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Key error with local variant (11)

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Too hard mush Big Grin | :-D

We can’t stop here, this is bat country - Hunter S Thompson RIP

If your mush is too hard, use a ricer. This is mine: Grunwerg Commercial Grade Ricer[^] Makes mushed potato soooo easy. Wink | ;)

Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Like the solution it's currently unavailable Big Grin | :-D

We can’t stop here, this is bat country - Hunter S Thompson RIP

Maybe it'll appear in the next 37 minutes ... Laugh | :laugh:

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So what is it?

See above

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I got that cool app idea... It wouldn't have many customer, but it would have some and, to really shine, I just needed to solve one tiny (ahem) mathematical problems... Plus it would be like my.. mmm.. legacy? you know something, forgot the word, that shows your art and pride!

3 years and many frustration later (to be fair I spent more time playing video game than looking at it, since it's trauma inducing frustration) it isn't complete.. Cry | :((

At this stage the code looks almost simple and elegant (some method implementation are still scary though, some of them are 300 lines!) but it finally stumbled on what I guess looks strongly like... unavoidable mathematical rounding error...

It all starts with Bezier-Bezier curve intersection is an inexact science...
And it shows in unexpected place (or maybe dreadly expected hey?) when one does potato-potato intersections... Cry | :((

I don't want to give up.. but I have doubts.. Frown | :(

An idea just hit me... OMG | :OMG:

What if I made an article "a potato-potato intersection algorithm that almost work", would that attract the attention of challenge seeking programmer?
I would have to share sh*t ton of (undocumented) visualization code though (I dunno how much of my utility library I need to make it work, but just the low level visual classes are 100KB and 12 files)
And it's also part of what make my (unfinished) app looks great... Mmmm...

Or I could share the unit test code... but it's dreadfull and not conducive to creativity, it looks like that: OMG | :OMG:

(data was collected from a user friendly test app)

C#

[Fact]
public void ToughCut()
{
    var cutter = new Ring(new Element(new Point(130.783333333333, 199.310477598184)), new Element(new Point(127.38497431913, 199.310477598184), new Point(124.073849393798, 198.234627893256), new Point(121.32451919832, 196.237122582712)), new Element(new Point(118.575189002842, 194.239617272168), new Point(116.528801257989, 191.423006177879), new Point(115.478650569613, 188.190974692711)), new Element(new Point(114.428499881237, 184.958943207542), new Point(114.428499881237, 181.477420428821), new Point(115.478650569613, 178.245388943653)), new Element(new Point(116.528801257989, 175.013357458484), new Point(118.575189002842, 172.196746364196), new Point(121.32451919832, 170.199241053652)), new Element(new Point(124.073849393798, 168.201735743108), new Point(127.38497431913, 167.12588603818), new Point(130.783333333333, 167.12588603818)), new Element(new Point(131.219696969697, 167.12588603818)), new Element(new Point(134.6180559839, 167.12588603818), new Point(137.929180909233, 168.201735743108), new Point(140.678511104711, 170.199241053652)), new Element(new Point(143.427841300188, 172.196746364196), new Point(145.474229045041, 175.013357458484), new Point(146.524379733417, 178.245388943653)), new Element(new Point(147.574530421793, 181.477420428821), new Point(147.574530421793, 184.958943207542), new Point(146.524379733417, 188.190974692711)), new Element(new Point(145.474229045041, 191.423006177879), new Point(143.427841300188, 194.239617272168), new Point(140.678511104711, 196.237122582712)), new Element(new Point(137.929180909233, 198.234627893256), new Point(134.6180559839, 199.310477598184), new Point(131.219696969697, 199.310477598184)));
    var shape = new Shape(new Ring(new Element(new Point(12.7754813116188, -33.4128419451628), new Point(19.5223174580931, -29.9751572249652)), new Element(new Point(179.975157224965, 130.477682541907), new Point(183.412841945163, 137.224518688381)), new Element(new Point(185.725341896497, 151.825068758803), new Point(184.540796469908, 159.303994240127)), new Element(new Point(177.829660223277, 172.475340741641), new Point(172.475340741641, 177.829660223277)), new Element(new Point(159.303994240127, 184.540796469908), new Point(151.825068758803, 185.725341896497)), new Element(new Point(147.413657866616, 184.927395588484)), new Element(new Point(146.852379570287, 182.353400030402)), new Element(new Point(146.522877591701, 179.583755006682)), new Element(new Point(145.383023854803, 176.075645925844), new Point(144.229050444769, 174.093123340167)), new Element(new Point(141.746213714654, 171.399140511575)), new Element(new Point(139.217451805972, 169.454756076673), new Point(138.114716791943, 168.838299011114)), new Element(new Point(136.430867679513, 168.027334481522)), new Element(new Point(133.339495787831, 167.287179375534)), new Element(new Point(131.869596806395, 167.12588603818)), new Element(new Point(126.328777433712, 167.1807243084), new Point(125.140927792807, 167.390174249117)), new Element(new Point(120.57800049798, 170.108706697922)), new Element(new Point(-30.046677867818, 19.3819502930698), new Point(-33.4128419451628, 12.7754813116189)), new Element(new Point(-35.7253418964969, -1.82506875880269), new Point(-34.5407964699084, -9.30399424012683)), new Element(new Point(-27.8296602232773, -22.4753407416414), new Point(-22.4753407416414, -27.8296602232773)), new Element(new Point(-9.30399424012684, -34.5407964699084), new Point(-1.8250687588027, -35.7253418964969), new Point(5.47520627640808, -34.5690919208298))));

    var result = shape.Cut(cutter, 0.1);
    Assert.Single(result.Shapes);
}

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I think I would have a look at how others solved it, e.g. in the open source drawing program Inkscape $Shucks | :-\$

They have shape intersection?
(i.e. not polygon with straight line, but bezier side)

Excellent idea though, thanks! Smile | :)

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Super Lloyd wrote:
They have shape intersection?
(i.e. not polygon with straight line, but bezier side)

Well ... so does .NET: GraphicsPath.AddBeziers Method (System.Drawing.Drawing2D) | Microsoft Docs[^] And a Graphics path can be converted to a Region: Region Constructor (System.Drawing) | Microsoft Docs[^] And two regions can be Intersected: Region.Intersect Method (System.Drawing) | Microsoft Docs[^]

I'm not sure exactly what you are trying to use this for, so I don't know if it's relevant.

Sent from my Amstrad PC 1640
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This is not really helping...
Even if I were to give up on my classes and uses Region, once I do am Xor or Intersects.. there is no way to get the resulting Drawing.. i.e. no way to further manipulating the resulting shape (after, say an Xor) by having handle on its vertices...
It's a bit like the RichTextBox a completely opaque and not really customizable much solution to a complicated problem...

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I am gonna look but.. only because I am desperate... 112 files, 1.18Mb of C++ source code.. Blush | :O

For the record the text version of war and peace is less than 1 MB... OMG | :OMG:

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Lucky for you, the documentation is excellent Unsure | :~

Super Lloyd wrote:
1.18Mb of C++ source code..
For the record the text version of war and peace is less than 1 MB.

Compress em both then tell us which one is larger... Poke tongue | ;-P

From a purely psychological point of view I find it interesting that one of the qualities required to be a good programmer is the habit of obsessing over problems.
I find it interesting because the question is - at what point does that become unhealthy?

I mention this because I am learning python and as part of learning I am creating a bouncy ball program where a ball bounces off objects and its trajectory needs to conform with the effect of gravity.
I find the problem solving even finds its way into my dreams.
Anyway - I am not much help here, just an observation on the tendency we have to obsess over a problem until we solve it Smile | :)

“That which can be asserted without evidence, can be dismissed without evidence.”

― Christopher Hitchens

The Last Bug

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

That brings tears to my eyes! Big Grin | :-D

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I find that when I start dreaming about work, Then it is time to take some time off. Alittle Whiskey and little relaxing and then I start dreaming about things a guy should dream about(more whiskey, women and cars) and then the solution usually finds me

To err is human to really mess up you need a computer

GuyThiebaut wrote:
From a purely psychological point of view I find it interesting that one of the qualities required to be a good programmer is the habit of obsessing over problems.

There was an article on Ars a couple of weeks ago which describes programmers in a way that I find surprisingly accurate. Both from my personal experience and from watching some of my better developer coworkers.

Per Clive Thompson:[^]
... the pleasure that comes when you finally get things working is such a narcotic jolt. Coders will chase that thrill over and over again. It compensates for those brutal hours of frustration. So this is a class of people who are just amazingly good at pounding nails into the floorboard with their forehead.

If the problem were really accuracy, you could probably solve it by using a type such as double-double (giving approximately 32 decimal digits). I suspect, however, that the problem is of a different order.

I suggest that you look at W. Kahan's article Miscalculating Area and Angles of a Needle-like Triangle and at S. Boldo's article How to Compute the Area of a Triangle: A Formal Revisit. These may give you some pointers regarding the numerical issues involved in this sort of calculation.

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

To be fair, something that I haven't tried, is to change my custom epsilon (that I use to bound computation in bezier-bezier curve intersection, which could otherwise recurse like crazy) from 0.1 to a lower value.

But 0.1 should be enough, I think... (since Bezier curve are generated by hand, and if we omit the zoom, 1 pixel = 1 unit away = minimal relevant distance the user can draw, hence 0.1 should be pretty good. But I did zoom, that might have been the problem...)

Anyway, thanks for the links, gotta check them later....

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modified 22-Apr-19 20:38pm.

It's a graphics problem.
Jim Blinn probably has four solutions in his back pocket and just hasn't had time to publish them.
I'd ask him....

Point 7 from here seems to apply Seven Sins of the Eternal Dev | How to Make an RPG

Ask your self this: Is this a breaking issue that will completely stop the application from working?

No : release. get feedback. work on some other functionality. fix it in 2 years time.

(I write this before as a reflection to my self and getting over that first release hurdle.)

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“That which can be asserted without evidence, can be dismissed without evidence.”