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Category: Γ' Εξάμηνο: OpenGL Published: Tuesday, 02 February 2016 Written by Γεώργιος Παπαλουκάς

OpenGL: Μάθημα 5ο - Κίνηση / Animation #2

Το animation είναι δυνατό να επιτευχθεί με χρήση χρονιστή (timer) πέρα από τη χρήση του idle event, περίπτωση που εξετάστηκε ήδη σε προηγούμενο μάθημα. Ο κώδικας που ακολουθεί είναι παραλλαγή του κώδικα του 4ου μαθήματος (πηγή https://www.ntu.edu.sg/home/ehchua/programming/opengl/CG_Examples.html).

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/*
 * OGL02Animation.cpp: 3D Shapes with animation
 */
#include <windows.h>  // for MS Windows
#include <GL/glut.h>  // GLUT, include glu.h and gl.h
 
/* Global variables */
char title[] = "3D Shapes with animation";
GLfloat anglePyramid = 0.0f; // Rotational angle for pyramid [NEW]

GLfloat angleCube = 0.0f;   // Rotational angle for cube [NEW]

int refreshMills = 15;      // refresh interval in milliseconds [NEW]
 
/* Initialize OpenGL Graphics */
void initGL() {
   glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set background color to black and opaque
   glClearDepth(1.0f);                   // Set background depth to farthest
   glEnable(GL_DEPTH_TEST);   // Enable depth testing for z-culling
   glDepthFunc(GL_LEQUAL);    // Set the type of depth-test
   glShadeModel(GL_SMOOTH);   // Enable smooth shading
   glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);  // Nice perspective corrections
}
 
/* Handler for window-repaint event. Called back when the window first appears and
   whenever the window needs to be re-painted. */
void display() {
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear color and depth buffers
   glMatrixMode(GL_MODELVIEW);     // To operate on model-view matrix
 
   // Render a color-cube consisting of 6 quads with different colors
   glLoadIdentity();                 // Reset the model-view matrix
   glTranslatef(1.5f, 0.0f, -7.0f);  // Move right and into the screen
   glRotatef(angleCube, 1.0f, 1.0f, 1.0f);  // Rotate about (1,1,1)-axis [NEW]
 
   glBegin(GL_QUADS);                // Begin drawing the color cube with 6 quads
      // Top face (y = 1.0f)
      // Define vertices in counter-clockwise (CCW) order with normal pointing out
      glColor3f(0.0f, 1.0f, 0.0f);     // Green
      glVertex3f( 1.0f, 1.0f, -1.0f);
      glVertex3f(-1.0f, 1.0f, -1.0f);
      glVertex3f(-1.0f, 1.0f,  1.0f);
      glVertex3f( 1.0f, 1.0f,  1.0f);
 
      // Bottom face (y = -1.0f)
      glColor3f(1.0f, 0.5f, 0.0f);     // Orange
      glVertex3f( 1.0f, -1.0f,  1.0f);
      glVertex3f(-1.0f, -1.0f,  1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f( 1.0f, -1.0f, -1.0f);
 
      // Front face  (z = 1.0f)
      glColor3f(1.0f, 0.0f, 0.0f);     // Red
      glVertex3f( 1.0f,  1.0f, 1.0f);
      glVertex3f(-1.0f,  1.0f, 1.0f);
      glVertex3f(-1.0f, -1.0f, 1.0f);
      glVertex3f( 1.0f, -1.0f, 1.0f);
 
      // Back face (z = -1.0f)
      glColor3f(1.0f, 1.0f, 0.0f);     // Yellow
      glVertex3f( 1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f,  1.0f, -1.0f);
      glVertex3f( 1.0f,  1.0f, -1.0f);
 
      // Left face (x = -1.0f)
      glColor3f(0.0f, 0.0f, 1.0f);     // Blue
      glVertex3f(-1.0f,  1.0f,  1.0f);
      glVertex3f(-1.0f,  1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f, -1.0f);
      glVertex3f(-1.0f, -1.0f,  1.0f);
 
      // Right face (x = 1.0f)
      glColor3f(1.0f, 0.0f, 1.0f);     // Magenta
      glVertex3f(1.0f,  1.0f, -1.0f);
      glVertex3f(1.0f,  1.0f,  1.0f);
      glVertex3f(1.0f, -1.0f,  1.0f);
      glVertex3f(1.0f, -1.0f, -1.0f);
   glEnd();  // End of drawing color-cube
 
   // Render a pyramid consists of 4 triangles
   glLoadIdentity();                  // Reset the model-view matrix
   glTranslatef(-1.5f, 0.0f, -6.0f);  // Move left and into the screen
   glRotatef(anglePyramid, 1.0f, 1.0f, 0.0f);  // Rotate about the (1,1,0)-axis [NEW]
 
   glBegin(GL_TRIANGLES);           // Begin drawing the pyramid with 4 triangles
      // Front
      glColor3f(1.0f, 0.0f, 0.0f);     // Red
      glVertex3f( 0.0f, 1.0f, 0.0f);
      glColor3f(0.0f, 1.0f, 0.0f);     // Green
      glVertex3f(-1.0f, -1.0f, 1.0f);
      glColor3f(0.0f, 0.0f, 1.0f);     // Blue
      glVertex3f(1.0f, -1.0f, 1.0f);
 
      // Right
      glColor3f(1.0f, 0.0f, 0.0f);     // Red
      glVertex3f(0.0f, 1.0f, 0.0f);
      glColor3f(0.0f, 0.0f, 1.0f);     // Blue
      glVertex3f(1.0f, -1.0f, 1.0f);
      glColor3f(0.0f, 1.0f, 0.0f);     // Green
      glVertex3f(1.0f, -1.0f, -1.0f);
 
      // Back
      glColor3f(1.0f, 0.0f, 0.0f);     // Red
      glVertex3f(0.0f, 1.0f, 0.0f);
      glColor3f(0.0f, 1.0f, 0.0f);     // Green
      glVertex3f(1.0f, -1.0f, -1.0f);
      glColor3f(0.0f, 0.0f, 1.0f);     // Blue
      glVertex3f(-1.0f, -1.0f, -1.0f);
 
      // Left
      glColor3f(1.0f,0.0f,0.0f);       // Red
      glVertex3f( 0.0f, 1.0f, 0.0f);
      glColor3f(0.0f,0.0f,1.0f);       // Blue
      glVertex3f(-1.0f,-1.0f,-1.0f);
      glColor3f(0.0f,1.0f,0.0f);       // Green
      glVertex3f(-1.0f,-1.0f, 1.0f);
   glEnd();   // Done drawing the pyramid
 
   glutSwapBuffers();  // Swap the front and back frame buffers (double buffering)
 
   // Update the rotational angle after each refresh [NEW]

   anglePyramid += 0.2f;

   angleCube -= 0.15f;
}
 
/* Called back when timer expired [NEW] */

void timer(int value) {

   glutPostRedisplay();      // Post re-paint request to activate display()

   glutTimerFunc(refreshMills, timer, 0); // next timer call milliseconds later

}
 
/* Handler for window re-size event. Called back when the window first appears and
   whenever the window is re-sized with its new width and height */

void reshape(GLsizei width, GLsizei height) {  // GLsizei for non-negative integer
   // Compute aspect ratio of the new window
   if (height == 0) height = 1;                // To prevent divide by 0
   GLfloat aspect = (GLfloat)width / (GLfloat)height;
 
   // Set the viewport to cover the new window
   glViewport(0, 0, width, height);
 
   // Set the aspect ratio of the clipping volume to match the viewport
   glMatrixMode(GL_PROJECTION);  // To operate on the Projection matrix
   glLoadIdentity();             // Reset
   // Enable perspective projection with fovy, aspect, zNear and zFar
   gluPerspective(45.0f, aspect, 0.1f, 100.0f);
}
 
/* Main function: GLUT runs as a console application starting at main() */
int main(int argc, char** argv) {
   glutInit(&argc, argv);            // Initialize GLUT
   glutInitDisplayMode(GLUT_DOUBLE); // Enable double buffered mode
   glutInitWindowSize(640, 480);   // Set the window's initial width & height
   glutInitWindowPosition(50, 50); // Position the window's initial top-left corner
   glutCreateWindow(title);          // Create window with the given title
   glutDisplayFunc(display);       // Register callback handler for window re-paint event
   glutReshapeFunc(reshape);       // Register callback handler for window re-size event
   initGL();                       // Our own OpenGL initialization
   glutTimerFunc(0, timer, 0);     // First timer call immediately [NEW]
   glutMainLoop();                 // Enter the infinite event-processing loop
   return 0;
}

 Η λογική του animation (περιστροφή του κύβου και της πυραμίδας) είναι ο περιοδικός επανασχεδιασμός των αντικειμένων - ελαφρώς "παραλλαγμένων" - στην ωφέλιμη περιοχή του παραθύρου.

Η περιστροφή γίνεται πάντα γύρω από έναν άξονα κατά μία γωνία. Η περιστροφή επιτυγχάνεται με χρήση της εντολής glRotatef.

 

 

Ασκήσεις εμπέδωσης

Παρακαλώ πατήστε εδώ προκειμένου να εξασκηθείτε επεκτείνοντας το πρόγραμμα Animation#2.

 

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