オリンピックの図形を描く

olympic.cpp

#define GLFW_INCLUDE_GLU
#define _USE_MATH_DEFINES //M_PIを使うためのおまじない
#include <gl/glfw3.h> //某大の教授が開発したっぽいChinouGLとやらの代わりにGLFWを使う(ChinouGLはググっても情報が出てこなかった)
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <string>

#define LENGTH_OF(TS) (sizeof(TS) / sizeof(TS[0]))//配列のサイズを求める

GLFWwindow* window;

const int HEIGHT = 480;
const int WIDTH = 640;

typedef struct hCircle{
	int x;int y;int z;
	int outer_radius;int inner_radius;
	int start_degree;int end_degree;
	float red;float green;float blue;
} hCircle_t;

const hCircle_t OLYMPIC[] = {
	{448,272,-40,60,50,-45,135,1.0f,0.0f,0.0f},//赤うえ
	{384,208,-30,60,50,225,405,0.0f,1.0f,0.0f},//緑した
	{448,272,-20,60,50,135,315,1.0f,0.0f,0.0f},//赤した
	{256,208,-10,60,50,225,405,1.0f,1.0f,0.0f},//黄した
	{320,272,0,60,50,135,315,1.0f,1.0f,1.0f},//白した
	{384,208,10,60,50,45,225,0.0f,1.0f,0.0f},//緑うえ
	{320,272,20,60,50,-45,135,1.0f,1.0f,1.0f},//白うえ
	{192,272,30,60,50,135,315,0.0f,0.0f,1.0f},//青した
	{256,208,40,60,50,45,225,1.0f,1.0f,0.0f},//黄うえ
	{192,272,50,60,50,-45,135,0.0f,0.0f,1.0f},//青うえ
};

//OpenGL周りの初期化
bool Initialize(){

  if (!glfwInit()) return false;

  window = glfwCreateWindow(640, 480, "OpenGL Window", nullptr, nullptr);
  if (!window) {
    glfwTerminate();
    return false;
  }

  glfwMakeContextCurrent(window);
  return true;
}

//ウィンドウ左下が原点
void glStart(){
	int width, height;
    glfwGetFramebufferSize(window, &width, &height);
    float ratio = width / (float) height;
    glViewport(0, 0, width, height);
    glClear(GL_COLOR_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0f, width, 0.0f, height, 1000.0f, -1000.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

//かまぼこの赤い部分みたいな図形を描くよ
//xとyは円の中心の座標だよ。
void drawHollowCircle(int x,int y,int z, int outer_radius,int inner_radius, int start_degree,int end_degree, float red,float green,float blue){
	if(start_degree > end_degree) return;//start_degreeの方が大きいのはダメ

	glBegin(GL_TRIANGLE_STRIP);
    glColor3f(red,green,blue);

	int diff_degree = (end_degree - start_degree);

	//円の外側の頂点
	for(int i=0;i <= diff_degree;i++){
		float angle = (float)(M_PI*2.0*(i+start_degree))/360.0f; //degreeをradianに変換
		glVertex3f(outer_radius * cos(angle) + x,
				   outer_radius * sin(angle) + y, z);

		glVertex3f(inner_radius * cos(angle) + x,
				   inner_radius * sin(angle) + y, z);
	}

    glEnd();
}

int main()
{
  if(!Initialize()){
	  return -1;//初期化に失敗したのでプログラム終了
  }
  while(!glfwWindowShouldClose(window)){
      glStart();

	  glTranslatef(WIDTH/2,0.f,0.f);
	  glRotatef((float) sin(glfwGetTime()*2)*60, 0.f, 1.0f, 0.f);//何となく回転させてみる
	  glTranslatef(-WIDTH/2,0.f,0.f);

	  for(int i=0;i < LENGTH_OF(OLYMPIC);i++){
		  hCircle_t c = OLYMPIC[i];
		  drawHollowCircle(c.x,c.y,c.z, c.outer_radius,c.inner_radius, c.start_degree,c.end_degree, c.red,c.green,c.blue);
	  }

	  glfwSwapBuffers(window);
      glfwPollEvents();
  }
  
  glfwTerminate();
  
  return 0;
}