Page 164 - DCAP313_LAB_ON_COMPUTER_GRAPHICS

Lab on Computer Graphics

Notes Source code for Shearing Algorithm C Programming
#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<graphics.h>
void shearing ()
{
int sh;
float xn 1 , yn 1 , xn 2 , yn 2 ;
printf (“Enter the value of Shearing”);
scanf(“%d”,&sh);
cleardevice();
outtextxy(500,100, “SHEARING”);
xn 1 =x 1 +sh*y 1 ;
yn 1 =y 1 ;
xn 2 =x 2 +sh*y 2 ;
yn 2 =y 2 ;
line(x 1 ,y 1 ,x 2 ,y 2 );
line(xn 1 ,yn 1 ,xn 2 ,yn 2 );
getch();
}

10.2 Rotation

Rotation of a planar body is the movement when points of the body travel in circular trajectories
around a fixed point called the centre of rotation. For a three-dimensional body, the rotation
is around an axis it quantity to rotation in each plane perpendicular to the axis around the
intersection of the plane and the axis.
An example of rotation of a planar figure around a point is the movement of the propeller of
an aircraft. A door attached to the wall by two or more hinges rotates around the axis going
through the hinges.
If the axis of rotation is within the body, the body is said to rotate upon itself, or spin. Among
such rotations, the simplest case is that of constant angular frequency.

A rotation is a rigid body movement which keeps a point fixed; unlike a translation. This definition
is applicable both for rotations in a plane (two dimensions) and in space (three dimensions).
It turns out that a rotation in the three-dimensional space keeps fixed not just a single point,
but rather an entire line; that is to say, any rotation in the three dimensional space is a rotation
around an axis.
If one does a rotation around a point (axis), followed by another rotation around the same
point (axis), the total result is yet another rotation. The reverse (inverse) of a rotation is also
a rotation. It follows that the rotations around a point or axis form a group. If however one
performs rotation around a point (axis) followed by rotation around another point (axis), the
overall movement may not be a rotation anymore.

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