OpenGL编程 基础篇（三）用点集绘制函数

绘制函数 f(x) = e^(-x) * cos(2pi*x) 和 f(x) = e^|x| * cos(2pi * x)

#include "stdafx.h"
#include <windows.h>
#include <math.h>
#include <glGL.h>
#include <glglut.h>
const int screenWidth = 640;
const int screenHeight = 480;
GLdouble A,B,C,D;
//myInit
int abs(int x){ return x > 0 ? x : -x; }
void myInit(){
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glColor3f(0.0f, 0.0f, 0.0f);
    glPointSize(2.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble)screenWidth, 0.0, (GLdouble)screenHeight);
    A = screenWidth / 4.0;
    B = 0.0;
    //C = screenHeight / 2.0; //f(x) = e^(-x) * cos(2pi*x)的坐标变换 
　　 C = screenHeight / 32.0; //f(x) = e^|x| * cos(2pi * x)的坐标变换
    D = screenHeight / 2.0;
}
void myDisplay(){
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_POINTS);
    for (GLdouble x = 0.0; x < 4.0; x += 0.01)
    {
　　　　 //GLdouble func = exp(-x) * cos(2 * 33.1415927 * x);
        GLdouble func = exp(abs(-x)) * cos(2 * 3.1415926 * x);
        glVertex2d(A * x + B, C * func + D);
    }
    glEnd();
    glFlush();
}
void main(int argc,char ** argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(screenWidth, screenHeight);
    glutInitWindowPosition(100, 150);
    glutCreateWindow("Dot Plot of a Function");
    glutDisplayFunc(myDisplay);
    myInit();
    glutMainLoop();
    
}

运行截图：

   

                           f(x) = e^(-x) * cos(2pi*x)                                

                       　   f(x) = e^|x| * cos(2pi * x)   

说明：

1.这里采用的坐标是强制转换的，需要调整ABCD的值来使函数在显示窗口中央。其中fun1的A= 1/4.0 B = 0.0 C = 1/2.0 D = 1/2,0 ;func2 A = 1/4 B = 0.0 C = 1/32.0 D = 1/2.0

sx = A * x + B

sy = C * y + D

 2.将GL_POINTS 改为 GL_LINE_STRIP就变为“画线图”