the revolved shape

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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:** [February 17, 2017, 3:22pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777/4 "2017-02-17T15:22:15Z")

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I still don’t fully understand the problem. Sorry. ☹

Can you take a video of what happens?

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<div class="post-metadata">

**Author:** ![dclone2](https://avatars.discourse-cdn.com/v4/letter/d/71c47a/32.png) [@dclone2](https://discourse.shapr3d.com/u/dclone2)\
**Post date:** [February 17, 2017, 4:47pm UTC](https://discourse.shapr3d.com/t/cant-draw-on-or-offset-a-revolved-surface-perpendicular-to-axis/777/5 "2017-02-17T16:47:51Z")

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Recording a video off the ipad is not exactly the easiest thing to do. Suffice it to say, I found another way to do what I wanted here by another method.

Anyways, objects created by revolves aren’t great for subtraction or addition, as they inherit a “seam” from the revolve, and this isn’t easily removed. They pass this “seam” on to other objects (seen in the middle of the triangular piece above) if they are used to add or subtract from them. This seam essentially makes the face unstable; it can’t be sketched on or offset.

This is just disappointing as the revolve method I was using to cut the above piece was much faster than the alternative I figured out. I may post a video if I have time.