Creating a Rotating Sphere in C Language

To represent complex surfaces in a computer, we usually adopt a method called meshing. This means discretizing the surface into a series of small flat pieces, each of which is a simple geometric shape, such as quadrilaterals or triangles. In this way, we can approximate the original surface using these simple flat shapes.

The accuracy of the mesh determines how well it approximates the surface. The finer we subdivide the surface, the more quadrilaterals or triangles we need to fill these small areas. This means that the representation of the surface in the computer will be closer to its actual shape, and it will appear smoother.

However, this process of refinement also brings computational challenges. As the mesh density increases, we need to handle more quadrilaterals or triangles, which can lead to a significant increase in computational workload and slower processing speed.

Therefore, in practical applications, it is necessary to strike a balance between accuracy and computational efficiency. Choosing the appropriate mesh density to achieve the desired approximation effect while ensuring computational efficiency and performance is essential.

Below is a dynamic sphere drawing:

#include<graphics.h>#include<math.h>#include<stdio.h>#include<conio.h>
#define PI acos(-1.0)void HideSphere(float R,int alfa,int beta,int HideFlag);
int main(){  initgraph(640, 480);  BeginBatchDraw();   while (true)  {    for (int i = 0; i < 180; i++)    {      HideSphere(200, 45 + i, 30 + i, 1);      Sleep(20);      FlushBatchDraw();      cleardevice();    }  }  EndBatchDraw();  _getch();}
void HideSphere(float R, int alfa, int beta, int HideFlag){  int i, j, k;  float x[4], y[4], z[4], x1[4], y1[4], z1[4], sx[4], sy[4];  double a1, a2, b1, b2, c, d, xn, yn, zn, vn;  c = alfa * PI / 180.0;  d = beta * PI / 180.0;  for (j = 0; j < 180; j = j + 5)  {    a1 = j * PI / 180.0;    a2 = (j + 5) * PI / 180.0;    for (i = 0; i < 360; i = i + 5)    {      b1 = i * PI / 180.0;      b2 = (i + 5) * PI / 180.0;      x[0] = R * sin(a1) * cos(b1); y[0] = R * sin(a1) * sin(b1); z[0] = R * cos(a1);      x[1] = R * sin(a2) * cos(b1); y[1] = R * sin(a2) * sin(b1); z[1] = R * cos(a2);      x[2] = R * sin(a2) * cos(b2); y[2] = R * sin(a2) * sin(b2); z[2] = R * cos(a2);      x[3] = R * sin(a1) * cos(b2); y[3] = R * sin(a1) * sin(b2); z[3] = R * cos(a1);      for (k = 0; k < 4; k++)      {        x1[k] = x[k] * cos(c) - y[k] * sin(c);        y1[k] = x[k] * sin(c) * cos(d) + y[k] * cos(c) * sin(d) + z[k] * sin(d);        z1[k] = -x[k] * sin(c) * sin(d) - y[k] * cos(c) * sin(d) + z[k] * cos(d);        sx[k] = 320 - x1[k];        sy[k] = 240 - z1[k];      }      xn = (y1[2] - y1[0]) * (z1[3] - z1[1]) - (y1[3] - y1[1]) * (z1[2] - z1[0]);      yn = -(x1[2] - x1[0]) * (z1[3] - z1[1]) + (x1[3] - x1[1]) * (z1[2] - z1[0]);      zn = (x1[2] - x1[0]) * (y1[3] - y1[1]) - (x1[3] - x1[1]) * (y1[2] - y1[0]);      vn = sqrt(xn * xn + yn * yn + zn * zn);      xn = xn / vn;      yn = yn / vn;      zn = zn / vn;      if (!HideFlag || yn >= 0.0)      {        moveto(sx[0],sy[0]);        lineto(sx[1],sy[1]);        lineto(sx[2],sy[2]);        lineto(sx[3],sy[3]);        lineto(sx[0],sy[0]);      }    }  }

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