/*constructive.c Constructive Solid Geometry*/

#include <GL/glut.h>
#include <stdlib.h>
#include <math.h>

void firstInsideSecond(void (*a) (void), void (*b) (void), GLenum face, GLenum test)
{
glEnable(GL_DEPTH_TEST);
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glCullFace(face); /* controls which face of a to use */
a(); /* draw a face of a into depth buffer */

/* use stencil plane to find parts of a in b */
glDepthMask(GL_FALSE);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 0, 0);
glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
glCullFace(GL_BACK);
b(); /* increment the stencil where the front face of b is drawn */

glStencilOp(GL_KEEP, GL_KEEP, GL_DECR);
glCullFace(GL_FRONT);
b(); /* decrement the stencil buffer where the back face
of b is drawn */
glDepthMask(GL_TRUE);
glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);

glStencilFunc(test, 0, 1);
glDisable(GL_DEPTH_TEST);

glCullFace(face);
a(); /* draw the part of a that's in b */
}


void fixDepth(void (*a) (void))
{
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
glEnable(GL_DEPTH_TEST);
glDisable(GL_STENCIL_TEST);
glDepthFunc(GL_ALWAYS);
a(); /* draw the front face of a, fixing the depth buffer */
glDepthFunc(GL_LESS);
}

/* "and" two objects together */
void and(void (*a) (void), void (*b) (void))
{
firstInsideSecond(a, b, GL_BACK, GL_NOTEQUAL);
fixDepth(b);
firstInsideSecond(b, a, GL_BACK, GL_NOTEQUAL);
glDisable(GL_STENCIL_TEST); /* reset things */
}

/* subtract b from a */
void sub(void (*a) (void), void (*b) (void))
{
firstInsideSecond(a, b, GL_FRONT, GL_NOTEQUAL);
fixDepth(b);
firstInsideSecond(b, a, GL_BACK, GL_EQUAL);
glDisable(GL_STENCIL_TEST); /* reset things */
}
 

#include "constructive.c"

class CMaSim
{
public:
...
void Subtract();
void RenderCutter();
void RenderObject();
...
}

void CMaSim::Subtract()
{
sub( RenderCutter, RenderObject); // <----- bi ba'o loi
} 

error C2664: 'sub' : cannot convert parameter 1 from 'void (void)' to 'void (__cdecl *)(void) 

void RenderCutter(CMaSim::*)(void)

void RenderCutter(*)(void)

• [*](Thông dụng) Thêm một member static, giả sử:
• Code:

• class CMaSim
  {
      public:
      void Subtract();
  	void RenderCutter();
      static void staticRenderCutter() {
      }
  	void RenderObject();
      static void staticRenderObject() {
      }
  };

• Lúc đó bạn gọi
• Code:

• sub(staticRenderCutter, staticRenderObject);

• như bình thường
• [*](Dễ dùng hơn) Dùng wrapper function, như thế này chẳng hạn
• Code:

• CMaSim *wrapperObj;
  
  void wrapperRenderCutter() {
  	return wrapperObj->RenderObject();
  }
  
  void wrapperRenderObject() {
  	return wrapperObj->RenderObject();
  }

• Lúc đó, bạn gọi:
• Code:

• sub( wrapperRenderCutter, wrapperRenderObject );

• là ổn