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89 lines
2.6 KiB
C
89 lines
2.6 KiB
C
// ported from
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// https://odensskjegg.home.blog/2018/12/29/recreating-the-commodore-64-user-guide-code-samples-in-cc65-part-three-sprites/
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#include "common.h"
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/*{w:24,h:21,bpp:1,brev:1}*/
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const char sprite[3*21] = {
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0x00,0x7F,0x00,0x01,0xFF,0xC0,0x03,0xFF,0xE0,
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0x03,0xE7,0xE0,0x07,0xD9,0xF0,0x07,0xDF,0xF0,
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0x07,0xD9,0xF0,0x03,0xE7,0xE0,0x03,0xFF,0xE0,
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0x03,0xFF,0xE0,0x02,0xFF,0xA0,0x01,0x7F,0x40,
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0x01,0x3E,0x40,0x00,0x9C,0x80,0x00,0x9C,0x80,
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0x00,0x49,0x00,0x00,0x49,0x00,0x00,0x3E,0x00,
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0x00,0x3E,0x00,0x00,0x3E,0x00,0x00,0x1C,0x00
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};
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// Pre-calculated sinus values
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const char yValues[] = {
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32, 35, 38, 41, 44, 47, 49, 52,
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54, 56, 58, 60, 61, 62, 63, 63,
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64, 63, 63, 62, 61, 60, 58, 56,
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54, 52, 49, 47, 44, 41, 38, 35,
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32, 28, 25, 22, 19, 16, 14, 11,
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9, 7, 5, 3, 2, 1, 0, 0,
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0, 0, 0, 1, 2, 3, 5, 7,
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9, 11, 14, 16, 19, 22, 25, 28
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};
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// Raster wait with line argument
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void rasterWait(unsigned char line) {
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while (VIC.rasterline < line) ;
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}
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int main (void)
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{
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unsigned char n, t;
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int rx, x;
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char sx, msb;
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VIC.bgcolor0 = 3;
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__asm__("SEI"); // clear interrupts to avoid glitching
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for (n = 0 ; n < sizeof(sprite) ; n++) {
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POKE(832 + n, sprite[n]);
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}
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VIC.spr_ena = 255;
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for (t = 0 ; t < 8 ; t++) {
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POKE(2040 + t, 13); // Set sprite x data from 13th block for all sprites
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}
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do {
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for (x = 0 ; x < 550; x++) {
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msb = 0; // MSB of X coordinates
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// Wait until raster hits position 250 before drawing upper sprites
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rasterWait(250);
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// Set border color, which indicates the raster position
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VIC.bordercolor = 1;
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rx = x;
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for (t = 0 ; t < 8 ; t++) {
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rx -= 24;
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if (rx >= 0 && rx < 366) {
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// Usually I would calculate the sprite X coordinate using
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// the expression sx = rx % 256, but bitwise operation is
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// significant faster
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sx = rx & 255;
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if (rx > 255) {
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// Set MSB of x coordinate for sprite if x position > 255
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msb |= 1 << t;
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}
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VIC.spr_pos[t].x = sx;
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// Y position is an indirect Sinus function of X, using array
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// index for retrieving the Y value
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VIC.spr_pos[t].y = yValues[sx & 63] + 40;
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} else {
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VIC.spr_pos[t].x = 0;
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}
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}
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VIC.spr_hi_x = msb; // Set MSB of x coordinate
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// Wait until raster hits position 135 before drawing lower sprites
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rasterWait(135);
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VIC.bordercolor = 2; // Set border color
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for (t = 0 ; t < 8 ; t++) {
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// Add 128 to current sprite Y position
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VIC.spr_pos[t].y += 128;
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}
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}
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} while (1);
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return EXIT_SUCCESS;
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}
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