CGA OPERATIONS COVERED
r()- rotate s()- size t()- translate
INTRODUCTION
The rotate r( ), size s ( ) and translate t( ) shape functions are neighbors in the alphabet and they are used with each other to manipulate scopes, the imaginary box that surrounds a shape and defines its maximum x, y and z dimensions.
It will be important to know these before we start shaping buildings and modeling facades in Tutorials 6 and 7.
Rotate: In Figure A, a flat plane is rotated 45 degrees on it’s x, y and z axes, which are indicated with blue lines. The parameters for the three planes are: x-axis r(45,0,0); y-axis r(0,45,0); z-axis r(0,0,45). The planes can also be rotated in the opposite directions using negative values.
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Size: Here, we will resize shapes by adjusting their scope. When we change the x, y and/or z dimensions of the scope, whatever shape is inside will change dimensions. Each primitive cone starts with 12 sides, a diameter of 20 meters and a height of 40 meters as shown in the code block. See what happens as we resize the x, y or z of each shape’s scope: Increasing x or z makes as in Cones 2 & 3 widens them in one direction. Increasing y makes Cone 4 taller. Giving z a value of 1 actually flattens Cone 5. Depending on the adjustment to the scope, the shape may have to be translated (moved) to its desired position on the landscape.
StartCone -->
primitiveCone(12,20,40)
color("#FFFF00")
# Resize X
Cone2-->
primitiveCone(12,20,40)
color("#FFFF00")
s(70,20,20)
# Resize Z
Cone3 -->
primitiveCone(12,20,40)
color("#FFFF00")
s(20,20,70)
# Resize Y
Cone4 -->
primitiveCone(12,20,40)
color("#FFFF00")
s(20,80,20)
# Flatten Z
Cone5 -->
primitiveCone(12,20,40)
color("#FFFF00")
s(20,20,1))
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Translate: We will move a 10×10 meter flat plane along the x, y and z axes.
- The yellow square represents the starting coordinates of t(0,0,0).
- Red: t(20,0,0) – movement along the x-axis
- Green: t(0,10,0) – movement along the y-axis (straight up)
- Blue: t(0,0,20) – movement along the z-axis
Start-->
primitiveQuad(10,10)
color("#FFFF00") // Yellow
t(0,0,0)
Start2-->
primitiveQuad(10,10)
color("#FF0000") // Red
t(20,0,0)
Start3-->
primitiveQuad(10,10)
color("#00FF00") // Green
t(0,10,0)
Start4-->
primitiveQuad(10,10)
color("#0000FF") // Blue
t(0,0,20)