Tin

Class to encapsulate a tin made simply of arrays of points, triangles and adjacency information. Also methods to manipulate it.

class xms.grid.triangulate.Tin(points=None, triangles=None, **kwargs)
__init__(points=None, triangles=None, **kwargs)

Initialize self. See help(type(self)) for accurate signature.

adjacent_triangle(triangle_index, edge_idx)

Find the adjacent triangle from a triangle index and an edge

Parameters

  • triangle_index – index of the triangle

  • edge_idx – index of the edge

Returns

The triangle adjance to the triangle at the index or None if there isn’t one

property boundary_points

Indices of all points on any boundary, in no particular order

property boundary_polys

Exterior boundary and all interior voids as polygons of 0-based point indices. First point is not repeated as the last point.

build_triangles_adjacent_to_points()

Build array of triangles adjacent to points.

clear()

Clear the tin of all points, triangles, and triangles adjacent to points.

common_edge_index(triangle, adjacent_triangle)

Find common edge between triangle and neighbor

Parameters

  • triangle – triangle index

  • adjacent_triangle – adjacent triangle index

Returns

local index of the edge between the triange and adjacent_triangle if it exists, None otherwise.

delete_points(points)

Delete a list of points, update and renumber.

Parameters

points – Points to be deleted

delete_triangles(triangles)

Delete a list of triangles, update and renumber.

Parameters

triangles – Triangle to be deleted

export_tin_file(file_name)

Export in the .tin file format.

Parameters

file_name (str) – a file to write the tin to

property extents

The extents of the tin

global_index(triangle_idx, local_point)

Returns the global index of a point given the local index and a triangle

Parameters

  • triangle_idx – triangle to search

  • local_point – local index

Returns

global index of local_point in triangle_idx

local_index(triangle, point)

Returns index (0-2) of point within triangle given global index.

Parameters

  • triangle – triangle index

  • point – global point index

Returns

local index of the point in the triangle, or None if it is not part of the triangle

next_boundary_point(point)

Get the next point CW from point on the boundary. CCW if in an inside hole.

Parameters

point (int) – The starting point

Returns

The point index or None if not found

property number_of_points

Number of points in the tin

property number_of_triangles

Number of triangles in the tin

optimize_triangulation()

Swaps triangle edges until they are a Delauney triangulation.

Returns

True if modified, False otherwise

property points

Points in the tin

previous_boundary_point(point)

Get the previous point CCW from point on the boundary. CW if in an inside hole.

Parameters

point (int) – The starting point

Returns

The point index or None if not found

remove_long_thin_triangles_on_perimeter(ratio)

Removes long thin triangles on the boundary of the tin.

Parameters

ratio – The ratio of one edge length compared to the sum of the other two edge lengths. If the length ratio of a triangle is greater then or equal to this given ratio, the triangle is deleted.

Returns

True if successful, False otherwise

set_geometry(points, triangles, triangles_adjacent_to_points)

Set the geomoetry of the tin

Parameters

  • points – Points in tin

  • triangles – Triangles defining tin

  • triangles_adjacent_to_points – Triangles adjacent to points

swap_edge(triangle_a, triangle_b, check_angle=True)

Swap edges if triangles combine to form convex quad.

Parameters

  • triangle_a – First triangle

  • triangle_b – Second triangle

  • check_angle – Dont swap very thin triangles

Returns

True if successful False otherwise

triangle_adjacent_to_edge(point1, point2)

Gives triangle on the right side of the edge.

Parameters

  • point1 – first point of the edge

  • point2 – second point of the edge

Returns

The triangle adjacent to the edge.

triangle_area(triangle)

Calculate and return the area of a triangle.

Parameters

triangle (int) – Triangle index (0-based).

Returns

The area

triangle_centroid(triangle)

Calculate and return the centroid of a triangle.

Parameters

triangle (int) – Triangle index (0-based).

Returns

The centroid

triangle_from_edge(point1, point2)

Finds the triangle with the edge defined by an edge

Parameters

  • point1 – first point of edge

  • point2 – second point of edge

Returns

Triangle from an edge

property triangles

Triangles defining the tin

property triangles_adjacent_to_points

Triangles adjacent to points

triangulate()

Triangulate the tin

vertices_are_adjacent(point1, point2)

Check if vertices form an edge of a triangle

Parameters

  • point1 – first point index

  • point2 – second point index

Returns

True if points form a triangle edge, False otherwise.