mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-25 03:34:05 +00:00
108 lines
2.0 KiB
C
108 lines
2.0 KiB
C
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#include "common.h"
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//#link "common.c"
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#include "rasterirq.h"
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//#link "rasterirq.s"
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#include "bcd.h"
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//#link "bcd.c"
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extern const unsigned char sinustable[0x100];
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//#link "sinustable.c"
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///// VARIABLES
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byte frame = 0;
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byte target_y;
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byte fld_offsets[25];
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///// FUNCTIONS
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void line_crunch() {
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// load scroll y
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asm("lda %v", target_y);
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asm("and #7");
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asm("ora #$18");
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asm("tax");
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// get current raster line
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asm("lda $d012");
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// wait for next raster line
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asm("@loop:");
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asm("cmp $d012");
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asm("beq @loop");
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// set y scroll (ctrl1)
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asm("stx $d011");
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}
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static byte target_line = 0;
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static byte row;
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static byte offset;
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void display_list(void) {
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VIC.bgcolor[0] = COLOR_CYAN;
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VIC.bordercolor = COLOR_BLUE;
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// set initial YSCROLL
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SET_SCROLL_Y(fld_offsets[0]);
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// set first target scanline
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target_line = 48 + (fld_offsets[0] & 7);
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// each row has its own FLD gap
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for (row=1; row<25; row++) {
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// get this row's gap distance
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offset = fld_offsets[row];
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// fire IRQ 3 lines before target
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target_y = target_line - 3;
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DLIST_NEXT(target_y);
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// change Y scroll to avoid badline
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line_crunch();
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// set Y scroll for new badline
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target_y = target_line + offset;
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line_crunch();
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// set target line for next IRQ
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target_line += 8 + offset;
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VIC.bgcolor[0] = row;
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// exit loop if integer overflow
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if (target_line < 48) break;
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}
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DLIST_RESTART(30);
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}
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void main() {
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int i;
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clrscr();
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memset(COLOR_RAM, COLOR_BLUE, 1000);
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for (i=0; i<40*25; i++)
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POKE(0x400 + i, 205 + (rand() & 1));
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for (i=40*25; i<1024; i++)
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POKE(0x400 + i, i);
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for (i=0; i<1024; i+=40)
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POKE(0x400 + i, 122);
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SET_VIC_BITMAP(0x1000);
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DLIST_SETUP(display_list);
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// game loop, repeat forever
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while (1) {
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// wait for end of frame
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waitvsync();
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// animate and set scroll_y
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frame += 4;
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// set FLD offsets via sinus table
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for (i=0; i<25; i++) {
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fld_offsets[i] = sinustable[frame + i*8] >> 5;
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}
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}
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}
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