Commodore Amiga A2000 - Figure 6-5 Use of the FCI Bit - Bit Is a 0; Figure 6-6 Use of the FCI Bit - Bit Is a 1

There is another bit (FILL_CARRYIN or bit 3 in BLTCON1) that forces the area "outside"
the lines be filled; for the above example, with inclusive fill, the output would be;
11100111-11111111
with exclusive fill, the output would be;
11100011-11110111
BEFORE AFTER
____________________ ___________________
| | | |
| 1 1 1 1 | | 11111 11111 |
| 1 1 1 1 | | 11111 11111 |
| 1 1 1 1 | | 1111 1111 |
| 1 1 1 1 | | 111 111 |
| 11 11 | | 11 11 |
| 1 1 1 1 | | 111 111 |
| 1 1 1 1 | | 1111 1111 |
| 1 1 1 1 | | 11111 11111 |
|____________________| |___________________|
Figure 6-5: Use of the FCI Bit - Bit Is a 0
If the FCI bit is a 1 instead of a 0, the area outside the lines is filled with ls and the area
inside the lines is left with 0s in between.
BEFORE AFTER
____________________ ___________________
| | | |
| 1 1 1 1 | |111 1111111 11|
| 1 1 1 1 | |111 11111111 11|
| 1 1 1 1 | |1111 111111111 11|
| 1 1 1 1 | |11111 1111111111 11|
| 11 11 | |1111111111111111111|
| 1 1 1 1 | |11111 1111111111 11|
| 1 1 1 1 | |1111 111111111 11|
| 1 1 1 1 | |111 11111111 11|
|____________________| |___________________|
Figure 6-6: Use of the FCI Bit - Bit Is a 1
If you wish to produce very sharp, single-point vertices, exclusive-fill enable must be
used. Figure 6-7 shows how a single-point vertex is produced using exclusive-fill enable.
- Blitter Hardware 179 -