0.1.1 ellipse

Author: RobTillaart

libraries/ellipse/README.md

@@ -44,6 +44,18 @@ This is an indication of flatness of the ellipse. 0 is a circle 1 is flat line.
 See performance example for differences in timing.
 
 
+#### Misc
+
+- **bool isCircle(float epsilon = 0.0)**  | a - b | < eps.
+- **bool isFlat()** true if a > 4b, where a = longest radius.
+
+
+#### Experimental
+
+- **float angle()** returns the angle if the ellipse was the
+shadow of a circle, Returns 0..90°, 0° == circle, 90° == line.
+
+
 ## Operation
 
 See examples.
@@ -54,10 +66,10 @@ See examples.
 - make constructor symmetric (a < b or a > b ==> all possible.
 - make other code symmetric.
 - additional functions
-  - **bool isCircle()**  a == b
-  - **bool isFlat()**  a > 4 \* b ?
-  - bresenham to draw ellipse?
+  - Bresenham to draw ellipse?
+  - **float getLongRadius()**
+  - **float getShortRadius()**
+  - move all code to .cpp
 - documentation
-  - refer wikipedia.
-
+  - refer Wikipedia.
 

libraries/ellipse/ellipse.cpp

@@ -2,13 +2,16 @@
 //    FILE: ellipse.cpp
 //  AUTHOR: Rob Tillaart
 //    DATE: 2021-10-31
-// VERSION: 0.1.0
+// VERSION: 0.1.1
 // PURPOSE: Arduino library for ellipse maths
 //     URL: https://github.com/RobTillaart/ellipse
 // TRIGGER: https://www.youtube.com/watch?v=5nW3nJhBHL0
 //
 // HISTORY:
 //  0.1.0  2021-10-31  initial version
+//  0.1.1  2022-07-    add angle() + example
+//                     add isCircle(), isFlat()
+//                     update readme.md
 
 
 #include "ellipse.h"
@@ -79,12 +82,28 @@ float ellipse::area()
 
 float ellipse::eccentricity()
 {
+  if (_a == _b) return 0;  //  quick circle check.
   float x = _a * _a - _b * _b;
   if (x < 0) x = -1 * x;
   return sqrt(x)/ _a;
 }
 
 
+bool ellipse::isCircle(float epsilon)
+{
+  if (epsilon == 0) return (_a == _b);
+  float delta = abs(_a - _b);
+  return (delta < epsilon);
+}
+
+
+bool ellipse::isFlat()
+{
+  if (_a > _b) return (_a > (4 * _b));
+  return (_b > (4 * _a));
+}
+
+
 float ellipse::getC()
 {
   float e = eccentricity();
@@ -93,5 +112,11 @@ float ellipse::getC()
 }
 
 
+float ellipse::angle()
+{
+  float c = (_b < _a) ? _b/_a : _a/_b;
+  return acos(c) * (180 / PI);
+}
+
 // -- END OF FILE --
 

libraries/ellipse/ellipse.h

@@ -3,15 +3,15 @@
 //    FILE: ellipse.h
 //  AUTHOR: Rob Tillaart
 //    DATE: 2021-10-31
-// VERSION: 0.1.0
+// VERSION: 0.1.1
 // PURPOSE: Arduino library for ellipse maths
 //     URL: https://github.com/RobTillaart/ellipse
 //
 
 
 #include "Arduino.h"
 
-#define ELLIPSE_LIB_VERSION           (F("0.1.0"))
+#define ELLIPSE_LIB_VERSION           (F("0.1.1"))
 
 
 class ellipse
@@ -24,14 +24,22 @@ class ellipse
   float perimeter_Keppler();
   float perimeter_Ramanujan1();
   float perimeter_Ramanujan2();
+
   float eccentricity();
+  //  convenience functions.
+  bool  isCircle(float epsilon = 0.0);
+  bool  isFlat();   //  factor 4 ==>  < 15° 
 
   void  setA(float a) { _a = abs(a); };
   void  setB(float b) { _b = abs(b); };
   float getA()  { return _a; };
   float getB()  { return _b; };
   float getC();
 
+  //  experimental
+  //  returns the angle if the ellipse was the shadow of a circle.
+  float angle();
+
 private:
   float _a;
   float _b;

libraries/ellipse/examples/ellipse_angle/ellipse_angle.ino

@@ -0,0 +1,42 @@
+//
+//    FILE: ellipse_angle.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo
+//     URL: https://github.com/RobTillaart/ellipse
+//
+//  use the plotter tool to see the angle() curve.
+//
+
+#include "ellipse.h"
+
+
+ellipse el(1, 1);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.println();
+
+  for (int  a = 1; a <= 500; a++)
+  {
+    el.setA(1 + a * 0.002);
+    Serial.print(el.getB(), 2);
+    Serial.print('\t');
+    Serial.print(el.getA(), 4);
+    Serial.print('\t');
+    Serial.print(el.angle(), 4);
+    Serial.print('\n');
+  }
+
+  Serial.println("\nDone...");
+}
+
+
+void loop()
+{
+}
+
+
+// -- END OF FILE --

libraries/ellipse/keywords.txt

@@ -21,6 +21,8 @@ getA	KEYWORD2
 getB	KEYWORD2
 getC	KEYWORD2
 
+angle	KEYWORD2
+
 
 # Constants (LITERAL1)
 FLE_LIB_VERSION	LITERAL1

libraries/ellipse/library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/ellipse.git"
   },
-  "version": "0.1.0",
+  "version": "0.1.1",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*"

libraries/ellipse/library.properties

@@ -1,5 +1,5 @@
 name=ellipse
-version=0.1.0
+version=0.1.1
 author=Rob Tillaart <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=Arduino library for ellipse class