TRIANGLE_INTERPOLATE is a C library which demonstrates some simple techniques for interpolating data on a triangle.
In the most common case, the value of a quantity is known at the vertices of a triangle, and a reasonable interpolated value is desired at some point p in the interior of that triangle. This can be done by linear interpolation.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
TRIANGLE_INTERPOLATE is available in a C version and a FORTRAN90 version and a MATLAB version and a Python version.
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You can go up one level to the C source codes.