From 025238c73f809683f63e739e3589e2e3ad16defb Mon Sep 17 00:00:00 2001
From: Cat Flynn <me@ktyl.dev>
Date: Wed, 2 Aug 2023 01:52:04 +0200
Subject: [PATCH] feat: render isocahedron

---
 CMakeLists.txt    |  1 +
 src/hello.cpp     | 10 +++++++--
 src/icosphere.cpp | 55 +++++++++++++++++++++++++++++++++++++++++++++++
 src/icosphere.hpp | 54 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 118 insertions(+), 2 deletions(-)
 create mode 100644 src/icosphere.cpp
 create mode 100644 src/icosphere.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c0bea94..2ab45ef 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -28,6 +28,7 @@ add_executable(${PROJECT_NAME}
     src/hello.cpp
     src/io.cpp
     src/triangle.cpp
+    src/icosphere.cpp
     src/gfx.cpp
 )
 
diff --git a/src/hello.cpp b/src/hello.cpp
index e0a1dca..e4bacb9 100644
--- a/src/hello.cpp
+++ b/src/hello.cpp
@@ -44,6 +44,7 @@
 
 #include "gfx.hpp"
 #include "triangle.hpp"
+#include "icosphere.hpp"
 
 #include <cmath>
 #include "astro/twoBodyMethods.hpp"
@@ -96,8 +97,11 @@ int main()
     if (initGraphics(&window) != 0)
         return -1;
 
-    Triangle triangle(compileShaderProgram());
+    GLuint shaderProgram = compileShaderProgram();
+    Triangle triangle(shaderProgram);
+    Icosphere sphere(shaderProgram, 0);
 
+    // Wireframe
     glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
 
     // Main loop
@@ -106,7 +110,9 @@ int main()
         glClearColor(0.2, 0.3, 0.3, 1.0);
         glClear(GL_COLOR_BUFFER_BIT);
 
-        triangle.render(glfwGetTime());
+        float time = glfwGetTime();
+        triangle.render(time);
+        sphere.render(time);
 
         glfwSwapBuffers(window);
         glfwPollEvents();
diff --git a/src/icosphere.cpp b/src/icosphere.cpp
new file mode 100644
index 0000000..d922bb4
--- /dev/null
+++ b/src/icosphere.cpp
@@ -0,0 +1,55 @@
+#include "icosphere.hpp"
+
+#include <iostream>
+
+Icosphere::Icosphere(GLuint shaderProgram, int subdivisions)
+	: _shaderProgram(shaderProgram)
+{
+	glGenVertexArrays(1, &_vao);
+	glGenBuffers(1, &_vbo);
+	glGenBuffers(1, &_ebo);
+
+	glBindVertexArray(_vao);
+
+	for (const auto& v : _isocahedronVertices)
+	{
+		_vertices.push_back(v[0]);
+		_vertices.push_back(v[1]);
+		_vertices.push_back(v[2]);
+	}
+	glBindBuffer(GL_ARRAY_BUFFER, _vbo);
+	glBufferData(GL_ARRAY_BUFFER, _vertices.size() * sizeof(float), &_vertices[0], GL_STATIC_DRAW);
+
+	for (const auto& tri : _isocahedronTriangles)
+	{
+		_indices.push_back(tri.vertex[0]);
+		_indices.push_back(tri.vertex[1]);
+		_indices.push_back(tri.vertex[2]);
+	}
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _ebo);
+	glBufferData(GL_ELEMENT_ARRAY_BUFFER, _indices.size() * sizeof(unsigned int), &_indices[0], GL_STATIC_DRAW);
+
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+	glEnableVertexAttribArray(0);
+
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+	glBindVertexArray(0);
+}
+
+void Icosphere::render(float time)
+{
+	glUseProgram(_shaderProgram);
+
+	glBindVertexArray(_vao);
+	glBindBuffer(GL_ARRAY_BUFFER, _vbo);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _ebo);
+
+	glDrawElements(GL_TRIANGLES, _indices.size(), GL_UNSIGNED_INT, 0);
+}
+
+Icosphere::~Icosphere()
+{
+    glDeleteVertexArrays(1, &_vao);
+    glDeleteBuffers(1, &_vbo);
+}
diff --git a/src/icosphere.hpp b/src/icosphere.hpp
new file mode 100644
index 0000000..b974282
--- /dev/null
+++ b/src/icosphere.hpp
@@ -0,0 +1,54 @@
+#pragma once
+
+#include <GL/glew.h>
+#include <vector>
+#include <string>
+
+#include "glm/glm.hpp"
+
+class Icosphere
+{
+public:
+	Icosphere(GLuint shaderProgram, int subdividision);
+	void render(float time);
+
+	~Icosphere();
+
+private:
+	GLuint _vbo;
+	GLuint _vao;
+	GLuint _ebo;
+	GLuint _shaderProgram;
+
+	std::vector<float> _vertices;
+	std::vector<unsigned int> _indices;
+
+	struct IcoTriangle
+	{
+		unsigned int vertex[3];
+	};
+
+	using IcoTriangleList = std::vector<IcoTriangle>;
+	using VertexList = std::vector<glm::vec3>;
+
+	const float X=.525731112119133606f;
+	const float Z=.850650808352039932f;
+	const float N=0.f;
+
+	const VertexList _isocahedronVertices =
+	{
+		{-X,N,Z}, {X,N,Z}, {-X,N,-Z}, {X,N,-Z},
+		{N,Z,X}, {N,Z,-X}, {N,-Z,X}, {N,-Z,-X},
+		{Z,X,N}, {-Z,X, N}, {Z,-X,N}, {-Z,-X, N}
+	};
+	 
+	const IcoTriangleList _isocahedronTriangles =
+	{
+		{0,4,1},{0,9,4},{9,5,4},{4,5,8},{4,8,1},
+		{8,10,1},{8,3,10},{5,3,8},{5,2,3},{2,7,3},
+		{7,10,3},{7,6,10},{7,11,6},{11,0,6},{0,1,6},
+		{6,1,10},{9,0,11},{9,11,2},{9,2,5},{7,2,11}
+	};
+
+	GLint getShaderUniformLocation(const std::string& uniformName);
+};
\ No newline at end of file