Dear All,
I have written a Delaunay triangulation 10 years ago
in C based on triangle structure.
It was 400 lines, so it seems to be a fine task to turn into python.
My problem is the translation of the C structure and the OO thinking.
I tried to draft it so.
/*
The triangle, its neighbours,
sides and rotations.
0
VTOP
/ \
/ t r \
LEFT/ o o \RIGHT 1
/ r t \
/ act \
1 VLEFT--------VRIGHT 2
BOTTOM
0
*/
typedef struct{
TRIINDEX neighbour[3]; // triangles: bottom, right, left
POINTINDEX vertex[3]; // vertex: top, left, right
float height; // elevation
} TRIANGLE;
Each triangle has three vertices and three neighbours.
To calculate the elvation on the triangulation at a given point,
it is important to find the coresponding triangle as fast as possible,
so the triangles had directions. But it was important in the update
process too.
So I had an array with the triangles, but the neighbours were
directed triangles not simple triangle (TRIINDEX).
There were C macros to get the neighbours of the triangles.
To get the left triangle tleft = LEFT(t), tright = RIGHT(t), tbottom =
BOTTOM(t)
ROT(t) was the same triangle as t, but rotated ccw.
so t = ROT(ROT(ROT(t)))
TOR(t) was the same triangle as t, but rotated cw.
t = TOR(TOR(TOR(t)))
In C, I have used
typedef unsigned int TRIINDEX;
to identify a triangle, where the last two bites were used to handle the
directions.
## I can translate it into python in this way
class Triangle:
def __init__(self, points, neighbours):
self.points = points
self.neighbours = neighbours
def TOR(self, direction):
return (self, (direction+1)%3)
def ROT(self, direction):
return (self, (direction+2)%3)
def RIGHT(self, direction):
return (self.neighbours[(direction+2)%3])
I would ask your opinions to encapsulate a triangle into a directed
triangle.
I made my first trial on the way to keep a directed triangle as a tuple
(triangle, direction)
and register it in that way.
I would like to use directed triangles, but wouldn't like to use too much
memory.
Yours sincerely,
Janos Juhasz
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