All the information regarding 3D viewing is here. The whole presentation consists mainly of 3D viewing pipeline. This slide will make you clear about how one can have a 3d viewing of an object.

1. 3D
VIEWING
1
Presented by: Rabin BK
BSc.CSIT 4th Semester

2. 3-D viewing pipeline
 References
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3.  The viewing-pipeline in 3 dimensions is almost the same as the 2D-viewing-
pipeline
 An additional projection step is done, which is the reduction of 3D-data onto a
projection plane after the definition of the viewing direction and orientation
3D viewing pipeline
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4. Step 1 & 2: Object Coordinates and World-Coordinates
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World Coordinate System Viewing Coordinate System

5. To convert world-coordinates to viewing-coordinates a series of simple
transformations is needed.
 Mainly a translation of the coordinate origins onto each other and afterwards 3
rotations, such that the coordinate-axes also coincide (two rotations for the first
axis, one for the second axis, and the third axis is already correct then).
All these transformations can be merged by multiplication into one matrix,
which looks about like this:
Step 3: Viewing-Coordinates
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6. Step 4: Projection of object to viewing plane
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View Plane
Parallel Projection
• Coordinate are transferred to viewing plane along parallel
lines.
• Preserves relative size of object’s portions.
• Projection can be perpendicular or oblique to viewing plane.

7. Step 4: Projection of object to viewing plane contd..
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Perspective Projection
• Projection lines converge in a point behind viewing plane.
• Doesn’t preserve relative size but looks more realistic.

8. Step 4: Projection of object to viewing plane contd..
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Orthogonal (orthographic) projections
• Projection lines are parallel to normal.
• Used in engineering and architecture.
• Length and angles can be measured directly from drawings.
Plane View
Side
Elevation
View
Front
Elevation
View

9. Step 5: Clipping Window and View Volume
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Orthogonal
Projection View
Volume
Far
Clipping
Plane
Near
Clipping
Plane
View
Plane
Clipping
window
• Before projecting, we need to eliminate
the portion of scene that is outside the
viewing frustum
• Need to clip objects to the frustum
(truncated pyramid)

10.  This coordinate system refers to a subset of the screen space where the model window is
to be displayed.
 Typically the viewport will occupy the entire screen window, or even the entire screen,
but it is also possible to set up multiple smaller viewports within a single screen window.
 The normalized view volume cube extending from 1, 1, 1 to -1, -1, -1 is mapped to a
screen viewport, extending from xvmin , yvmin to xvmax , yvmax
Step 6: 3D Viewport Transformation
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11. Step 6: 3D Viewport Transformation
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 
   
 
min min
max max
The normalized view volume cube extending from 1, 1, 1 to
1,1,1 is mapped to a screen viewport, extending from ,
to , . information is stored for depth calculations. is
often
xv yv
xv yv z z
  
max min max min
max min max min
normviewvol,
3D screen
renormalized to the range from 0 to 1.0, yielding:
0 0
2 2
0 0
2 2
1 1
0 0
2 2
0 0 0 1
xv xv xv xv
yv yv yv yv
  
 
 
  
 
 
 
 
 
 
M
The normalized view volume cube extending
from 1, 1, 1 to -1, -1, -1 is mapped to a screen
viewport, extending from xvmin , yvmin to xvmax ,
yvmax

12. References
• https://www.cs.uic.edu/~jbell/CourseNotes/ComputerGraphics/Coordin
ates.html
• http://www.di.ubi.pt/~agomes/cg/teoricas/05e-viewing.pdf
• https://www.cs.drexel.edu/~david/Classes/CS430/Lectures/L-
12_Intro3DViewing.6.pdf
• https://www.cs.cmu.edu/afs/cs/academic/class/15462-
s09/www/lec/06/lec06.pdf
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13. Queries
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