[opengl] 画一个可移动的自行车 二维几何变换（平移、旋转、缩放）

#include <cmath>

#include "glut.h"

#include "iostream"

using namespace std;

void init(void)

{

	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

	glClear(GL_COLOR_BUFFER_BIT);

	cout << "init.." << endl;

	glLineWidth(1.0f);

	glColor3f(1.0, 0.0, 0.0);

	glMatrixMode(GL_PROJECTION);//设置投影矩阵

	glLoadIdentity();

	gluOrtho2D(0.0, 600.0, 0.0, 600.0);//二维视景区域 左下角为原点

	//glClear(GL_COLOR_BUFFER_BIT);

	//glMatrixMode(GL_MODELVIEW);

	//glLoadIdentity();

}

int dir = 0;

int angle = 0;

// 绘制车轮

void DrawWheel(double x, double y, double r)

{

	int sec = 10;

	for (int i = 0; i <= sec; i++)

	{

		double delta = 3.1415926*2.0 / sec;

		glBegin(GL_LINE_LOOP);

		glVertex2f(x, y);

		glVertex2f(x + r * cos(delta*i), y + r * sin(delta*i));

		glVertex2f(x + r * cos(delta*(i + 1)), y + r * sin(delta*(i + 1)));

		glEnd();

	}

}

//绘制自行车

void DrawBike() {

	glClear(GL_COLOR_BUFFER_BIT);//清除窗口显示内容

	glColor3f(1.0f, 0.0f, 0);

	glPushMatrix();

	glTranslatef(100+dir, 124, 0);

	// 横车杆

	glBegin(GL_LINES);

	glVertex2f(0,0);

	glVertex2f(100,0);

	// 竖车杆

	glVertex2f(70, 0);

	glVertex2f(70, 30);

	// 车把

	glVertex2f(60, 30);

	glVertex2f(80, 30);

	glEnd();

	glPopMatrix();

	// 前车轮

	glPushMatrix();

	glTranslatef(100+dir, 100, 0);

	glRotatef(angle, 0, 0, 1);

	DrawWheel(0,0,25);

	glPopMatrix();

	// 后车轮

	glPushMatrix();

	glTranslatef(200+dir, 100, 0);

	glRotatef(angle, 0, 0, 1);

	DrawWheel(0, 0, 25);;

	glPopMatrix();

	glBegin(GL_LINES);

	glVertex2f(0, 75);

	glVertex2f(600, 75);

	glEnd();

	glutSwapBuffers();

}

void keyboard(unsigned char key, int x, int y)

{

	if (key == 'a')// 向左平移

	{

		cout << "左移" << endl;

		dir -= 10;

		angle += 10;

		glutPostRedisplay();//重绘窗口

	}

	if (key == 'd')// 向右平移

	{

		cout << "右移" << endl;

		dir += 10;

		angle -= 10;

		glutPostRedisplay();//重绘窗口

	}

}

void main(int argc, char** argv)

{

	glutInit(&argc, argv);

	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

	glutInitWindowPosition(300, 100);

	glutInitWindowSize(600, 600);

	glutCreateWindow("lab5");

	glutDisplayFunc(DrawBike);

	init();

	glutKeyboardFunc(keyboard);

	glutMainLoop();

}