49 lines
3.7 KiB
Groff
49 lines
3.7 KiB
Groff
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|The OBJs use a lookup table that contains info on their X and Y position on |
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|the screen, their size, if they're flipped vertically or horizontally, their|
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|colour, and the actual data. |
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|The format you need to make the table is as follows: |
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|Spr. # Size Offset Explanation |
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| 0 Byte 0 xxxxxxxx x: X-location. |
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| Byte 1 yyyyyyyy y: Y-location. |
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| Byte 2 abcdeeeC a: Vertical flip. |
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| b: Horizontal flip. |
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| c: Playfield priority. |
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| d: Playfield priority. |
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| e: Pallete #. |
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| Byte 3 CCCCCCCC C: Character data. |
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| 1 Byte 4 xxxxxxxx x: X-location. |
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| Byte 5 yyyyyyyy y: Y-location. |
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| Byte 6 abcdeeeC a: Vertical flip. |
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| b: Horizontal flip. |
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| c: Playfield priority. |
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| d: Playfield priority. |
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| e: Pallete #. |
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| Byte 7 CCCCCCCC C: Character data. |
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|...and so on... |
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|Continue this table all the way down to OBJ #127 (out of 128). Don't think |
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|you're finished quite yet: There is one more table of data required. |
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|2 bits are defined for each OBJ (eg. byte #0 holds the info for OBJ 0, 1, 2,|
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|and 3; byte #1 holds the info for OBJ 4, 5, 6, and 7). Therefore, 128/4 is |
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|32 bytes of data for the following table: |
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| ab |
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| ||____Size toggle bit. |
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| |_____MSB of X-position bit. |
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|So, the 4 bytes/sprites + the block are put into the OAM table by consec- |
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|utive writes to the OAM data register. You first should set the OAM address |
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|to $0000, then shove your data into it. |
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|If you don't set the block after the OAM as well, the results are bad. All |
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|the data for the MSB stuff wouldn't be defined correctly, which would result|
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|in your entire OBJ table being wacko. Have atleast some 0's there or a table|
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|which you really want to use in the long run. |
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