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cpml.intersect.segment_segment fails to find intersects for some segments #90

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kromka-chleba opened this issue Aug 22, 2024 · 1 comment · May be fixed by #91
Open

cpml.intersect.segment_segment fails to find intersects for some segments #90

kromka-chleba opened this issue Aug 22, 2024 · 1 comment · May be fixed by #91

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@kromka-chleba
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I'm using CPML's cpml.intersect.segment_segment for finding road intersections in my Minetest mod and I noticed that CPML fails to find intersections for some of them. I compared CPML output with mlib's mlib.segment.getIntersection for the data and mlib finds them correctly.

Data for which CPML fails but mlib works:

Case 1

Seg1: {
	{
		y = -32,
		z = 97,
		x = 448
	},
	{
		y = -32,
		z = 13,
		x = 532
	}
}
Seg2: {
	{
		y = -32,
		z = -12,
		x = 524
	},
	{
		y = -32,
		z = 208,
		x = 524
	}
}
mlib: {
	y = -32,
	z = 21,
	x = 524
}
CPML: nil

Case 2

Seg1: {
	{
		y = -32,
		z = 290,
		x = 688
	},
	{
		y = -32,
		z = 353,
		x = 625
	}
}
Seg2: {
	{
		y = -32,
		z = 208,
		x = 524
	},
	{
		y = -32,
		z = 331,
		x = 647
	}
}
mlib: {
	y = -32,
	z = 331,
	x = 647
}
CPML: nil

Case 3

Seg1: {
	{
		y = -32,
		z = 290,
		x = 688
	},
	{
		y = -32,
		z = 353,
		x = 625
	}
}
Seg2: {
	{
		y = -32,
		z = 331,
		x = 647
	},
	{
		y = -32,
		z = 448,
		x = 647
	}
}
mlib: {
	y = -32,
	z = 331,
	x = 647
}
CPML: nil

Case 4

Seg1: {
	{
		y = -32,
		z = 928,
		x = 489
	},
	{
		y = -32,
		z = 805,
		x = 612
	}
}
Seg2: {
	{
		y = -32,
		z = 810,
		x = 621
	},
	{
		y = -32,
		z = 810,
		x = 448
	}
}
mlib: {
	y = -32,
	z = 810,
	x = 607
}
CPML: nil
@kromka-chleba
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kromka-chleba commented Aug 23, 2024 •
edited
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Okay, I did more tests and looks like cpml.intersect.line_line finds the intersection correctly but cpml.intersect.segment_segment fails. The reason behind this is that the latter function expects these segments to be component-wise min and max, which is totally weird because then cpml.intersect.line_line gets not the points of the segments but points with mixed components. Which is 1. incorrect 2. not documented anywhere.

I'll make a PR that fixes this soon, but I guess there are no buses in Gensokyo after all.

@kromka-chleba kromka-chleba linked a pull request Aug 23, 2024 that will close this issue
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intersect: Fix cpml.intersect.segment_segment bug, fixes #90 kromka-chleba/cpml
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@kromka-chleba