From 80ddb7dd8289a44c034d523d56231b02ec1a55ed Mon Sep 17 00:00:00 2001
From: Cat Flynn <me@ktyl.dev>
Date: Sun, 6 Aug 2023 15:20:22 +0200
Subject: [PATCH] feat: draw orbit with astro

---
 src/hello.cpp |  2 +-
 src/orbit.cpp | 27 ++++++++++++++++-----------
 src/orbit.hpp |  2 +-
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/src/hello.cpp b/src/hello.cpp
index fcaa096..a783abb 100644
--- a/src/hello.cpp
+++ b/src/hello.cpp
@@ -155,7 +155,7 @@ int main()
     GLuint unlitProgram = compileShaderProgram("./frag_unlit.glsl");
 
     Icosphere sphere(0.5, 2);
-    Orbit orbit(30, glm::vec3(.5, .5, 0));
+    Orbit orbit(100);
 
     // Main loop
     while (!glfwWindowShouldClose(window))
diff --git a/src/orbit.cpp b/src/orbit.cpp
index 6bee57a..1ed4758 100644
--- a/src/orbit.cpp
+++ b/src/orbit.cpp
@@ -1,28 +1,33 @@
 #include "orbit.hpp"
 
-#include "glm/gtx/quaternion.hpp"
+#include "astro/stateVectorIndices.hpp"
+#include "astro/orbitalElementConversions.hpp"
 
-Orbit::Orbit(int vertexCount, glm::vec3 up)
+Orbit::Orbit(int vertexCount)
 {
     const float pi = 3.14159265359;
-    const glm::vec3 worldUp = glm::vec3(0.0, 1.0, 0.0);
 
-    // Compute the rotation between world 'up' and our defined up
-    glm::quat rot = glm::rotation(worldUp, normalize(up));
+    std::vector<float> keplerianElements(6);
+    keplerianElements[astro::semiMajorAxisIndex] = .75;
+    keplerianElements[astro::eccentricityIndex] = .1;
+    keplerianElements[astro::inclinationIndex] = pi / 2.0 + 0.1;
+    keplerianElements[astro::argumentOfPeriapsisIndex] = 0;
+    keplerianElements[astro::longitudeOfAscendingNodeIndex] = 0;
 
     for (int i = 0; i < vertexCount; i++)
     {
         float a = (float)i / (float)vertexCount;
         a *= 2.0 * pi;
 
-        glm::vec3 v = glm::vec3(cos(a), 0.0, sin(a));
+        keplerianElements[astro::trueAnomalyIndex] = a;
 
-        // Rotate generated point to align with new up vector
-        v = rot * v;
+        std::vector<float> cartesian = astro::convertKeplerianToCartesianElements(
+            keplerianElements,
+            1.0);
 
-        _vertices.push_back(v.x);
-        _vertices.push_back(v.y);
-        _vertices.push_back(v.z);
+        _vertices.push_back(cartesian[astro::xPositionIndex]);
+        _vertices.push_back(cartesian[astro::yPositionIndex]);
+        _vertices.push_back(cartesian[astro::zPositionIndex]);
     }
 
     glGenVertexArrays(1, &_vao);
diff --git a/src/orbit.hpp b/src/orbit.hpp
index 3bc15d1..a9773e9 100644
--- a/src/orbit.hpp
+++ b/src/orbit.hpp
@@ -8,7 +8,7 @@
 class Orbit
 {
 public:
-    Orbit(int vertexCount, glm::vec3 up);
+    Orbit(int vertexCount);
     void render();
     ~Orbit(); 
 private: