From 7749e5cda43a5417c53b6cfd5fe3914dc42063a0 Mon Sep 17 00:00:00 2001
From: ktyl <me@ktyl.dev>
Date: Fri, 13 Oct 2023 23:28:46 +0100
Subject: [PATCH] chore: extract retrieving cartesian elements

---
 src/orbit.cpp | 36 ++++++++++++++++++++++++------------
 src/orbit.hpp |  7 ++++++-
 2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/src/orbit.cpp b/src/orbit.cpp
index a6b10ef..2df3dec 100644
--- a/src/orbit.cpp
+++ b/src/orbit.cpp
@@ -45,11 +45,8 @@ void Orbit::setElements(Vector6 keplerianElements)
     regenerateVertices();
 }
 
-// Interpolate a position around the orbit.
-// t is in range 0..1 and wraps.
-glm::vec3 Orbit::getPosition(const float meanAnomaly)
+float Orbit::getEccentricAnomaly(const float meanAnomaly)
 {
-    // Get eccentric anomaly from elliptical mean anomaly
     const float eccentricity = _keplerianElements[astro::eccentricityIndex];
     float eccentricAnomaly = astro::convertEllipticalMeanAnomalyToEccentricAnomaly(
         eccentricity,
@@ -57,21 +54,36 @@ glm::vec3 Orbit::getPosition(const float meanAnomaly)
         (float)10e-3,
         100);
 
-    // Get true anomaly from eccentric anomaly
-    float trueAnomaly = astro::convertEccentricAnomalyToTrueAnomaly(
-        eccentricAnomaly,
-        eccentricity);
+    return eccentricAnomaly;
+}
 
-    std::vector<float> kepler(_keplerianElements);
-    kepler[astro::trueAnomalyIndex] = trueAnomaly;
-
-    std::vector<float> cartesian = astro::convertKeplerianToCartesianElements(kepler, 1.0);
+// Interpolate a position around the orbit.
+// t is in range 0..1 and wraps.
+glm::vec3 Orbit::getPosition(const float meanAnomaly)
+{
+    Vector6 cartesian = getCartesianCoordinates(meanAnomaly);
     return glm::vec3(
         cartesian[astro::xPositionIndex],
         cartesian[astro::yPositionIndex],
         cartesian[astro::zPositionIndex]);
 }
 
+float Orbit::getTrueAnomaly(const float meanAnomaly)
+{
+    const float eccentricAnomaly = getEccentricAnomaly(meanAnomaly);
+    const float eccentricity = _keplerianElements[astro::eccentricityIndex];
+    return astro::convertEccentricAnomalyToTrueAnomaly(
+        eccentricAnomaly,
+        eccentricity);
+}
+
+Vector6 Orbit::getCartesianCoordinates(const float meanAnomaly)
+{
+    Vector6 kepler(_keplerianElements);
+    kepler[astro::trueAnomalyIndex] = getTrueAnomaly(meanAnomaly);
+    return astro::convertKeplerianToCartesianElements(kepler, 1.0);
+}
+
 glm::vec3 Orbit::getTangent(const float meanAnomaly)
 {
     float epsilon = 0.01;
diff --git a/src/orbit.hpp b/src/orbit.hpp
index f717a61..1dd36ef 100644
--- a/src/orbit.hpp
+++ b/src/orbit.hpp
@@ -13,8 +13,9 @@ public:
     Orbit(Vector6 keplerianElements);
     void render();
 
+    // TODO: meanAnomaly in all these arguments actually means eccentricMeanAnomaly,
+    // will have to change that when adding non-ellipctical orbits - don't get confused!
     glm::vec3 getPosition(const float meanAnomaly);
-    glm::vec3 getVelocity(const float meanAnomaly);
     glm::vec3 getTangent(const float meanAnomaly);
 
     void setElements(Vector6 keplerianElements);
@@ -31,4 +32,8 @@ private:
     Vector6 _keplerianElements;
 
     void regenerateVertices();
+
+    float getEccentricAnomaly(const float meanAnomaly);
+    float getTrueAnomaly(const float meanAnomaly);
+    Vector6 getCartesianCoordinates(const float meanAnomaly);
 };