Assignment 2 Phase 1

1
Assignment 2 Phase 1

• Transformation
• Back-face culling
• View frustum culling

2
Outline

• Implement the transformation.
• Viewing transformation
• Projection transformation
• Perspective division
• Viewport transformaion
• Implement back-face culling.
• Implement view frustum culling.

3
Input and Output

• Input .view .obj .mtl
• Same as assignment 1
• Output Wireframe of the obj with back-face
  culling

4
Transformation 1/3
Modelview Matrix
Viewport Transformation
Projection Matrix
Perspective Division
Vertex

• Viewing transformaion
• Tview B T
• Implement gluLookat() in OpenGL

5
Transformation 2/3

• Projection transformation
• Tp NSH
• Implement gluPerspective() in OpenGL, so do not
  need to implement H

6
Transformation 3/3

• Perspective division
• All X,Y,Z,W are divided by W.
• Viewport transformation
• Tv T S

7
Back-face culling

• You can perform back-face culling in
• World cord.
• View cord.
• ZN lt 0
• Window cord.
• Clock wise

1
Back face
3
2
8
View frustum culling

• eliminate the polygon that complete outside the
  view frustum.
• Bonus view frustum clipping
• Remove the part of polygon that outside the view
  frustum.

9
How to draw wireframe?

• Render the image using
• glBegin(GL_LINE_LOOP)
• glVertex2i(x,y)
• glEnd()

10
What to do in reshape function?

• void GL_reshape(GLsizei w, GLsizei h)
• glViewport(viewport-gtx, viewport-gty,
• viewport-gtwidth,
  viewport-gtheight)
• glMatrixMode(GL_PROJECTION)
• glLoadIdentity()
• gluOrtho2D(viewport-gtx, viewport-gtwidth,
• viewport-gty,
  viewport-gtheight)
• glMatrixMode(GL_MODELVIEW)
• glLoadIdentity()

11
UI requirement

• Show an input command line.
• Please input the file name.
• If I type box, then read box.obj and box.view
  etc.