中文XML论坛--openGL中的选择机制

#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <math.h>

#define glRGB(x, y, z) glColor3ub((GLubyte)x, (GLubyte)y, (GLubyte)z)

#define SUN 1
#define MERCURY 2
#define VENUS 3
#define EARTH 4
#define MARS 5

GLfloat fAspect;
int n;
// Lighting values
GLfloat  whiteLight[] = { 0.35f, 0.35f, 0.35f, 1.0f };
GLfloat  sourceLight[] = { 0.65f, 0.65f, 0.65f, 1.0f };
GLfloat  lightPos[] = { 0.0f, 0.0f, 0.0f, 1.0f };

// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Save the matrix state and do the rotations
glMatrixMode(GL_MODELVIEW);
glPushMatrix();

// Translate the whole scene out and into view
glTranslatef(0.0f, 0.0f, -300.0f);

// Initialize the names stack
glInitNames();
glPushName(0);

// Set material color, Yellow
// Sun
glRGB(255, 255, 255);
glLoadName(SUN);
glutSolidSphere(15.0f, 15, 15);

// Draw Mercury
glRGB(128,0,0);
glPushMatrix();
glTranslatef(24.0f, 0.0f, 0.0f);
glLoadName(MERCURY);
glutSolidSphere(2.0f,15,15);
glPopMatrix();

// Draw Venus
glPushMatrix();
glRGB(128,128,255);
glTranslatef(60.0f, 0.0f, 0.0f);
glLoadName(VENUS);
glutSolidSphere(4.0f,15,15);
glPopMatrix();

// Draw the Earth
glPushMatrix();
glRGB(0,0,255);
glTranslatef(100.0f,0.0f,0.0f);
glLoadName(EARTH);
glutSolidSphere(8.0f,15,15);
glPopMatrix();

// Draw Mars
glRGB(255,0,0);
glPushMatrix();
glTranslatef(150.0f, 0.0f, 0.0f);
glLoadName(MARS);
glutSolidSphere(4.0f,15,15);
glPopMatrix();

// Restore the matrix state
glPopMatrix(); // Modelview matrix

glutSwapBuffers();
}

// Present the information on which planet/sun was selected and displayed
void ProcessPlanet(GLuint id)
{
switch(id)
  {
  case SUN:
   MessageBox(NULL,"You clicked on the Sun!","Info",MB_OK | MB_ICONEXCLAMATION);
   break;

  case MERCURY:
   MessageBox(NULL,"You clicked on Mercury!","Info",MB_OK | MB_ICONEXCLAMATION);
   break;

  case VENUS:
   MessageBox(NULL,"You clicked on Venus!","Info",MB_OK | MB_ICONEXCLAMATION);
   break;

  case EARTH:
   MessageBox(NULL,"You clicked on Earth!","Info",MB_OK | MB_ICONEXCLAMATION);
   break;

  case MARS:
   MessageBox(NULL,"You clicked on Mars!","Info",MB_OK | MB_ICONEXCLAMATION);
   break;

  default:
   MessageBox(NULL,"Nothing was clicked on!","Error",MB_OK | MB_ICONEXCLAMATION);
   break;
  }
}

// Process the selection, which is triggered by a right mouse
// click at (xPos, yPos).
#define BUFFER_LENGTH 64

// 重点段

void ProcessSelection(int xPos, int yPos)
{
// Space for selection buffer
GLuint selectBuff[BUFFER_LENGTH];

// Hit counter and viewport storeage
GLint hits, viewport[4];

// Setup selection buffer
glSelectBuffer(BUFFER_LENGTH, selectBuff);

// Get the viewport
glGetIntegerv(GL_VIEWPORT, viewport);

// Switch to projection and save the matrix
glMatrixMode(GL_PROJECTION);
glPushMatrix();

// Change render mode
glRenderMode(GL_SELECT);

// Establish new clipping volume to be unit cube around
// mouse cursor point (xPos, yPos) and extending two pixels
// in the vertical and horzontal direction
glLoadIdentity();
gluPickMatrix(xPos, viewport[3] - yPos, 2,2, viewport);
// Apply perspective matrix
gluPerspective(45.0f, fAspect, 1.0, 425.0);

// Draw the scene
RenderScene();

// Collect the hits
hits = glRenderMode(GL_RENDER);

// If a single hit occured, display the info.
if(hits == 1)
ProcessPlanet(selectBuff[3]);

// Restore the projection matrix
glMatrixMode(GL_PROJECTION);
glPopMatrix();

// Go back to modelview for normal rendering
glMatrixMode(GL_MODELVIEW);

// n=selectBuff[0];
// printfn;

}

// Process the mouse click
void MouseCallback(int button, int state, int x, int y)
{
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
ProcessSelection(x, y);
}

// This function does any needed initialization on the rendering
// context.
void SetupRC()
{
// Light values and coordinates
glEnable(GL_DEPTH_TEST); // Hidden surface removal
glFrontFace(GL_CCW); // Counter clock-wise polygons face out
glEnable(GL_CULL_FACE); // Do not calculate insides

// Enable lighting
glEnable(GL_LIGHTING);

// Setup and enable light 0
glLightModelfv(GL_LIGHT_MODEL_AMBIENT,whiteLight);
glLightfv(GL_LIGHT0,GL_DIFFUSE,sourceLight);
glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
glEnable(GL_LIGHT0);

// Enable color tracking
glEnable(GL_COLOR_MATERIAL);

// Set Material properties to follow glColor values
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

// Black blue background
glClearColor(0.60f, 0.60f, 0.60f, 1.0f );
}

void ChangeSize(int w, int h)
{
// Prevent a divide by zero
if(h == 0)
h = 1;

// Set Viewport to window dimensions
glViewport(0, 0, w, h);

// Calculate aspect ratio of the window
fAspect = (GLfloat)w/(GLfloat)h;

// Set the perspective coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

// Field of view of 45 degrees, near and far planes 1.0 and 425
gluPerspective(45.0f, fAspect, 1.0, 425.0);

// Modelview matrix reset
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(600,300);
glutCreateWindow("Pick a Planet");
glutReshapeFunc(ChangeSize);
glutMouseFunc(MouseCallback);
glutDisplayFunc(RenderScene);
SetupRC();
glutMainLoop();
return 0;
}


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