# Rotate a line or object until it strikes another line or object

How do I rotate a line (or an object) to touch a surface or another line?

I have not been able to find a way of doing the rotation in a manner that ends up with the end point of the line touching the surface or line (without otherwise extending the line).

I can rotate and get close, but there is no obvious inference for connecting the end point to the line or the surface.

I would use the Free Rotation tool in FredoScale for that. He designed the tool to do exactly what you want.

You could also use the Arc tool (not 2-point Arc) to draw an arc from the center of rotation and the end of the rotating element to find the point at the destination. Then use the native Rotate tool.

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Thanks dave.

The free rotation didnâ€™t seem to achieve the goal.

The Fredo Scale Box Rotation tool did achieve the result of rotating to and touching the line or surface, but I had to zoom right in to the contact point and look for a very fleeting inference pop-up. It was extremely difficult to pick.It felt very â€śhit and missâ€ť.

I was reluctant to use an arc because it is made of straights meaning the arcâ€™s intersection point will minutely different to the true contact point for a rotating radial line, and that minute difference means the radial line wonâ€™t connect.

It sounds like you werenâ€™t using the Free Rotation tool correctly, then. Iâ€™d make an example to show but Iâ€™m on my phone. Some years ago I did a tutorial showing it, though. Iâ€™ll try to find it.

As for the Arc tool, it doesnâ€™t matter that the arc is made of straight line segments. Itâ€™s the endpoints of the arc that are of interest in this case. First end of the arc on the end of the rotating element, the other end on the destination. If you pay attention while drawing that arc, youâ€™ll also know the angle of rotation required.

Those instructions helped a lot, and I can see the free rotation tool helping me as lot in the future. I have previously struggled with fitting of braces and other parallel sided objects into an existing fixed geometry.

My situation is a little different in that the member/object is fixed in dimension, and I just need to swing it around an axis until it contacts an adjacent surface or line. Sometimes I can achieve that using the Fredo Box Rotate tool, but the inference is pretty touchy and frustrating.

I tried your suggestion of an arc, but I could find an arc tool (centre and 2 points) whose 2 point would extent the arc out to exactly reach out to the edge or surface and display a clear inference such as â€śon edgeâ€ť or â€śon surfaceâ€ť.

I feel like I keep pitching 'em and you keep missing 'em.

Although I showed adjusting the length of the diagonal after rotating, you can rotate the entity so its end meets at the destination as you want to do. You just need to watch the inferencing indications.

As for the Arc tool, do as I described before. Cclick to set the center of rotation. Then click at the end of the entity you are rotating and drag out an arc that ends at the destination for the rotation. The arc can be drawn so it shows the exact point where your rotated element should land.

Sorry to be so frustrating!

I know what you are saying, but I am looking very closely for the appropriate inferences to show up.

I am using the simplest of test models, just a rectangle and a line, and rotating the line to hit the face or an edge of the rectangle.

As I slowly and carefully rotate the line (using the end point of the line) there is initially no inference other than when I am hanging on to the end of the line with the cursor at which time the inference is saying â€śend pointâ€ť. That inference flickers on and off because of my jerky mouse movements despite best intentions.

When trying to touch the line to the edge of the rectangle, after numerous attempts, I did have success a couple of times when the inference changed to â€śend point on lineâ€ť and it had actually connected at the same location.

I didnâ€™t have any success connecting the line to the surface. The best I could achieve was to change the inference to â€śintersectionâ€ť, but by that time the line had passed through the surface and rotated/gone too far.

I did have marginally better success rate with the box rotate tool, but had to be extremely careful and deliberate.

I had another look at the arc. When I drag out an arc it does not recognise any intersection with a surface. It will intersection with a line drawn on the surface.

It looks like precision rotating based on intersecting other entities in a model is not a sketchup strongpoint. Perhaps the geometric number-crunching behind the scenes is to demanding. Calculation of geometry of curves is not an easy task.

First time youâ€™ve mentioned trying to infer to a face.

When I get home from work, Iâ€™ll make an example.

I had a look too. It seems that an inference can be found with the arc tool, at least with the very simple test groups used below. I donâ€™t know why the intersection only shows well away from the cursor. I think it should work better than this.

Shep

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