GLFW(OpenGL FrameWork) tutorial 3:Transformation:Translation,Scaling and Rotation.

If you are beginner to OpenGL FrameWork (GLFW) visit my previous tutorial lesson Here so that you can understand in details.Translation ,Scaling and Rotation of object is so easy because OpenGL provide these command to us we don’t have to write our own  Transformation matrix.

Translation command:

Translation is movement along any of the three axis in a 3D scene, for example, moving something the left is a translation on the X axis if you are looking straight on.
Command:
glTranslatef( xValue, yValue, zValue );
e.g:
glTranslate(5.0, 0.0, 0.0);
This translate the scene five unit along positive x-axis. One things you must remember ,all the scene drawn below this command will be translated.
So,if you want to translate only one object then you have to restore the transformation. Restore can be done by putting drawing scene and translation command between glPushMatrix() and glPopMatrix() .

Rotation command:

Turning  the object with respect to any axis is called rotation, and is measured by the number of degrees (or radians) .For example if you have turned from your starting position along any three axis in a 3D scene. With the three main axis being the X, Y and Z axis. You can also rotate the object with respect to any arbitary axis.
Command:
glRotatef(angleRotatation, xValue, yValue, zValue);
angleRotation can be +ve for anticlockwise rotation and -ve for clockwise rotation.
x,y,z vaue are the axis of rotation.

Scaling Command:

Scaling means increasing/decreasing size of object by a given factor. If scaling factor is more than one then size increases and for factor less than more decreases the size.
Command:
glScalef(xValue,yValue,zValue);
Now,lets take a look to the code below:

//include header file for glfw library so that we can use OpenGL

#include <GL/glfw.h>

#include <stdlib.h>  //needed for exit function

#include <iostream>

using namespace std;

//Initializes 3D rendering

void initializeRendering()

{

    glfwInit();

    //Makes 3D drawing work when something is in front of something else

    glEnable(GL_DEPTH_TEST);

}

//Called when a key is pressed

void GLFWCALL handleKeypress(int key,int press) //The key that was pressed

{

    switch (key) {

        case GLFW_KEY_ESC: //Escape key

            exit(0); //Exit the program

    }

}

//Called when the window is resized

void GLFWCALL handleResize(int width,int height)

{

    //Tell OpenGL how to convert from coordinates to pixel values

    glViewport( 0, 0, width, height );

    glMatrixMode( GL_PROJECTION ); //Switch to setting the camera perspective

    //Set the camera perspective

    glLoadIdentity(); //reset the camera

    gluPerspective( 45.0f,                      //camera angle

                (GLfloat)width/(GLfloat)height, //The width to height ratio

                 1.0f,                          //The near z clipping coordinate

                100.0f );                       //The far z clipping coordinate

}

void display()

{

    glClearColor( 0.0f, 0.0f, 0.0f, 0.0f ); //clear background screen to black

    //Clear information from last draw

    glClear( GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective

    glLoadIdentity(); //Reset the drawing perspective

    glTranslatef(0.0f,0.0f,-35.0f); //Translate whole scene to -ve z-axis by -35 unit

    glPushMatrix();

    glTranslatef(-2.0f,0.0f,0.0f); //Translate only Rectangle

    glBegin(GL_POLYGON); //Begin quadrilateral coordinates

    //Trapezoid

    glVertex3f(-2.0f,0.0f,5.0f);

    glVertex3f(-5.0f,0.0f,5.0f);

    glVertex3f(-5.0f,5.0f,5.0f);

    glVertex3f(-2.0f,5.0f,5.0f);

    glEnd(); //End quadrilateral coordinates

    glPopMatrix();

    glPushMatrix();

    glTranslatef(2.0f,0.0f,0.0f); //Translate it

    glScalef(1.5f,1.5f,1.5f); //scale the triangle all side by factor 1.5 unit

    glBegin(GL_TRIANGLES); //Begin triangle coordinates

    glVertex3f(3.0f,0.0f,0.0f);

    glVertex3f(0.0f,-3.0f,0.0f);

    glVertex3f(6.0f,-3.0f,0.0f);

    glEnd(); //End triangle coordinates

    glPopMatrix();

    glPushMatrix();

    glTranslatef(0.0f,3.0f,0.0f); //translate it

    glRotatef(30,0.0f,0.0f,1.0f); //rotate the pentagon by 30 degree anti-clockwise

    glBegin(GL_POLYGON);

    glVertex3f(1.0f,0.0f,0.0f);

    glVertex3f(5.0f,0.0f,0.0f);

    glVertex3f(5.0f,4.0f,0.0f);

    glVertex3f(3.0f,6.0f,0.0f);

    glVertex3f(1.0f,4.0f,0.0f);

    glEnd();

    glPopMatrix();

    glfwSwapBuffers();

}

int main()

{

   // int     width, height;

    //int     frame = 0;

    bool    running = true;

    initializeRendering();

    if( !glfwOpenWindow( 800, // width of window

                         800, //height of window

                          0,  //redbits

                          0,  //greenbits

                          0,  //bluebits

                          0,  //alphabits

                          0,  //depthbits

                          0, //stencilbits

                          GLFW_WINDOW ) //mode

        ) //return false if window is not created

    {

        glfwTerminate(); //terminating glfw window

        return 0;

    }

    glfwSetWindowTitle("codeincodeblock.blogspot.com - Transformation");

    glfwSetWindowSizeCallback(handleResize); //callback function of GLFW to handle window resize

    glfwSetKeyCallback(handleKeypress); //callback function to handle keypress

    while(running) // infinite loop to draw object again and again

    {              // because once object is draw then window is terminated

        display();

        running = glfwGetWindowParam( GLFW_OPENED ); //when glfw window is opened then it return true

                                                     //if closed then return false

    }

    return 0;

}

You can also download the project fiel form here Download