Computer Graphics 5

1
Computer Graphics 5

• Lee Byung-Gook

2
3D Elementary Shapes

• The glut library contains several functions for
  drawing basic 3D primitives. These are listed
  below. All of the following objects are centered
  at the origin
• glutWireCube(GLdouble size)
• glutSolidCube(GLdouble size)
• glutWireSphere(GLdouble radius, GLint nSlices,
  GLint nStacks)
• glutSolidSphere(GLdouble radius, GLint nSlices,
  GLint nStacks)

3
glutWireSphere

• This approximates a sphere with a set of
  polygons. The number of polygons determines the
  "niceness" of the approximation. nSlices is the
  number of subdivisions around the z-axis. nStacks
  is the number of bands along the z axis.
• Large values for nSlices and nStacks produce more
  accurate representations (at the cost of slower
  graphics).
• Small values for nSlices and nStacks produce
  poorer representations (with the benefit of
  faster graphics).

4
3D Elementary Shapes

• glutWireTetrahedron() // 4 faced pyramid
• glutSolidTetrahedron()
• glutWireOctahedron() // 8 faced solid
• glutSolidOctahedron()
• glutWireDodecahedron() // 12 faced solid
• glutSolidDodecahedron()
• glutWireIcosahedron() // 20 faced solid
• glutSolidIcosahedron()

5
3D Elementary Shapes

• glutWireTorus(GLdouble innerRadius, GLdouble
  outerRadius, GLint nSlices, GLint rings)
• glutSolidTorus(GLdouble innerRadius, GLdouble
  outerRadius, GLint nSlices, GLint rings)
• glutWireTeapot(GLdouble size)
• glutSolidTeapot(GLdouble size)
• glutWireCone(GLdouble baseRadius, GLdouble
  height, GLint nSlices, GLint nStacks)
• glutSolidCone(GLdouble baseRadius, GLdouble
  height, GLint nSlices, GLint nStacks)

6
lab07.cpp
include ltmath.hgt include ltstdio.hgt include
ltstdlib.hgt include ltGL/glut.hgt GLint N4 GLint
mouseX 0 GLint mouseY 0 GLint mouseState
0 GLint mouseButton 0 GLint shape1,
model2 GLfloat size2.0 GLfloat xTheta0.,
yTheta0., zTheta0., thetaDelta.125 GLfloat
scale1.0, scaleDelta1.01 void
myAxis(void) int i glColor3f(0.98, .04,
.70) glBegin(GL_LINES)
for(i0 iltN i) glVertex2f(-size2.0isi
ze/N, -size) glVertex2f(-size2.0isize/N,
size) glVertex2f(-size, -size2.0isize/N)
glVertex2f(size, -size2.0isize/N) glEnd()
void myDraw(void) glColor3f(.98, .625,
.12) if(model1) glutWireCube(1.0) else
if(model2) glutSolidCube(1.0) else
if(model3) glutWireSphere(1.0, 10, 10) else
if(model4) glutSolidSphere(1.0, 10, 10) else
if(model5) glutWireTeapot(1.0) else
if(model6) glutSolidTeapot(1.0)
7
lab07.cpp
void myDisplay(void) static int i0 glClear(G
L_COLOR_BUFFER_BIT) glLoadIdentity() glRotatef
(xTheta, 1.0, 0.0, 0.0) glRotatef(yTheta, 0.0,
1.0, 0.0) glRotatef(zTheta, 0.0, 0.0,
1.0) glScalef(scale, scale, scale) myDraw()
glFlush() glutSwapBuffers() void
myReshape(int width, int height) glClearColor
(.75, .75, .75, 0.0) glViewport(0,0,width,height
) glMatrixMode(GL_PROJECTION) glLoadIdentity()
glOrtho(-size, size, -size, size, -size,
size) glMatrixMode(GL_MODELVIEW)
void glutMouse(int btn, int state, int x, int
y) if(btnGLUT_LEFT_BUTTON state
GLUT_DOWN) mouseStatestate mouseButtonbt
n mouseXx mouseYy else
if(btnGLUT_LEFT_BUTTON state GLUT_UP)
mouseState-1 else if(btnGLUT_MIDDLE_BU
TTON state GLUT_DOWN) mouseStatestat
e mouseButtonbtn mouseXx mouseYy
8
lab07.cpp
else if(btnGLUT_MIDDLE_BUTTON state
GLUT_UP) mouseState-1 else
return glutPostRedisplay() void
glutMotion(int x, int y) if(mouseButton
GLUT_LEFT_BUTTON mouseState GLUT_DOWN)
yTheta - (mouseX - x)/10. xTheta -
(mouseY - y)/10. else if(mouseButton
GLUT_MIDDLE_BUTTON mouseState GLUT_DOWN)
if(mouseY!y) scale scale
pow(scaleDelta, (mouseY - y)/10.) else
return
mouseX x mouseY y glutPostRedisplay()
void myMenu(int id) if(id 7)
exit(1) else model id glutPostRedisplay()
9
lab07.cpp
void main(int argc, char argv) int shape_subm
enu glutInit(argc,argv) glutInitDisplayMode
(GLUT_DOUBLE GLUT_RGB) glutInitWindowSize(500,
500) glutInitWindowPosition(0,0) glutCreateWin
dow("lab07") glutReshapeFunc(myReshape) glutDi
splayFunc(myDisplay) glutMouseFunc(glutMouse)
glutMotionFunc(glutMotion) glutCreateMenu(myMen
u) glutAddMenuEntry("WireCube",
1) glutAddMenuEntry("SolidCube",
2) glutAddMenuEntry("WireSphere",
3) glutAddMenuEntry("SolidSphere",
4) glutAddMenuEntry("WireTeapot",
5) glutAddMenuEntry("SolidTeapot",
6) glutAddMenuEntry("Quit", 7) glutAttachMenu(
GLUT_RIGHT_BUTTON) glutMainLoop()
10
glutCreateMenu

• glutCreateMenu creates a new pop-up menu.
• int glutCreateMenu(void (func)(int value))
• Parameters
• func The callback function for the menu that is
  called when a menu entry from the menu is
  selected.
• The value passed to the callback is determined
  by the value for the selected menu entry.

11
glutAddMenuEntry

• glutAddMenuEntry adds a menu entry to the bottom
  of the current menu.
• void glutAddMenuEntry(char name, int value)
• Parameters
• name ASCII character string to display in the
  menu entry.
• value Value to return to the menus callback
  function if the menu entry is selected.

12
glutAttachMenu

• glutAttachMenu attaches a mouse button for the
  current window to the identifier of the current
  menu
• void glutAttachMenu(int button)
• Parameters
• button The button to attach a menu

13
Projection, ModelView matrix

• There are three different 4x4 matrices used by
  OpenGL to produce an image.
• Projection matrix - used to "project" a 3D image
  onto a 2D plane to create an image
• ModelView matrix - used to transform objects and
  the camera to create the desired scene and view.
• Commands like glTranslate, glRotate, and glScale
  modify the active matrix. It is the programmer's
  responsibility to make sure the appropriate
  matrix is "active." The active matrix is
  determined by calls to glMatrixMode().

14
glMatrixMode

• The glMatrixMode function specifies which matrix
  is the current matrix.
• void glMatrixMode( GLenum mode )
• Parameters
• mode The matrix stack that is the target for
  subsequent matrix operations. The mode parameter
  can assume one of three values
• GL_MODELVIEW Applies subsequent matrix
  operations to the modelview matrix stack.
• GL_PROJECTION Applies subsequent matrix
  operations to the projection matrix stack.
• GL_TEXTURE Applies subsequent matrix
  operations to the texture matrix stack.

15
OpenGL transformation functions

• OpenGL maintains a 4x4 transformation matrix that
  is multiplied by every (x,y,z) value sent to
  glVertex().This is sometimes referred to as the
  CT (current transformation, active matrix).
• The CT can be modified by the following
  functions
• glLoadIdentity()
• glTranslatefd(dx, dy, dz)
• glScalefd(sx, sy, sz)
• glRotatefd(angleInDegrees, axisXvalue,
  axisYvalue, axisZvalue)

16
Specifics

• The glLoadIdentity() function is unique. It
  replaces the CT with an identity matrix. This has
  the effect of starting transformations "from
  unity".
• The arguments to these functions can be float or
  double data types. The last letter of the
  function name determines the data type of the
  arguments.
• For example
• glTranslatef(3.0, 4.0, 1.2) // floating point
  data
• glTranslated(3.0, 4.0, 1.2) // double precision
  data

17
Specifics

• To translate along one axis while leaving the
  other axis values unchanged, use a value of zero
  for the unaffected axes.
• For example, the following function call moves
  along the Y axis 6 units glTranslatef(0.0, 6.0,
  0.0)
• To scale along one axis while leaving the other
  axis values unchanged, use a value of one for the
  unaffected axes.
• For example, the following call scales only
  along the Z axis by a factor of 3 glScalef(1.0,
  1.0, 3.0)

18
Specifics

• To rotate about one of the coordinate system
  axes, specify the appropriate vector.
• For example
• glRotatef(20.0, 1.0, 0.0, 0.0) // rotates about
  the X axis
• glRotatef(20.0, 0.0, 1.0, 0.0) // rotates about
  the Y axis
• glRotatef(20.0, 0.0, 0.0, 1.0) // rotates about
  the Z axis

19
Specifics

• For the glTranslate, glRotate, and glScale
  functions, each builds a 4x4 transformation
  matrix using the supplied arguments and then
  multiplies it times the CT (current transform).
  For example, the glTranslatef function might look
  something like the following
• void glTranslatef(float dx, float dy, float dz)
  
• GLfloat m44
• 1.0, 0.0, 0.0, dx ,
• 0.0, 1.0, 0.0, dy ,
• 0.0, 0.0, 1.0, dz ,
• 0.0, 0.0, 0.0, 1.0
• CT CTm // pseudocode

20
Facts about transformations

• Given a sequence of elementary transformations
  that together form a single complex
  transformation, if you change the order of the
  elementary transformations, you get a different
  complex transformation
• There is typically more than one sequence of
  transformations that will produce the same
  effect, but often one sequence is easier to
  create than the others.
• The multiplication of the matrices is always
  (CTm), not (mCT), so the order of the function
  calls must be in reverse order from the
  "conceptual" ordering of the transformations.

21
Specifics

• If you want to
• translate a point by (-2, 5, 0),
• then rotate it by 20 degrees about the Z axis,
• then scale it by a factor of 2 along the X axis,
  
• the function calls would be
•   glLoadIdentity() // always start with the
  identity matrix
• glScalef(2.0, 1.0, 1.0) // Conceptually, this
  happens 3rd
• glRotatef(20.0, 0.0, 0.0, 1.0) // Conceptually,
  this happens 2nd
• glTranslatef(-2.0, 5.0, 0.0) // Conceptually,
  this happens 1st
• drawObject()

22
Specifics

• The transformations caused by glRotate,
  glTranslate, and glScale are applied to the CT
  (current transform). They will accumulate
  continually unless you reset the matrix back to
  the Identity matrix. If you want to start a new
  set of transformations, then call
  glLoadIdentity().
• Example
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity() // start a new sequence of
  transforms
• glTranslatef(-3.0, -4.0, 0.0)
• glRotatef(90.0, 1.0, 0.0, 0.0)
• drawObject1()  
• glLoadIdentity() // start a new sequence of
  transforms
• glTranslatef(4.0, 2.0, 1.0)
• glScalef(2.0, 1.0, 1.0)
• drawObject2()

23
Example 1

• Draw a wall of a building containing 5 arched
  windows, spaced 10 units apart. Assume the arched
  window is defined around the origin and is 4
  units wide

24
Example 1

• 1) reset the matrix
• 2) drawWindow
• 3) translate 8 on X, 5 on Y
• 4) reset the matrix
• 5) drawWindow
• 6) translate 18 on X, 5 on Y
• 7) reset the matrix
• 8) drawWindow
• 9) translate 28 on X, 5 on Y
• 10) reset the matrix
• 11) drawWindow
• 12) translate 38 on X, 5 on Y
• 13) reset the matrix
• 14) drawWindow
• 15) translate 48 on X, 5 on Y

• glLoadIdentity()
• glTranslatef(8.0, 5.0, 0.0)
• drawWindow()
• glLoadIdentity()
• glTranslatef(18.0, 5.0, 0.0)
• drawWindow()
• glLoadIdentity()
• glTranslatef(28.0, 5.0, 0.0)
• drawWindow()
• glLoadIdentity()
• glTranslatef(38.0, 5.0, 0.0)
• drawWindow()
• glLoadIdentity()
• glTranslatef(48.0, 5.0, 0.0)
• drawWindow()

25
Example 1

• 1) reset the matrix
• 2) drawWindow
• 3) translate 10 on X, 0 on Y
• 4) drawWindow
• 5) translate 10 on X, 0 on Y
• 6) drawWindow
• 7) translate 10 on X, 0 on Y
• 8) drawWindow
• 9) translate 10 on X, 0 on Y
• 10) drawWindow
• 11) translate 8 on X, 5 on Y

• glLoadIdentity()
• glTranslatef(8.0, 5.0, 0.0)
• drawWindow()
• glTranslatef(10.0, 0.0, 0.0)
• drawWindow()
• glTranslatef(10.0, 0.0, 0.0)
• drawWindow()
• glTranslatef(10.0, 0.0, 0.0)
• drawWindow()
• glTranslatef(10.0, 0.0, 0.0)
• drawWindow()

26
lab08.cpp
include ltmath.hgt include ltstdio.hgt include
ltstdlib.hgt include ltGL/glut.hgt GLint N12 GLfloa
t size60.0 void myAxis(void) int i glColor3
f(.98, .04, .70) glBegin(GL_LINES) for(i0
iltN i) glVertex2f(-size2.0isize/N,
-size) glVertex2f(-size2.0isize/N,
size) glVertex2f(-size, -size2.0isize/N)
glVertex2f(size, -size2.0isize/N) glEnd()
glColor3f(.25, .25, .25) glBegin(GL_LINES)
glVertex2f(0, -size) glVertex2f(0, size)
glVertex2f(-size, 0) glVertex2f(size,
0) glEnd() void drawWindow(void) glBegin(G
L_POLYGON) glVertex3f(-3., 0.,
0.) glVertex3f(3., 0., 0.) glVertex3f(3., 8.,
0.) glVertex3f(2.954423, 8.520945,
0.) glVertex3f(2.819078, 9.026060,
0.) glVertex3f(2.598076, 9.500000,
0.) glVertex3f(2.298133, 9.928363,
0.) glVertex3f(1.928363, 10.298133,
0.) glVertex3f(1.500000, 10.598076,
0.) glVertex3f(1.026060, 10.819078,
0.) glVertex3f(.520945, 10.954423,
0.) glVertex3f(0.000000, 11.000000,
0.) glVertex3f(-.520945, 10.954423,
0.) glVertex3f(-1.026060, 10.819078,
0.) glVertex3f(-1.500000, 10.598076, 0.)
27
lab08.cpp
glVertex3f(-1.928363, 10.298133,
0.) glVertex3f(-2.298133, 9.928363,
0.) glVertex3f(-2.598076, 9.500000,
0.) glVertex3f(-2.819078, 9.026060,
0.) glVertex3f(-2.954423, 8.520945,
0.) glVertex3f(-3., 8., 0.) glEnd() void
myDisplay(void) glClear(GL_COLOR_BUFFER_BIT)
glLoadIdentity() myAxis() glColor3f(.25,
.25, .12) drawWindow() glColor3f(.98, .625,
.12) for(int j0 jlt5 j)
glLoadIdentity() glTranslatef(810.0j, 5.0,
0.0) drawWindow() glFlush()
glutSwapBuffers() void myReshape(int width,
int height) glClearColor (.75, .75, .75,
0.0) glViewport(0,0,width,height) glMatrixMode
(GL_PROJECTION) glLoadIdentity() glOrtho(-size
, size, -size, size, -size, size) glMatrixMode(G
L_MODELVIEW) void main(int argc, char
argv) glutInit(argc,argv) glutInitDisplayMod
e (GLUT_DOUBLE GLUT_RGB) glutInitWindowSize(50
0,500) glutInitWindowPosition(0,0) glutCreateW
indow("lab08") glutReshapeFunc(myReshape) glut
DisplayFunc(myDisplay) glutMainLoop()
28
Exercise 1

• Compare the difference

• glLoadIdentity()
• glTranslatef(10.0, 0.0, 0.0)
• glRotatef(theta, 0.0, 0.0, 1.0)
• glutWireSphere(1.0, 10, 10)

• glLoadIdentity()
• glRotatef(theta, 0.0, 0.0, 1.0)
• glTranslatef(10.0, 0.0, 0.0)
• glutWireSphere(1.0, 10, 10)

29
Example 2

• Transform the triangle from its current location
  (left) to the new location and orientation shown
  on right.

30
Example 2

• 1) drawTriangle
• 2) rotate 90 degrees about Z
• 2) translate 10 units along Y

• glLoadIdentity()
• glTranslatef(0.0, 10.0, 0.0)
• glRotatef(90.0, 0.0, 0.0, 1.0)
• drawTriangle()

31
Example 2

• 1) drawTriangle
• 2) translate 10 units along X
• 3) rotate 90 degrees about Z

• glLoadIdentity()
• glRotatef(90.0, 0.0, 0.0, 1.0)
• glTranslatef(10.0, 0.0, 0.0)
• drawTriangle()

32
Example 2

• 1) drawTriangle
• 2) rotate -90 degrees about Z
• 3) translate -10 along Y
• 4) rotate 180 degrees about Z

• glLoadIdentity()
• glRotatef(180.0, 0.0, 0.0, 1.0)
• glTranslatef(0.0, -10.0, 0.0)
• glRotatef(-90.0, 0.0, 0.0, 1.0)
• drawTriangle()

33
lab09.cpp
include ltmath.hgt include ltstdio.hgt include
ltstdlib.hgt include ltGL/glut.hgt GLint N6 GLfloa
t size30.0 void myAxis(void) int i glColor
3f(.98, .04, .70) glBegin(GL_LINES) for(i0
iltN i) glVertex2f(-size2.0isize/N,
-size) glVertex2f(-size2.0isize/N,
size) glVertex2f(-size, -size2.0isize/N)
glVertex2f(size, -size2.0isize/N) glEnd()
glColor3f(.25, .25, .25)
glBegin(GL_LINES) glVertex2f(0,
-size) glVertex2f(0, size) glVertex2f(-size,
0) glVertex2f(size, 0) glEnd() void
drawTriangle(void) glBegin(GL_POLYGON) glColo
r3f(.0, .0, 1.0) glVertex3f(-5., -5.,
0.) glColor3f(.0, .0, 1.0) glVertex3f(5.,
-5., 0.) glColor3f(1.0, .0, .0)
glVertex3f(0., 5., 0.) glEnd()
34
lab09.cpp
void myDisplay(void) glClear(GL_COLOR_BUFFER_B
IT) glLoadIdentity() myAxis() glLoadIdentity
() glTranslatef(0.0, 10.0, 0.0) glRotatef(90.0
, 0.0, 0.0, 1.0) drawTriangle() glFlush() gl
utSwapBuffers() void myReshape(int width, int
height) glClearColor (.75, .75, .75,
0.0) glViewport(0,0,width,height) glMatrixMode
(GL_PROJECTION) glLoadIdentity() glOrtho(-size
, size, -size, size, -size, size) glMatrixMode(G
L_MODELVIEW)
void main(int argc, char argv) glutInit(argc
,argv) glutInitDisplayMode (GLUT_DOUBLE
GLUT_RGB) glutInitWindowSize(500,500) glutInit
WindowPosition(0,0) glutCreateWindow("lab09")
glutReshapeFunc(myReshape) glutDisplayFunc(myDis
play) glutMainLoop()
35
Exercise 2

• From lab09
• Find another sequence of transformations that
  will produce the same effect

36
Matrix Stack

• Problem Matrix multiplication is
  computationally expensive.
• The multiplication of two 4x4 matrices requires
  64 multiples and 48 additions
• Solution Avoid duplicate matrix multiplication
  by saving transformations that will be needed
  again.
• A stack is a good way to store a series of
  transformations for later use

37
OpenGL implementation

• OpenGL maintains a stack that can hold a minimum
  of 32 matrices. The matrix at the top of the
  stack is always the CT (Current Transform)
• The following two commands manipulate the matrix
  stack
• glPushMatrix()
• glPopMatrix()

38
OpenGL implementation

• Assuming that the stack is implemented as an
  array, these two functions look like the
  following pseudocode
• // The stack begins with an Identity matrix on
  top
• int stackTop 1
• Matrix4x4 Identity 1, 0, 0, 0,0, 1, 0,
  0,0, 0, 1, 0,0, 0, 0, 1
• Matrix4x4 MatrixStack32 Identity, 0
•  void glPushMatrix(void)
• MatrixStackstackTop MatrixStackstackTop-1
  
• stackTop
•   void glPopMatrix(void)
• stackTop--
•   // The CT (current transform) is always
  MatrixStackstacktop-1

39
Matrix Stack
Statements stack0 stack1
glLoadIdentity() glRotatef(xTheta, 1.0, 0.0, 0.0) glRotatef(yTheta, 0.0, 1.0, 0.0) glRotatef(zTheta, 0.0, 0.0, 1.0) glScalef(scale, scale, scale) glutWireSphere(3.0, 10, 10) glRotatef(theta, 0., 0., 1.) glTranslatef(20., 0., 0.) glutWireSphere(1.0, 10, 10) glPushMatrix() glRotatef(theta, 0., 0., 1.) glTranslatef(5., 0., 0.) glutWireSphere(.5, 10, 10) glPopMatrix() glRotatef(theta, 0., 0., 1.) glTranslatef(-5., 0., 0.) glutWireSphere(.5, 10, 10) M0 I M0 M0Rx, xTheta M0 M0Ry, yTheta M0 M0Rz, zTheta M0 M0Sscale, scale, scale M0 M0 M0Rz, theta M0 M0Tx, 20. M0 M0 M0 M0 M0 M0 M0 M0Rz, theta M0 M0Tx,,5. M0 - - - - - - - - - M1 M0 M1 M1Rz, theta M1 M1Tx,,5. M1 - - - -
40
lab10.cpp
include ltmath.hgt include ltstdio.hgt include
ltstdlib.hgt include ltGL/glut.hgt bool idleFlag
1 GLint N6 GLint mouseX 0 GLint mouseY
0 GLint mouseState 0 GLint mouseButton 0
GLfloat size30.0, theta0.0 GLfloat xTheta0.,
yTheta0., zTheta0., thetaDelta.125 GLfloa
t scale1.0, scaleDelta1.01
void myAxis(void) int i glColor3f(.98, .04,
.70) glutWireCube(size2.0) glBegin(GL_LINES)
for(i0 iltN i) glVertex2f(-size2.0i
size/N, -size) glVertex2f(-size2.0isize/N,
size) glVertex2f(-size, -size2.0isize/N)
glVertex2f(size, -size2.0isize/N) glEnd()
glColor3f(.25, .25, .25) glBegin(GL_LINES)
glVertex2f(0, -size) glVertex2f(0,
size) glVertex2f(-size, 0) glVertex2f(size,
0) glEnd()
41
lab10.cpp
void myDisplay(void) glClear(GL_COLOR_BUFFER_B
IT) glLoadIdentity() glRotatef(xTheta, 1.0,
0.0, 0.0) glRotatef(yTheta, 0.0, 1.0,
0.0) glRotatef(zTheta, 0.0, 0.0,
1.0) glScalef(scale, scale, scale) myAxis()
glColor3f(.98, .625, .12) glutWireSphere(3.0,
10, 10) glRotatef(theta, 0., 0.,
1.) glTranslatef(20., 0., 0.) glutWireSphere(1
.0, 10, 10) glPushMatrix() glRotatef(theta,
0., 0., 1.) glTranslatef(5., 0.,
0.) glutWireSphere(.5, 10, 10) glPopMatrix()
glRotatef(theta, 0., 0., 1.)
glTranslatef(-5., 0., 0.) glutWireSphere(.5,
10, 10) glFlush() glutSwapBuffers() void
myReshape(int width, int height) glClearColor
(.75, .75, .75, 0.0) glViewport(0,0,width,height
) glMatrixMode(GL_PROJECTION) glLoadIdentity()
glOrtho(-size, size, -size, size, -size,
size) glMatrixMode(GL_MODELVIEW) void
myIdle(void) theta0.5 glutPostRedisplay()

42
lab10.cpp
void myMouse(int btn, int state, int x, int
y) if(btnGLUT_LEFT_BUTTON state
GLUT_DOWN) mouseStatestate mouseButtonb
tn mouseXx mouseYy else
if(btnGLUT_LEFT_BUTTON state GLUT_UP)
mouseState-1 else if(btnGLUT_RIGHT_BUT
TON state GLUT_DOWN) mouseStatestate
mouseButtonbtn mouseXx mouseYy
else if(btnGLUT_RIGHT_BUTTON state
GLUT_UP) mouseState-1 else
if(btnGLUT_MIDDLE_BUTTON state
GLUT_DOWN) xThetayThetazTheta0. scale1.
0 else return if(idleFlag
stateGLUT_DOWN) glutIdleFunc(NULL) else
if(idleFlag stateGLUT_UP) glutIdleFunc(myI
dle) glutPostRedisplay()
43
lab10.cpp
void myMotion(int x, int y) if(mouseButton
GLUT_LEFT_BUTTON mouseState GLUT_DOWN)
yTheta - (mouseX - x)/1. xTheta -
(mouseY - y)/1. else if(mouseButton
GLUT_RIGHT_BUTTON mouseState GLUT_DOWN)
if(mouseY!y) scale scale
pow(scaleDelta, (mouseY - y)/1.) else
return mouseX x mouseY y glutPostRedispl
ay() void myKeyboard(unsigned char theKey, int
x, int y) switch (theKey) case ' '
idleFlag!idleFlag
if(idleFlag) glutIdleFunc(myIdle) else
glutIdleFunc(NULL) break case 27
exit(-1) // esc key glutPostRedisplay() vo
id main(int argc, char argv) glutInit(argc,a
rgv) glutInitDisplayMode (GLUT_DOUBLE
GLUT_RGB) glutInitWindowSize(500,500) glutInit
WindowPosition(0,0) glutCreateWindow("lab09")
glutReshapeFunc(myReshape) glutDisplayFunc(myDis
play) glutMouseFunc(myMouse) glutMotionFunc(m
yMotion) glutKeyboardFunc(myKeyboard) glutMain
Loop()
44
Homework 4.

• In two weeks
• Draw a house with more than 2 windows and 2
  doors.
• Rotate the house depend on the mouse movement
  while left mouse button are pressed.