Intel 815 Manuel D’Utilisation

  

253 

The following provides programming hints/rules for 3D, Motion Compensation, and Stretch Blitter 
operations. 

•  Must declare a Drawing Rectangle packet first before Scissor Rectangle packet 
•  Coordinates of Drawing Rectangle must be X

max 

> X

min

 and Y

max 

> Y

min

 

•  Drawing Rectangle width and height must be greater than 1pixel for Rectangle primitives. 
•  Drawing Rectangle X & Y coordinates must be within the screen size. The drawing rectangle must 

be clipped to screen coordinates before send to hardware. However, the origin of the drawing 
rectangle can be negative since it is need not be clipped. It is the reference point (origin) of all the 
primitives and scissor rectangle that belong to the drawing rectangle. 

 

0,0

Origin of

Scissor

Xmin, Ymin

Xmax, Ymax

Screen

scissor.vsd

 

•  Small Triangle Filter can only be enabled if the horizontal and vertical bias values (defined in Dest 

Buffer variable packet) are programmed to (0000,0000) or (1000,1000). This is corresponds to the 
pixel center of (0,0) and (0.5,0.5), respectively. 

•  A Texture palette load must contain all 256 entries. Even if only one entry needs to be updated, all 

256 entries in the Texture palette must be loaded using the texture palette load packet. 

•  Color Key and Chroma Key cannot be enabled at the same time. 
•  In mult-texture, Colorkey and Chromkey only compare with Map 0 texels and not on Map 1 texels. 
•  Any programming change made to the Mapping Engine Cache Enable state variable must be 

followed by a 3D pipeline flush, otherwise pixel corruption will occur. For example, software 
changes the state of the Mapping Engine cache by flipping the bit Mapping Cache Enable using the