Question concerning circles & quadrants
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I sure hope I'm not going to get on anyone's nerves with my questions. I promise I always try to find my answers in the Help menu, and even look at videos again (I've viewed all the tutorial videos), but when I can't find what I'm looking for, you guys are my only hope.
I'm trying to find the point in a circle that is the endpoint of a diameter line which would be parallel to all of the lines drawn in one direction in my drawing (the other lines being perpendicular to that imaginary diameter line). In AutoCAD, it's so easy to find -- one just clicks on the Quadrant button, but here in SU, the auto-find system wants to hook onto an endline of one of the segments of the circle, and in my case, none of them match up with that "quadrant" spot I'm looking for.
Also, I can't use the measuring tool to make a guideline, because the circle is the top of a spindle in my banister, and it's sort of floating in space, and not next to any line I can use from which to get a guideline.
I'm pretty sure there must be a simple way to find this spot on a circle, and I just don't know it yet. Anyone?
Thanks in advance,
Gigi
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I'm not positive I understand the question, but I think there are a couple of ways to do it. You could use the line tool and click on the center of the circle (hover over the edge of the circle first, then move towards the center and it should snap to the center). Once your on the center, click to start a line. Now hover the line tool over a line you want to draw parallel to (but don't hover over an end point or midpoint on the line or it won't know what to inference - just hover over a plan part of the line). Now move the cursor back and try to draw in the direction of parallel. It should snap to a pink inference line which is an inference based on other geometry - the line you have hovered over. Once you grab that inference, hold shift to lock in place. Then draw it out the edge of the circle and click to finally finish the line.
Or another way would be to just copy a line that you want to be parallel. Copy and place it on the center of the circle. If it hits the edge of the circle, then that is the point you want. If not, then just extend it by drawing a little more to the end of it.
Hope those make sense. I would normally do the first option, but sometimes inferencing other lines can be tricky if there are lots of lines around. Let me know if it works, or if it doesn't make sense.
Of course there's the huge possibility that I entirely misunderstood the question.....
Chris
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As the circles in SU are in reality polygons, no very sophisticated geometrical operations can be performed with them with reasonable accuracy.
As to the quadrant question, when I need those, I make the circle with a number of segments divisible by four, that's the most accurate I can get. Note that the vertices (endpoints) of the circle are the only parts of it that lay on the perimeter of the circle. A half circle from a vertex to a vertex has the diameter right, but the angle of the perimeter to the diameter is less than 90 degrees...
Anssi
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Its worth noting here that unless you follow Anssi's advice and create a circle with a number of sides divisible by 4, there will be NO point along any line or vertex in the circle that will correspond to the quadrant. Even referencing the center point of the circle and drawing out a radius to the edge will give you a smaller radius than the actual circle.
In Jean's example, the rotated circle/rectangle scenario only works because the circle was drawn orthogonal to the axis originally and then rotated afterward with the rectangle
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Well, at least it looks like nobody's getting fed up with me yet! Thank you for your great suggestions!
Chris, you didn't misunderstand -- your suggestion to copy a line and place it on the center of the circle was the easiest. Before responding to you, I ran over to SU to try it out, and got caught up in my drawing. Sorry -- you should have heard back from me last night. I appreciate the answer immensely!
Anssi, I tried making a circle with four segments and I got a square! Or a diamong/rhombus, really. Is there something I could have done to prevent the lines from becoming straight? Some key I could have held down to constrain the arcs to retain their curves? However, it occurred to me that I could make a square, or inscribe a square in my circle, and draw a bisecting line through the center of the circle, and then one of the sides of the square could serve as a line to copy and put in the center of the circle. Or maybe that's more trouble than it's worth.
And Jean, I checked out the tutorial, and at my level I find a still a bit confusing. I mean, I get it about inferencing the diameter from a nearby line that's parallel to the diameter I want, but that inferencing business still doesn't always work for me. It doesn't help that some of the text in the tut seems to be cut off, and there's no possibility of scrolling. I wish that some of the things the tut's writer talks about were shown, instead. But I'm sure with a few more weeks of playing under my belt, some of what he says will not be so arcane to me, anymore.
Mirjman, I noticed also that there was a reason it was working out so well in the tut. My circle segment did not have endpoints that fell so conveniently at the four quadrant points. I still think the borrowing of a line, and placing it at the center of the circle, is the best way for me to go.
I would have responded earlier to all this, but I wanted to try out the first suggestion, and got caught up in my drawing. Then life happened, and only now I'm back to play. Already feel like I've got a million more questions.... (sigh...)
Thanks so much, all of you!
Gigi
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Hi Gigi, hi folks.
Sorry for the text being cut off. I made that tutorial on an 19 inches monitor and, if viewed on anything smaller, it may produce that result. Simply zoom out to get the whole picture. You may also pan if required.
This tutorial is simply a SKP model using Scenes. Use the Scenes tab on top of the model window one by one and in numerical order in order to follow the development of the modeling.
When you have an inference that suits you, remember to press and hold the SHIFT key to lock it. While still maintaining the SHIFT key down you can continue with the drawing operation (line drawing for example).
For a parallel line, you use these steps:
1 - Find the starting point with the inference from the center of a circle.
2 - Click on the center to start the line.
3 - Place the cursor over a line that you would like to be parallel to. Wait for the pop-up stating "On edge".
4 - Place the cursor in such a way that you get a line attached to the staring point already defined and in a direction roughly parallel to the line inferenced at step 3. Wait for the magenta inference and the pop-up.
5 - Press and hold the SHIFT key to lock the inference.
6 - Move the cursor along the required direction and for the required length. Use the VCB, if required to specify the exact length.
7 - Click to set the end of the line.
8 - Release the SHIFT key.
Just ideas.
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