VC++实现的OpenGL线性渐变色绘制操作示例

#include <GL/glut.h>
#include <iostream>
#include <cmath>
using namespace std;
const GLsizei width=640;
const GLsizei height=480;//设置窗口的宽和高
void myInit()
{
  glClearColor(0,0,0,0);
}
void show()
{
  GLsizei dw;
  int n,i;
  dw=2;
  n=(width-1)/dw;
  cout<<"n="<<n<<endl;
  glClear(GL_COLOR_BUFFER_BIT);
  GLsizei r,g,b;
  for (i=0;i<n;i++)
  {
    //绘制应力云图的关键就是下面的这五种不同的颜色对应关系
    //根据自己需要可以设置不同的等级，四种也是可以的
    if (i>=0&&i<=n/5)
    {
      r=255;
      g=i*255/(n/5);
      b=0;
    }
    else if (i>n/5&&i<=2*n/5)
    {
      r=255-(i-n/5)*255/(n/5);
      g=255;
      b=0;
    }
    else if(i>2*n/5&&i<=3*n/5)
    {
      r=0;
      g=255;
      b=(i-2*n/5)*255/(n/5);
    }
    else if(i>3*n/5&&i<=4*n/5)
    {
      r=0;
      g=255-(i-3*n/5)*255/(n/5);
      b=255;
    }
    else
    {
      r=(i-4*n/5)*255/(n/5);
      g=0;
      b=255;
    }
    glColor3f(r/255.0f,g/255.0f,b/255.0f);
    glRectf(1.0*i*dw,0.0,1.0*(i+1)*dw,height);
  }
  glFlush();
}
void reshape(int w,int h)
{
  glViewport(0,0,(GLsizei)w,(GLsizei)h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0,w,0,h,-100,100);//设置视野的范围，(左,右,上,下,前,后)
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}
int main(int argc,char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
  glutInitWindowPosition(100,100);
  glutInitWindowSize(width,height);
  glutCreateWindow("应力云图绘制");
  myInit();
  glutDisplayFunc(show);
  glutReshapeFunc(reshape);
  glutMainLoop();
  return 0;
}