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| Time to revisit SVG path to LDraw conversion? |
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Posted by: N. W. Perry - 2022-12-08, 15:32 - Forum: LDraw File Processing and Conversion
- Replies (17)
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Yes, I'm thinking it's time!
Every pattern I create (which admittedly isn't that many yet) seems to involve passing through the SVG format at some point. But we're still missing a tool for converting SVG graphics directly to LDraw, and I know there have been a couple started already. (Img4Dat has planned SVG functionality, SvgToDat I believe handles basic primitives only, etc.)
My proposal is to start with the single task of converting SVG paths to vertices that can be imported, say, into LDPE at a reasonable resolution for mesh generation. And since SVG paths are really just a combination of cartesian coordinates (rel or abs) and Bezier control points, all that's really needed is a way to take the cubic Bezier math and make a polyline out of that—perhaps with an option between points evenly spaced, or according to curvature (so that tighter curves get more points). Best of all, that information is already stored in a nice, human-readable xml format within the svg file.
The use case for this arose when working on this part. I was able to lift those vectors directly from the official instruction booklet, put them into Inkscape, export a PNG and trace that manually in LDPE. But how much faster if I could have taken the paths themselves (or the xml data from inside the svg file) and drop them into a tool in LDPE, maybe adjust the precision a little bit, and instantly have the vertices I need to triangulate the pattern!
I'm thinking—in fact, I'm sure—that the math part of this has already been worked out many times over, and all that's missing is to code it in a way that's specific to LDraw. If we only focus on converting paths (which, again, is really just converting Bézier curves), then it think it becomes much easier to tackle than trying to incorporate the entire SVG spec into an LDraw tool, because a lot of that is probably stuff we can do more or less by hand.
So who's up for the challenge, and how can I help? I never learned to code, though I do understand programming languages generally. I just don't know a git from a commit from a pull request. ;-) And I'm not fluent in math, but I can figure out problems on an ad hoc basis, or at least look up the answers!
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| PT user accounts and authentication |
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Posted by: Orion Pobursky - 2022-12-05, 19:39 - Forum: Parts Tracker Discussion
- Replies (6)
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The PT currently uses the forums to authenticate users. While this currently works well enough, but with the next gen PT in development, we have an opportunity to discuss what we would like to do going forward.
I see 2 viable options:
- Keep the current system with the forums being the controlling account
Pros: Familiarity. Easier to PM authors with questions.
Cons: At the mercy of the developers of the forums to not break things. Rewrites needed if we decide to change software.
- The PT and the forum accounts separate
Pros: Thing only break if we break them. Having an API to tie into is easier.
Cons: More things to sign into. More difficult to tie stuff back to the forums (like the Parts Author badges)
Now that I've pondered and written the above, I think I'm in favor of keeping the forums and PT tied together.
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| Precise geometry vs fine-shading topology? |
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Posted by: Max Murtazin - 2022-12-03, 20:19 - Forum: Parts Authoring
- Replies (7)
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The topic that is bugging me a bit lately, is what should be really put in priority - precise geometry, or cutting down on that a bit, to have model be shaded way more nicely? Example of that would be the cut cylinder on the 50921. It features cylinder cut by the other one. In the current version, it looks like this:
The thin triangles lead to a pretty unpleasant shading, which essentially keeps edges very clear
It can be fixed by merging some of the vertices, but that results in cylinder not being really circular anymore:
I am not sure which approach is favorable. First result has pretty precise shaping, but loses in appearance. Second one is more fine in how it looks, and precision loss, while present, is not that dramatic
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| Matrix math for curved prims |
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Posted by: N. W. Perry - 2022-12-01, 19:19 - Forum: Parts Authoring
- No Replies
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Is it possible to get a rotation matrix for a circular primitive, given a simple (I guess quadratic) Bézier curve?
All of our curved prims are circles or conical, and I’ve read that any affine transformation of a conic section will result in another conic section. If the simple Bézier curves are likewise conic (which may be a wrong assumption), then theoretically they can all be represented by a 2D shear matrix, right?
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| Parts Tracker bug in release script (non-critical) |
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Posted by: Orion Pobursky - 2022-11-30, 4:42 - Forum: Parts Tracker Discussion
- Replies (1)
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I found a bug in the release script of the PT. If the first lines after the header are TEXMAP lines, the !HISTORY line for the release after those TEXMAP metas. I've currently found 6 affected parts in the Official Library:
parts/36069ap01.dat
parts/36069bp01.dat
parts/98088p01.dat
parts/98088p02.dat
parts/98088p03.dat
parts/98088p04.dat
If you find any more, let me know.
Note: This does not affect any visible aspects of the part. The only problem is that the header is out of compliance with the Header Spec.
I'll track the down the source of the bug and recycle the affected parts for the 2022-06 release.
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