Texturing - NEC µPD72257 Preliminary User's Manual

Drawing Engine

8.5.10 Texturing

8.5.10.1
The texture unit can cover any primitive with a picture. The picture can be
stretched, shared, rotated and translated with the texture unit in one step. To
avoid aliasing the result can be filtered bilinear in u and v directions.
Mathematical background
The arbitrary mapping problem is completely determined by a mapping from 3
points in object space (x,y) to 3 points in texture space (u,v).
Let there be the following mapping:
x
 
u
~  
 
 0 
0
p p    
= ⇒ = =
 
0 y 0
v
 
 
0
0
x u
  ~   
 
1 1
p     p      
= ⇒ = =
1 1
y v
    
1 1
x u
  ~  
 
2 2
p =     ⇒ p =     =
2 2
y v
   
2 2
While w is the width of the texture and h is the height of the texture.
Examine the following picture in object space.
difference vectors are taken for calculations:

 
d = p − p
1 1 0

 
d = p − p
2 2 0
This is equivalent to transforming from coordinate system O to coordinate system
O'.
Preliminary User's Manual S19203EE1V3UM00
0
 
   
0
 
w

 
0

0
 
   
h
 
Chapter 8
To simplify calculations the
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