[CG基础]

1.窗口界面的显示，400*300像素大小的窗口，四个角有四个红色的点。

#include "stdafx.h"#include <gl/glut.h>void display(void){glClear(GL_COLOR_BUFFER_BIT);glColor3f(1.0, 0.0, 0.0);glBegin(GL_POINTS);glVertex2i(0, 0);glVertex2i(0, 299);glVertex2i(399, 0);glVertex2i(399, 299);glEnd();glFlush();}int main(int argc,char**argv){glutInit(&argc, argv);//对GLUT初始化，随后调用三个函数指定即将建立的推向视窗的特征glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//设置图形显示模式，要求系统为图像提供一个单独的RGB帧缓冲器glutInitWindowSize(400, 300);//设置图形大小400*300个像素点glutInitWindowPosition(200, 100);glutCreateWindow("sample");glClearColor(0.0, 0.0, 0.0,0.0);gluOrtho2D(0.0, 400.0, 0.0, 300.0);//次函数为照相机取景框。glutDisplayFunc(display);glutMainLoop();    return 0;}

2.画一个心形线，其方程为r=1-cos0。

// ConsoleApplication1.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <gl/glut.h>#include <math.h>GLfloat r(double angle){return 1 - cos(angle);}void display(void){double t, p = 3.141593 / 180;glClear(GL_COLOR_BUFFER_BIT);glColor3f(1.0, 0.0, 0.0);glBegin(GL_POINTS);for (int i = 0; i < 360; i += 4) {t = i*p;glVertex2f(r(t)*cos(t), r(t)*sin(t));}glEnd();glFlush();}int main(int argc,char**argv){glutInit(&argc, argv);//对GLUT初始化，随后调用三个函数指定即将建立的推向视窗的特征glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//设置图形显示模式，要求系统为图像提供一个单独的RGB帧缓冲器glutInitWindowSize(400, 300);//设置图形大小400*300个像素点glutInitWindowPosition(200, 100);glutCreateWindow("sample");glClearColor(0.0, 0.0, 0.0,0.0);gluOrtho2D(-2.0, 2.0, -1.5, 1.5);//次函数为照相机取景框。glutDisplayFunc(display);glutMainLoop();    return 0;}

并可以同在在glBegin函数前添加glPointSize(5.0);改变画笔像素宽度

通过添加reshape函数保持窗口比例变化时，图形比例不变。glViewport（0，0，width，height）是保持视区与调整后图像一致。

并在glutDisplayFunc(display)后面添加glutReshapeFunc(reshape);reshape函数还是比较好理解的，当比例不对时，重新设置其视区。

void reshape(GLsizei width, GLsizei height) {float w_aspect = 4.0 / 3.0, aspect = ((float)width) / height;if (aspect <= w_aspect)glViewport(0, (height - width / w_aspect) / 2, width, width / w_aspect);else glViewport((width - height*w_aspect) / 2, 0, height*w_aspect, height);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(-2.0, 2.0, -1.5, 1.5);}

4.Mandelbrot虫图像的显示：

原理呢，根据变换公式xn+1=xn^2+z，Mandelbrot集是指x从0起点利用公式变换不导致发散的全体负数z的集合。

// ConsoleApplication1.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <gl/glut.h>#include <math.h>int width = 400;int height = 400;int Mandelbrot(double a, double b, int n) {double x = 0, y = 0, xx = 0, yy = 0;int i = 0;while (i++ < n){y = 2 * x*y + b;x = xx - yy + a;xx = x*x;yy = y*y;if ((xx + yy) > 4) return i;}return 0;}void display(void){double min_a, max_a, min_b, max_b, step_b, step_a, a, b;int c, n = 64;float scale = 255.0 / n;min_a = -2.0;max_a = 0.5;min_b = -1.25;max_b = 1.25;step_a = (max_a - min_a) / width;step_b = (max_b - min_b) / height;glClear(GL_COLOR_BUFFER_BIT);glBegin(GL_POINTS);a = min_a;for (int x = 0; x < width; x++) {b = min_b;for (int y = 0; y < height; y++) {c = 255- scale*Mandelbrot(a, b, n);glColor3ub(c, c, c);glVertex2i(x, y);b += step_b;}a += step_a;}glEnd();glFlush();}/*void reshape(GLsizei width, GLsizei height) {float w_aspect = 4.0 / 3.0, aspect = ((float)width) / height;if (aspect <= w_aspect)glViewport(0, (height - width / w_aspect) / 2, width, width / w_aspect);else glViewport((width - height*w_aspect) / 2, 0, height*w_aspect, height);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(-2.0, 2.0, -1.5, 1.5);}*/int main(int argc,char**argv){glutInit(&argc, argv);//对GLUT初始化，随后调用三个函数指定即将建立的推向视窗的特征glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//设置图形显示模式，要求系统为图像提供一个单独的RGB帧缓冲器glutInitWindowSize(400, 400);//设置图形大小400*300个像素点glutInitWindowPosition(200, 100);glutCreateWindow("sample");glClearColor(0.0, 0.0, 0.0,0.0);gluOrtho2D(0.0, 400.0, 0.0, 400.0);//次函数为照相机取景框。glutDisplayFunc(display);//glutReshapeFunc(reshape);glutMainLoop();    return 0;}

将z设为固定值，得到一个Julia集的不发散数。

// ConsoleApplication1.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <gl/glut.h>#include <math.h>int width = 400;int height = 300;int Julia(double x, double y, int n){double xx, yy, p = -0.7454, q = 0.1131;int i = 0;xx = x*x;yy = y*y;while (i++ < n) {y = 2 * x*y + q;x = xx - yy + p;xx = x*x;yy = y*y;if ((xx + yy) > 4) return i;}return 0;}void display(void){double min_a, max_a, min_b, max_b, step_b, step_a, a, b;int c, n = 180;float scale = 255.0 / n;min_a = -1.6;max_a = 1.6;min_b = -1.2;max_b = 1.2;step_a = (max_a - min_a) / width;step_b = (max_b - min_b) / height;glClear(GL_COLOR_BUFFER_BIT);glBegin(GL_POINTS);a = min_a;for (int x = 0; x < width; x++) {b = min_b;for (int y = 0; y < height; y++) {c = 255- scale*Julia(a, b, n);glColor3ub(c, c, c);glVertex2i(x, y);b += step_b;}a += step_a;}glEnd();glFlush();}int main(int argc,char**argv){glutInit(&argc, argv);//对GLUT初始化，随后调用三个函数指定即将建立的推向视窗的特征glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//设置图形显示模式，要求系统为图像提供一个单独的RGB帧缓冲器glutInitWindowSize(width, height);//设置图形大小400*300个像素点glutInitWindowPosition(200, 100);glutCreateWindow("sample");glClearColor(0.0, 0.0, 0.0,0.0);gluOrtho2D(0.0, 400.0, 0.0, 300.0);//次函数为照相机取景框。glutDisplayFunc(display);glutMainLoop();    return 0;}

当然可以添加颜色：将函数改为glColor3ub(red(c), green(c), blue(c));

int red(int c) {if (c <= 160)return 0;else if (c < 224) return (c - 160) * 4;else return 255;}int green(int c){if (c <= 64) return 0;else if (c < 128) return (c - 64) * 4;else if (c < 192) return 255;else return (255 - c) * 4;}int blue(int c){if (c < 64) return c * 4;else if (c <= 96) return 255;else if (c <= 160) return(160 - c) * 4;else return 0;}