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73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/ellipse/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/ellipse/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/ellipse/blob/master/LICENSE)
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[](https://github.com/RobTillaart/ellipse/releases)
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# ellipse
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Arduino library with ellipse math
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## Description
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This experimental library provides basic ellipse math.
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It was written to test different perimeter algorithms.
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Trigger was a video of Dr. Matt Parker.
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https://www.youtube.com/watch?v=5nW3nJhBHL0
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## Interface
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- **ellipse(float a, float b)** constructor, a >= b
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- **float area()** returns the area of the ellipse.
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- **float circumference()** good algorithm (= Ramanujan 1).
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- **float eccentricity()** return the eccentricity e.
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This is an indication of flatness of the ellipse. 0 is a circle 1 is flat line.
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- **void setA(float a)** change the long radius.
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- **void setB(float b)** change the short radius.
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- **float getA()** return long radius of the ellipse.
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- **float getB()** return short radius of the ellipse.
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- **float getC()** distance to focus point form centre along the longer axis.
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#### Perimeter algorithms
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- **float perimeter_ref()** slower but best known algorithm (Ramanujan 2)
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- **float perimeter_Keppler()** good and fast algorithm for eccentricity between 1 and 2.
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- **float perimeter_Ramanujan1()** good algorithm.
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- **float perimeter_Ramanujan2()** slow but best known algorithm.
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See performance example for differences in timing.
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#### Misc
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- **bool isCircle(float epsilon = 0.0)** | a - b | < eps.
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- **bool isFlat()** true if a > 4b, where a = longest radius.
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#### Experimental
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- **float angle()** returns the angle if the ellipse was the
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shadow of a circle, Returns 0..90°, 0° == circle, 90° == line.
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## Operation
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See examples.
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## Future
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- make constructor symmetric (a < b or a > b ==> all possible.
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- make other code symmetric.
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- additional functions
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- Bresenham to draw ellipse?
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- documentation
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- refer Wikipedia.
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