add polygon_chord#2969
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Maybe we should consider adding shapely as a dependency? It might simplify some of these computations without having to re-implement all of computational geometry. |
I already looked into using shapely for a way to support trigger / voltage patches in the past here: |
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This is possible, but the function itself is very small, so using an external library would be unnecessary. I wouldn’t make it more complex than it is. |
| X-coordinates of the starting points of the polygon edges. | ||
| ri_y : ndarray of shape (N,) | ||
| Y-coordinates of the starting points of the polygon edges. | ||
| vi_x : ndarray of shape (N,) |
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I think we should deduce these (if needed) from the vertices. You can write a helper for this.
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Yes, I'd also prefer the vertices as input. But maybe the function as it is here is fine and that transformation is made once outside of this function.
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| Parameters | ||
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| mu_x : float |
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These should be quantities, as we discussed offline, the best would be to use telescope coordinate system lat/lon.
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Also, perhaps tuples of (x,y) or arrays of them would be more straightforward to define points (arrays of points)
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| Returns | ||
| ------- | ||
| float |
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Should be also a unit of length (or angular, equivalent in the telescope frame)
| - Each polygon edge is defined as: | ||
| (x, y) = (ri_x, ri_y) + t * (vi_x, vi_y), with 0 <= t < 1 | ||
| - The function computes intersections by solving a 2D linear system. | ||
| - A small epsilon_d (`1e-20`) is added to the denominator to avoid division by zero. |
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why not using
try:
...
except ZeroDivisionError:
# determinant is zero, the cord goes on the edge, handle this
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Just remember that catching an exception is quite a bit slower than adding an epsilon, so if you need this to be fast, the epsilon method might be better. Also if you want to use numba to speed things up
| SQRT2 = np.sqrt(2) | ||
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| def polygon_chord(mu_x, mu_y, phi, ri_x, ri_y, vi_x, vi_y): |
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This function should be njit, as it will be called. If possible, it would also be good if it could be vectorized over multiple tiles.
4 participants
Polygonal description of the chord.
096_arbitrary_shaped_mirror_and_polygon_chord.pdf
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