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8bitworkshop/presets/c64/upandaway.c

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2019-12-21 21:06:25 +00:00
// ported from
// https://odensskjegg.home.blog/2018/12/29/recreating-the-commodore-64-user-guide-code-samples-in-cc65-part-three-sprites/
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <peekpoke.h>
#include <c64.h>
/*{w:24,h:21,bpp:1,brev:1}*/
const char sprite[3*21] = {
0x00,0x7F,0x00,0x01,0xFF,0xC0,0x03,0xFF,0xE0,
0x03,0xE7,0xE0,0x07,0xD9,0xF0,0x07,0xDF,0xF0,
0x07,0xD9,0xF0,0x03,0xE7,0xE0,0x03,0xFF,0xE0,
0x03,0xFF,0xE0,0x02,0xFF,0xA0,0x01,0x7F,0x40,
0x01,0x3E,0x40,0x00,0x9C,0x80,0x00,0x9C,0x80,
0x00,0x49,0x00,0x00,0x49,0x00,0x00,0x3E,0x00,
0x00,0x3E,0x00,0x00,0x3E,0x00,0x00,0x1C,0x00
};
// Pre-calculated sinus values
const char yValues[] = {
32, 35, 38, 41, 44, 47, 49, 52,
54, 56, 58, 60, 61, 62, 63, 63,
64, 63, 63, 62, 61, 60, 58, 56,
54, 52, 49, 47, 44, 41, 38, 35,
32, 28, 25, 22, 19, 16, 14, 11,
9, 7, 5, 3, 2, 1, 0, 0,
0, 0, 0, 1, 2, 3, 5, 7,
9, 11, 14, 16, 19, 22, 25, 28
};
// Raster wait with line argument
void rasterWait(unsigned char line) {
while (VIC.rasterline < line) ;
}
int main (void)
{
unsigned char n, t;
int rx, x;
char sx, msb;
VIC.bgcolor0 = 3;
__asm__("SEI"); // clear interrupts to avoid glitching
for (n = 0 ; n < sizeof(sprite) ; n++) {
POKE(832 + n, sprite[n]);
}
VIC.spr_ena = 255;
for (t = 0 ; t < 8 ; t++) {
POKE(2040 + t, 13); // Set sprite x data from 13th block for all sprites
}
do {
for (x = 0 ; x < 550; x++) {
msb = 0; // MSB of X coordinates
// Wait until raster hits position 250 before drawing upper sprites
rasterWait(250);
// Set border color, which indicates the raster position
VIC.bordercolor = 1;
rx = x;
for (t = 0 ; t < 8 ; t++) {
rx -= 24;
if (rx >= 0 && rx < 366) {
// Usually I would calculate the sprite X coordinate using
// the expression sx = rx % 256, but bitwise operation is
// significant faster
sx = rx & 255;
if (rx > 255) {
// Set MSB of x coordinate for sprite if x position > 255
msb |= 1 << t;
}
VIC.spr_pos[t].x = sx;
// Y position is an indirect Sinus function of X, using array
// index for retrieving the Y value
VIC.spr_pos[t].y = yValues[sx & 63] + 40;
} else {
VIC.spr_pos[t].x = 0;
}
}
VIC.spr_hi_x = msb; // Set MSB of x coordinate
// Wait until raster hits position 135 before drawing lower sprites
rasterWait(135);
VIC.bordercolor = 2; // Set border color
for (t = 0 ; t < 8 ; t++) {
// Add 128 to current sprite Y position
VIC.spr_pos[t].y += 128;
}
}
} while (1);
return EXIT_SUCCESS;
}