NEC µPD72257 Preliminary User's Manual page 230

Chapter 8
8.5.3.3
230
Example
If a straight line is given by the points P
the following:
x − x
 

  
  1 0  
∆ p = p − p = =  
1 0
y − y
  
1 0
The normal vector (perpendicular but not unit size) is then
− ∆ y
 

n =    
∆ x
 
The not normalized distance between edge and origin is then
 
p n = − x ∆ y + y ∆ x
0 0 0
The limiter parameters would be
start = − x ∆ y + y ∆ x
0 0
xadd = − ∆ y
yadd = ∆ x
In the normalized case normal vector is
− ∆ y
 

n =     / ∆ x 2 + ∆ y 2
∆ x
 
The distance between edge and origin is
 
( )
p n = − x ∆ y + y ∆ x / ∆ x
0 0 0
The limiter parameters would be
( )
start = − x ∆ y + y ∆ x / ∆
0 0
xadd y x 2
= − ∆ / ∆ +
yadd = ∆ x / ∆ x 2 + ∆
Normalization is only needed if antialiasing is used. The driver contains a
optimized inverse square root to speed up the normalization.
Preliminary User's Manual S19203EE1V3UM00
and P then the values are calculated as
0 1
x
∆

 
y
∆

2 + ∆ y 2
2 2
x + ∆ y
y 2
∆
y 2
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