oepngl绘制cylinder，with two given 3d points

一同学需要绘制cylinder来代替由折线模拟曲线，之前简单的用过glucylidner函数，现在是需要 已知空间中两个三维点(x1,y1,z1, x2,y2,z2)已知，绘制过这两点的cylinder。

方法不难，这里收集了些网页。

1、http://www.thjsmith.com/40/cylinder-between-two-points-opengl-c

Vector3D a, b; (the two points you want to draw between)

// This is the default direction for the cylinders to face in OpenGL
Vector3D z = Vector3D(0,0,1);         
// Get diff between two points you want cylinder along
Vector3D p = (a - b);                               
// Get CROSS product (the axis of rotation)
Vector3D t = CROSS_PRODUCT (z , p); 

// Get angle. LENGTH is magnitude of the vector
double angle = 180 / PI * acos ((DOT_PRODUCT(z, p) / p.LENGTH());

//glTranslated(b.x,b.y,b.z);
glTranslated(a.x,a.y,a.z);
glRotated(angle,t.x,t.y,t.z);

gluQuadricOrientation(YourQuadric,GLU_OUTSIDE);
gluCylinder(YourQuadric, RADIUS, RADIUS, p.LENGTH(), SEGS1, SEGS2);

2、http://www.opengl.org/discussion_boards/showthread.php/144437-glucylinder-between-two-points

 
procedure CylinderGL(p1,p2:point3d;r1,r2:double;precision:integer);
var quadratic:pGLUquadricObj;
    height,dx,dy,dz:double;
    v,vx,vy,vz,rx,ry,ax,r2d:double;
    tmp:point3d;
begin
     if (p1.x=p2.x) and (p1.z=p2.z) and (p1.y<p2.y) then
     begin
          tmp:=p1;
          p1:=p2;
          p2:=tmp;
     end;
 
     r2d:=180/pi;
     //length of cylinder
     dx:=p1.x-p2.x;
     dy:=p1.y-p2.y;
     dz:=p1.z-p2.z;
     height:=sqrt(dx*dx+dy*dy+dz*dz);
 
     glpushmatrix;
     gltranslatef(p1.x,p1.y,p1.z);
 
	   // orientation vectors
	   vx:=p2.x-p1.x;	//	component in x-direction
	   vy:=p2.y-p1.y;	//	component in y-direction
	   vz:=p2.z-p1.z;	//	component in z-direction
 
     v:=sqrt(vx*vx+vy*vy+vz*vz);	// cylinder length
 
     // rotation vector, z x r
	   rx:=-vy*vz;
	   ry:=+vx*vz;
	   ax:=0.0;
     if vz=0 then
     begin
		      ax:=r2d*arccos(vx/v);	// rotation angle in x-y plane
		      if vx<=0 then ax:=-ax;
     end
     else
     begin
		      ax:=r2d*arccos(vz/v);	// rotation angle
		      if vz<=0 then ax:=-ax;
     end;
 
     if vz=0 then
     begin
			    glRotated(90.0, 0, 1, 0.0);			// Rotate & align with x axis
			    glRotated(ax, -1.0, 0.0, 0.0);		// Rotate to point 2 in x-y plane
     end
     else glRotated(ax, rx, ry, 0);			// Rotate about rotation vector
 
     //create a pointer to the quadric object
     quadratic:=gluNewQuadric;
     //tell it to smooth normals
	   gluQuadricNormals(quadratic, GLU_SMOOTH);
     //draw the clyinder
     gluCylinder(quadratic,r1,r2,height,precision,precision);		// Draw A cylinder
     glpopmatrix;
     //delete the pointer
     gluDeleteQuadric(quadratic);
end;