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Go-Triangulation

This project was created to be able to fill complex forms in OpenGL in Go. The current library does not allow filling polygons completely. The gopxl/pixel/v2 library can fill a polygon with triangles but always refers to the 1st point of the polygon as one corner of the triangle, resulting in the obliteraten of parts under the top triangle.

This project shows a usage for a large file (.shp) to fill the country maps of the world. it fills 2127 entities, with a total of 25859 points using 58353 triangles in under 2s. (depending on your CPU) using the standard setting, with trim factor (see below) 0. other trimfactors could result in significant larger number of triangle !

Poly shape Triangulation example in OPENGL in GO

TriangMap uses Triangulate and ShpReader ShpReader reads SHP files used to construct maps. Maps are filled using Triangulation method For the executional version there are 3 optional parameters

  • "ShpFile", Default = "world.Shp", "Input shape file"
  • "TrimFactor", Default = 0, "Trim factor: 0 does not remove coordinates, any other number will trim points closer than a derived % to previous point, normal values are 1000 - 2000, this is done because for some models there are way to many points that are very close together and have no visual values in the end-result"
  • "Detail", Default = false, "True value shows triangle details in color variation per triangle"

Navigation of the map: Left, right, up, down arrow

Zoom: + or - key on numpad Scroll Zoom/Navigation with mouse scroll wheel Terminate with esc

The default SHP file is large, and shows most islands and territories over 1.000.000 triangles will be calculated. Any other map shape file is normally/of course significantly smaller.

The solution is not deterministic for all shapes due to the fact that in some cases some points will remain that can not create a triangle without inclusion of other points in the shape. Changing the TrimFactor can prevent/create the problem.