OpenGL基礎（一）2. 畫多邊形之顏色漸變的圓 月食效果

文章原創 轉載請標明出處
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畫圓的函數中 RGB顏色值變化
幾種效果展示
黑白色

void drawCircle(GLdouble radius, GLdouble divide)
{
    
    for (int k = 0; k < divide; k++) { x = radius* cos((k / divide) * 2 * PI); y = radius* sin((k / divide) * 2 * PI); glColor3f((k/divide), (k / divide), (k / divide)); glVertex3d(x, y, 0.0); } }

翠綠色 

 1 void drawCircle(GLdouble radius, GLdouble divide)
 2 { 3 4 for (int k = 0; k < divide; k++) 5  { 6 x = radius* cos((k / divide) * 2 * PI); 7 y = radius* sin((k / divide) * 2 * PI); 8 glColor3f((k / divide), 1.0, (k / divide)); 9 glVertex3d(x, y, 0.0); 10  } 11 }

紫色

glColor3f((k / divide), 0.0, (k / divide) );

 

完整程序代碼如下

//Five edges polygon.
//As less code as possible.

#include "stdafx.h"
#include<gl/glut.h>
#include<stdlib.h>
#include<iostream>
#include<math.h>

const GLdouble PI = 3.1415926;
static GLdouble x, y;
using namespace std;

void drawCircle(GLdouble radius, GLdouble divide)
{
    
    for (int k = 0; k < divide; k++)
    {
        x = radius* cos((k / divide) * 2 * PI);
        y = radius* sin((k / divide) * 2 * PI);
        glColor3f(0.5*(k / divide), (k / divide), (k / divide) );
        glVertex3d(x, y, 0.0);
    }
}

void init(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);


    glBegin(GL_POLYGON);
    
    drawCircle(0.8, 100);

    glEnd();
    glFlush();

}


int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowPosition(500, 300);
    glutInitWindowSize(500, 500);
    glutCreateWindow("DrawGeometry");
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}