<JordanBrown>
For a triangle: circle(r=..., $fn=3)
<JordanBrown>
One point will be at along the x axis at +r.
<JordanBrown>
The directly-opposite face will be at x=-r/2 (right)?
<JordanBrown>
That is, the total height of the triangle, from one of the faces to the opposite vertex, is 1.5*r, right?
<JordanBrown>
that should have been "(right?)", that is, asking whether my conclusion there was correct.
<InPhase>
Yeah. 360/3-90 = 30, so 30/60/90 triangle to the coordinate on the left, ((-1/2)*r, (sqrt(3)/2)*r)
<JordanBrown>
You mean the 30-60-90 triangle that results from dividing the triangle along the X axis?
<InPhase>
The one that results from the down the radial line to the origin, up along the y axis, and left out from there in the -x direction.
<InPhase>
It's not part of the larger triangle. Just the coordinate position triangle along the axis directions.
<InPhase>
All we need for it is the radius and that angle.
<JordanBrown>
I'm not seeing the triangle you are describing, but I think I have a construction that is simple enough that I'm understanding it. If you divide the big triangle into six parts by drawing a line from each vertex to the opposite face, each of those is 30-60-90 with the hypotenuse being r.
<JordanBrown>
The short side of those smaller triangles, the other side that leads from the center of the big triangle to the edge, is r/2.
<JordanBrown>
Thanks. Having somebody confirm my conclusion is very helpful. I'm not all that surprised that it's that simple, but I also wouldn't have been surprised if it was irrational.
<JordanBrown>
is the construction that convinced me
<JordanBrown>
Not quite as high production quality.
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<JordanBrown>
But my first attempt had gotten up to five measurements, and was confusing me.
<InPhase>
I like how you weave the support beams together for extra strength. ;)
<InPhase>
But yeah, I suppose that'll do it.
<JordanBrown>
I drew it in Paint instead of CorelDraw because Paint starts a lot faster. I should have used CorelDraw.
<Friithian>
you have a corel draw license?
<JordanBrown>
yes
<JordanBrown>
X3
<Friithian>
huh
<InPhase>
My physicist instincts are always to go to position vectors and axis components. Yours looks more like a math-reasoning approach.
<JordanBrown>
My formal math is all 40-something years old.
<JordanBrown>
I remember first principles OK, but have to re-derive everything else.
<InPhase>
I used gimp, which as you will note, after many decades of development, still has zero support for drawing an arc.
<InPhase>
The maintainers believe that is out of scope.
<JordanBrown>
There's an argument that they are right. It's an image manipulator, not a drawing tool.
<InPhase>
They want people to use other programs for that. (But there are no other good programs to do that well for this sort of purpose.)
<JordanBrown>
Inkscape.
<InPhase>
That's a program of desperation.
<JordanBrown>
:-)
<Friithian>
yeah I'd use inkscape for that
<JordanBrown>
I use CorelDraw for most such things, because I have it. There are some things I don't like about it, primarily when I'm trying to do scale drawings.
<InPhase>
When I need production quality figures like this, I use latexdraw, because inkscape is so hard to work with and so easy to destroy everything with.
<JordanBrown>
Inkscape is not as good, but also natively works with SVGs and I sometimes need that.
<Friithian>
inkscape is truely free, however
<JordanBrown>
I bought the Corel Home package back when it was a straight purchase (not subscription) and when there was not nearly as much free stuff available.
<Friithian>
my uni pays for adobe products, otherwise I'd have a license for corel for laser and plotter usage
<JordanBrown>
It kind of surprises me how neither CorelDraw nor Inkscape understand that there are *three* scales that are of interest: the size on the screen, the size on the paper, and the size of the thing being drawn. I think both of them only understand two of those scales.
<Friithian>
what do you mean?
<JordanBrown>
I want to draw the layout of my 350x108 foot yard, and I want to put it on an 8.5x11 inch piece of paper.
<JordanBrown>
So I want to say that one inch on the paper is, say, 30 feet.
<Friithian>
that is… not something I would put under a main usecase of these programs
<JordanBrown>
Maybe it's because what I have is a nail and so everything looks like a hammer, but they sure *seem* like drafting programs. Or at least they are close enough to be frustrating.
<Friithian>
they're general vector graphics drawing programs, drafting is somethng much more specific
<JordanBrown>
Yeah, I'd say drafting is a subset.
<JordanBrown>
I don't remember how each of them is deficient when I try to do that sort of drawing, but they do.
<JordanBrown>
It makes me want a 2D version of OpenSCAD.
<Friithian>
openscad does 2d though
<JordanBrown>
Only kind of.
<JordanBrown>
Only does polygons, not line segments.
<JordanBrown>
Yeah, you can fake line segments, but it's still fake.
<JordanBrown>
You can't easily draw two concentric circles.
<Friithian>
I feel like your hammer and nail analogy is true
<JordanBrown>
You could, by writing a "circle" module that really made a skinny version of whatever you call a flat torus.
<JordanBrown>
But the fact that you can't really do line segments and unfilled polygons is problematic.
<JordanBrown>
Also for 2D work it would be nice to lock the rotation so that you're always looking straight down.
<JordanBrown>
Thought I guess that's just "keep your finger off the left mouse button". :-)
<JordanBrown>
Hiding the Z axis would be nice.
<JordanBrown>
Hmm... orthogonal view, from +Z, does pretty well.
<JordanBrown>
InPhase - did you have a chance to look at the glossary that I put into one of the object-related issues? It seemed like we were having problems with keeping everybody on the same page because of terminology, so I wanted to try to nail that down.
<JordanBrown>
Or at least nail down as much as we could, so that we could focus on the parts that we couldn't nail don.
<JordanBrown>
(I am *so* spoiled by the ability to go back and edit your messages in Slack.)
<JordanBrown>
One of the unobvious things that may come out of the "object" work and some nearby stuff (like module literals and module references) may be helpful in the "how to structure libraries" picture.
<JordanBrown>
You could have an entire library be a single object, so that its entire namespace was only one top-level identifier.
<JordanBrown>
Say that it exported mylib; you could have modules mylib.pentagon() and mylib.dodecahedron(), and functions mylib.secant() and mylib.hyperbolic_arc_cosine().
<JordanBrown>
For extra credit, add import(scad-file), so that you could say mylib=import("mylib.scad") and the intrusion on the namespace would be entirely under the caller's control.
<JordanBrown>
There's a zillion details to work out, but the result seems like it might be fascinating... transformational, even.
<JordanBrown>
Time to go socialize with the spousal unit.
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<peepsalot>
<InPhase> [...] (But there are no other good programs to do that well for this sort of purpose.)
<peepsalot>
have you tried krita?
<peepsalot>
looks like a nice "paint" program, though I don't really have any experience with it either
<peepsalot>
or, for actual geometry-specific stuff, geogebra
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<InPhase>
peepsalot: I think I tried it, dismissed it as barely functional, and then forgot about it a looong time ago when it was fairly new. But yeah, maybe I should give that another fair shot. Thanks for the idea.
<Friithian>
krita is really good for drawing I have heard
<InPhase>
JordanBrown: I haven't yet. I'd been sleeping too little this week and needed to get back to a full night's worth. I am now recuperated, and should be able to think about the big picture questions of objects this evening. :)
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<JordanBrown>
GIMP may not be able to do arcs, but it's happy to do Bézier curves. You can also kind of do arcs by using Ellipse Select, then Stroke Selection, then erasing part of the resulting ellipse.
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<peepsalot>
you have to do ellipse twice (subtracting from selection the second time) if you want an arc line as opposed to a pie slice
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<peepsalot>
also i'm not sure if its trivial to get the exact same center the second time. idk, haven't tried in a long time because its a pain
<peepsalot>
oh, just saw you mention "stroke selection" which sounds like maybe would not require inner/outer ellipse, i don't think I've seen that before
<gbruno>
[github] thehans edited issue #4353 ("ERROR: Compilation aborted by exception: Unauthorized intersections of constraints" after enabling fast-csg) https://github.com/openscad/openscad/issues/4353
<JordanBrown>
The easiest way to get an arc-like shape in GIMP seems to be with the Bézier tool: ensure that "Polygonal" is not checked, then click one end of the arc, click the other end, click and drag the line and control points to form the desired arc, then Edit / Stroke Path / Stroke.
<JordanBrown>
Note that Bézier curves can only approximate circular arcs.
<linext>
i saw a demo of winamp milkdrop running in a web browser