[CG基础]

[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 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 #include 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 #include 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 #include 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;}

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