Subject: RE: [stella] RPG Development (iii) From: "David Schweinsberg" <david@xxxxxxxxxxxxxxxxx> Date: Sun, 4 Jul 1999 22:40:50 +0100 |
>One thing I've noticed about it is that seems to use more playfield colors >than just 2. How are the colors managed? You're right, two colours can be used in the terrain + black for the non-map area. This places a restriction on the world-design by needing a horizontal stretch of 8 squares before switching colours. You will notice on the island at the bottom of the world that the forest between the sea and the "grassy plain" is 8 squares wide. This restriction doesn't exist vertically. With clever design, I'm hoping the average player will never notice. The HMOVE lines form the black background on the left, and the right is handled by changing COLUBK to black, followed by changing COLUPF to black. By ensuring the first two bits of PF0 are set to 0 (the same two that are hidden by HMOVE), and the last two bits of PF2 (the right-hand side of the map) are always 1, then we get a clean switch from colour to black. Because there are two timing sensitive issues to be handled for each row (positioning of GRP0 and changing COLUPF/COLUBK), there are 9 separate pieces of code to handle line 2 of each row - one for each GRP0 position. Because both PF and BK have been set to black and therefore never see PF graphics on the right side of the screen, we don't need to modify PF registers every scanline, so we get time to set GRP0 & GRP1 values. Regards, David Schweinsberg -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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