3D- rotaion and zoom in/out pan function in opengl

More seriously, you can find an example about one regular cube rotation where you can select the axis of rotation
with the mouse's buttons at http://www.macs.hw.ac.uk/~mjc/wp-mjc...xample_7_2.cpp
(you can immediatly destroy the stdafx.h include because it's seem me very too platform dependant and I don't see
why is it here ...) 

You can easily add variables for to handling the rotation and scaling speeds using rotation/scaling variables coupled
with a detection of mouse movements 
(for example, left/right for the rotation and bottom/top for scaling)
=> this is typically an excellent exercice for to begin with the OpenGL development 


Here an working example :

// Example_7_2.cpp : Using Rotation with Vertex Arrays
//
// Author  : E. Angel, Interactive Computer Graphics
//           A Top-Down Approach with OpenGL, Third Edition
//           Addison-Wesley Longman, 2003
// Version : 1.1 - Commenting changed to match other examples style
//
// Using Vertex Arrays
//
// Program behaviour:
// Left Mouse Button (LMB) spins the cube on its X-Axis
// Right Mouse Button (RMB) spins the cube on its Y-Axis
// Middle Mouse Button (MMB) spins the cube on its Z-Axis
//
// Callback commentary sent to normal command window.
//
// Last tested in Visual C++ 2010 Express

// YLP 01/05/2013 : add a dynamic rotation and scaling (+ comment the stdafx.h include for to be more cross-platform compliant)
// mouse left/right movments during mouse button down :  handle the rotation speed
// mouse top/bottom movments durinf mouse button down :  handle the general scaling of the cube
// tested on Linux

// #include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <GL/glut.h>

//======================================================
// GLOBAL VARIABLES
//======================================================

GLfloat vertices[] =
{-1.0,-1.0,-1.0,
1.0,-1.0,-1.0,
1.0,1.0,-1.0,
-1.0,1.0,-1.0,
-1.0,-1.0,1.0,
1.0,-1.0,1.0,
1.0,1.0,1.0,
-1.0,1.0,1.0};

GLfloat colors[] =
{0.0,0.0,0.0,
1.0,0.0,0.0,
1.0,1.0,0.0,
0.0,1.0,0.0,
0.0,0.0,1.0,
1.0,0.0,1.0,
1.0,1.0,1.0,
0.0,1.0,1.0};

// define cube faces
// each set of 4 indices indicates a different face
GLubyte cubeIndices[]=
{0,3,2,1,
2,3,7,6,
0,4,7,3,
1,2,6,5,
4,5,6,7,
0,1,5,4};

static GLfloat theta[] = {0.0, 0.0, 0.0}; // Rotation (X,Y,Z)
static GLint axis = 2; // Changed by the Mouse Callback Routine

// YLP 01/05/2013 : add scaling and dynamics rotations speed
static int lastx = 0, lasty = 0;
static GLfloat rotate_speed = 0.5f;
static GLfloat  scaling = 1.0f;

//======================================================
// MOUSE CALLBACK ROUTINE
//======================================================
void mouseCallBack(int btn, int state, int x, int y)
{

// Changes the rotation axis depending on the mouse button pressed.
if ( state == GLUT_DOWN )
{
if( btn == GLUT_LEFT_BUTTON ) axis = 0;
if( btn == GLUT_MIDDLE_BUTTON ) axis = 1;
if( btn == GLUT_RIGHT_BUTTON) axis = 2;
}
}

// YLP 01/05/2013 : add dynamics rotation and scaling speed
void motionCallBack(int x, int y)
{
int movx, movy;

movx = lastx - x;
movy = lasty - y;

if ( abs(movx) < 10 ){ rotate_speed += (float)(movx) / 50.0f; }
if ( abs(movy) < 10 ){ scaling  += (float)(movy) / 100.0f;  }

if ( scaling < 00.1f) scaling = 0.1f;
if ( scaling > 10.0f) scaling = 10.0f;

lastx = x;
lasty = y;
}

//======================================================
// IDLE CALLBACK ROUTINE
//======================================================
// YLP 01/05/2013 : add dynamic rotation speed + scaling speed/limits
void idleCallBack()
{
// Spins the cube around the set axis.
theta[axis] += rotate_speed;

while( theta[axis] > 360.0 ) theta[axis] -= 360.0;
while( theta[axis] < 360.0 ) theta[axis] += 360.0;

glutPostRedisplay();
}

//======================================================
// WINDOW RESHAPE ROUTINE
//======================================================
void displayReshape(int w, int h)
{
// If the display is re-sized in any way, the cube is redrawn
// so that it fits the display properly. Try it!

glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho(-4.0, 4.0, -3.0 * (GLfloat) h / (GLfloat) w,
5.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
else
glOrtho(-4.0 * (GLfloat) w / (GLfloat) h,
4.0 * (GLfloat) w / (GLfloat) h, -3.0, 5.0, -10.0, 10.0);
glMatrixMode(GL_MODELVIEW);
}

//======================================================
// DISPLAY CALL BACK ROUTINE
//======================================================
void displayCallBack()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glLoadIdentity();
gluLookAt(1.0,1.0,1.0,0.0,0.0,0.0,0.0,1.0,0.0);
glTranslatef(0.0, 1.0, 0.0);
glRotatef(theta[0], 1.0, 0.0, 0.0);
glRotatef(theta[1], 0.0, 1.0, 0.0);
glRotatef(theta[2], 0.0, 0.0, 1.0);
glScalef(scaling, scaling, scaling);

// Now draw the cube
glColorPointer(3,GL_FLOAT, 0, colors);
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_BYTE, cubeIndices);

glutSwapBuffers();
}

//======================================================
// MAIN PROGRAM
//======================================================
int main(int argc, char** argv)
{
// Allow cmd line arguments to be passed to the glut
glutInit(&argc, argv);

// Create and name window
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH); // Need both double buffering and z buffer
glutInitWindowSize(500, 500);
glutCreateWindow("Example 7.2 - Vertex Arrays");

// Add Display & Mouse CallBacks
glutReshapeFunc(displayReshape);
glutD
4000
isplayFunc(displayCallBack);
glutIdleFunc(idleCallBack);
glutMouseFunc(mouseCallBack);
glutMotionFunc(motionCallBack);

glShadeModel(GL_FLAT); //use one colour per face
glEnable(GL_DEPTH_TEST); /* Enable hidden--surface--removal */
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3,GL_FLOAT, 0, colors);
glClearColor(0.0,0.0,0.0,1.0);
glColor3f(0.0,0.0,0.0);

// Print information about the application in the command console
printf("Cube Rotation & Vertex Array Example\nChange Axis of Rotation by pressing Left, Right or Middle Mouse Buttons\n\n");

//Enter infinite loop calling 'displayCallBack'
glutMainLoop();

return 0;
}

zoom-in、zoom-out与图形放大、图形缩小的差别

许多人不知道zoom-in、zoom-out的确切意义，以为zoom-in就是图形放大、zoom-out就是图形缩小。其实，它们是有差别的。下面我来解释一下其中差别。

 

     zoom的意思是改变视距。zoom-in是将视距缩小，相当于离开事物近一点距离去观察事物，故看到物体确实会变大；zoom-out是将视距放大，即离开事物远一点去观察事物，所以事物看到确实会缩小。从这个角度来看，说zoom-in就是图形放大、zoom-out就是图形缩小也没有错。如果你用百度或Google翻译一下zoom in 或zoom out的中文，结果也会得到这样的解释。

      但另一方面，图形放大不一定要改变人对物体观察距离才能形成，将摄影所得底片或者你以前保存的小照片拿到照相馆去，他们也能将底片或旧照片上的任何形像放大。

     计算机中讲的图形放大就包含两种意义下的放大，而且通常指的是后一种意义的放大。

     照片是一个平面的东西，图形放大或缩小都是对这平面图形本身尺寸的改变，和物体已没有关系。图形放大和缩小是靠计算机软件来实现的，没有计算机，图形是不会放大缩小的。在图形放大或缩小是，人与图形的距离不发生关系。从几何学观点来看，图形放大就是一个相似变换，放大前后的两个图形是完全相似的。而zoom
in 或zoom out则不同，这是一个透视变换：如果物体本身是一平面图，则zoomIn的效果也会和放大完全一样，但如果物体是三维的，或者有背景存在，情况就会不同：在改变同一视距的情况下，在被观察到的不同物体中，距离近的大小相对变化大，距离远的物体相对变化小。下面有几种现成的图片可以说明一些问题。这里用到zoom，也用到缩放。



1 一张C60分子图形，所有原子一样大，但距离远的原子画得要小一点，因人观察它们时所撑视角小了



2 zoom in同时适当输小 后，近的原子变大明显，远的变化也变大，但不明显，因变化的距离比例不大，且为了维持整个分子的尺寸不变，所有原子要输小，这样距离远原子反而的显得小了



3 再 zoom in和整个分子适当缩小 ，近的原子变更大，为了保持整个分子不变，远的原子反而输小更多，明显失真了






4 如果只有缩放，那么就如上所示，各部分图形都有相同大小的变化率