1. Chapter 3 Viewing

2. Contents Overview: The Camera Analogy
Viewing and Modeling Transformation
Projection Transformation
Viewport Transformation

3. Chapter Objectives View a geometric model in any orientation
Control the location in 3D space
Clip Undesired portions of the model

4. Overview -The Camera Analogy-

5. Overview: The Camera Analogy
Viewing Transformation
Positioning the view volume in the world
Modeling Transformation
Positioning models in the world
Projection Transformation
Determining the shape of the view volume
Viewport Transformation

6. Method for Transformation - 1
The Viewing Transformation
glTranslatef();
glRotatef();
gluLookAt();
The Modeling Transformation
glScalef();

7. Method for Transformation - 2
The Projection Transformation
Perspective
Orthographic
Order of Setting
glMatrixMode(types)
glLoadIdentity()
glFrustum() or gluPerspective(), glOrtho()

8. General-Purpose Transformation Commands
glMatrixMode(GLenum mode)
Specifies which matrix will be modified
GL_MODELVIEW, GL_PROJECTION, GL_TEXTURE
glLoadIdentity()
Sets the currently modifiable matrix to the 4*4 identity matrix

9. General-Purpose Transformation Commands
glMultMatrix{fd}(const Type *m)
Multiply the current matrix by the matrix passed in as an argument
glLoadMatrix{fd}(const Type *m)
Set the 16 values of the current matrix to those specified by m

10. Viewing and Modeling Transformations

11. Thinking about Transformation
To performing viewing or modeling transformation
glMatrixMode(GL_MODELVIEW);

12. 2 Types of Coordinate System
Example
glMatrixMode(GL_MODELVIEW);
glloadIdentity();
glMultiMatrixf(N);
glMultiMatrixf(M);
glBegin(GL_POINTS);
glVertex3f(v);
glEnd();
Grand, Fixed Coordinate System
Moving a Local Coordinate System

13. Modeling Transformation
Translate
Void glTranslate{fd}(x, y, z);
Rotate
Void glRotate{fd}(angle, x, y, z);
Scale
Void glScale{fd}(x, y, z);
glScalef(2.0, -1.5, 1.0);

14. Viewing Transformation - 1
glTranslate() or glRotate()
Moving forward camera
= Moving Backward Object
gluLookAt()
Void gluLookAt(
eyex, eyey, eyez,
centerx, centery, centerz,
upx, upy, upz);

15. Viewing Transformation - 2
Creating a Custom Utility Routine
Void PilotView(GLdouble planex, Gldouble planey, Gldouble planez, Gldouble roll, Gldouble pitch, Gldouble heading) {
glRotated(roll, 0.0, 0.0, 1.0);
glRotated(pitch, 0.0, 1.0, 0.0);
glRotated(heading, 1.0, 0.0, 0.0);
glTranslated(-planex, -planey, -planez); }

16. Projection Transformations

17. Projection Transformations
Purpose
To define a viewing volume
How an object is projected onto the screen
How to Clip the object
Setting for projection transformation
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

18. Perspective Projection - 1
Foreshortening
The farther, the smaller object appears in the final image
glFrustum(left, right,
bottm, top, near, far)

19. Perspective Projection - 2
gluPerspective(fov, aspect, near, far)

20. Orthographic Projection -1
View Volume
Rectangular parallelepiped

21. Orthographic Projection -2
glOrtho(left, right, bottom, top, near, far)
glOrtho2D (left, right, bottom, top)

22. Viewport Transformation

23. Defining the Viewport glViewport(x, y, width, height)
gluPerspective(fov, 2.0, near, far);
glViewport(0, 0, 400, 200);
The Transformed
Depth coordinates

24. Program Demo
Transformation\lesson1.exe