Chapter 3 Viewing

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 • glTranslatef(); • glRotatef(); • 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