initial commit

2026-07-18 20:34:55 +02:00
commit 59ad004c96
474 changed files with 226635 additions and 0 deletions
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+#include <string.h>
+#include <conio.h>
+#include <c64/vic.h>
+
+#define Screen	((char *)0x0400)
+#define Color	((char *)0xd800)
+
+// Lookup table for squares from 0..255
+__striped unsigned sqb[256];
+
+// Shift byte right and left by 4
+char shlb4[256], shrb4[256];
+
+#pragma align(sqb, 256);
+
+// Square an unsigned int into an unsigned long
+inline unsigned long ssquare(unsigned x)
+{
+	// Split into low byte and highbyte, so we have x = a + 0x100 * b
+
+	unsigned	a = x & 0xff;
+	unsigned	b = x >> 8;
+
+	// So now we calculate (a + 0x100 * b)²
+	// Result will be a² + 0x100 * 2 * a * b + 0x10000 * b²
+	// with 2 * a * b == (a + b)² - a² - b²
+
+	// We can cover all cases with the square table except if a + b >= 0x100
+	// in this case we have abp := a + b - 0x100
+	// (abp + 0x100)² == abp² + 2 * 0x100 * abp + 0x10000
+
+	// Get squares of the bytes and the sum of the bytes
+	unsigned	a2 = sqb[a], b2 = sqb[b];
+	unsigned	apb = a + b;
+
+	// First approximation approximation 
+	// a² + 0x10000 * b²
+	unsigned long sum = a2 + ((unsigned long)b2 << 16);
+
+	// Check if a + b >= 0x100
+	if (apb & 0xff00)
+	{
+		apb &= 0xff;
+		sum += 0x1000000UL;
+		sum += (unsigned long)apb << 17;
+		sum += (unsigned long)sqb[apb] << 8;
+	}
+	else
+	{
+		apb &= 0xff;
+		sum += (unsigned long)sqb[apb] << 8;
+	}
+
+	// Now w have a² + 0x1000 * b² + (a + b)²
+
+	sum -= (unsigned long)a2 << 8;
+	sum -= (unsigned long)b2 << 8;
+
+	// And finally the complete result
+	return sum;
+}
+
+// Signed square of x
+inline long sq(int x)
+{
+	if (x < 0)
+		x = -x;
+	return ssquare(x);
+}
+
+// Colors to fill in the different levels
+static const char colors[32] = {
+	VCOL_BLUE,
+	VCOL_LT_BLUE,
+	VCOL_WHITE,
+	VCOL_LT_GREEN,
+	VCOL_GREEN,
+	VCOL_YELLOW,
+	VCOL_ORANGE,
+	VCOL_RED,
+	VCOL_PURPLE,
+
+	VCOL_BLUE,
+	VCOL_BLUE,
+	VCOL_LT_BLUE,
+	VCOL_LT_BLUE,
+	VCOL_WHITE,
+	VCOL_WHITE,
+	VCOL_LT_GREEN,
+	VCOL_LT_GREEN,
+	VCOL_GREEN,
+	VCOL_GREEN,
+	VCOL_YELLOW,
+	VCOL_YELLOW,
+	VCOL_ORANGE,
+	VCOL_ORANGE,
+	VCOL_RED,
+	VCOL_RED,
+	VCOL_PURPLE,
+	VCOL_PURPLE,
+
+	VCOL_LT_GREY,
+	VCOL_LT_GREY,
+	VCOL_MED_GREY,
+	VCOL_MED_GREY,
+	VCOL_DARK_GREY,
+};
+
+inline int shr12(long l)
+{
+	char b3 = (l >> 24) & 0xff;
+	char b2 = (l >> 16) & 0xff;
+	char b1 = (l >>  8) & 0xff;
+	char a0 = shrb4[b1] | shlb4[b2];
+	char a1 = shrb4[b2] | shlb4[b3];
+	return a0 | (a1 << 8);
+}
+
+// Return color for a given coordinate in the complex plane using
+// 12.4bit fixed numbers using m'=m²+b
+
+inline char fcolor(int xz, int yz)
+{
+	// Start value for iteration is the offset value itself
+
+	int		x = xz, y = yz;
+
+	// Iterate up to 32 steps
+
+	for(int i=0; i<32; i++)
+	{
+		// Build squares of real and imaginary component
+		long xx = sq(x), yy = sq(y), xxyy = sq(x + y);
+
+		long xxpyy = xx + yy;
+		
+		// Use squares to check for exit condition of sure
+		// to progress towards infinity
+		if (xxpyy >= 4L * 4096 * 4096) return colors[i];
+		
+		// Next iteration values using complex arithmetic
+		// Mx' = Mx² - My² + Bx
+		// My' = 2 * Mx * My + By = (Mx + My)² - Mx² - My² + By		
+		x = shr12(xx - yy + 2048) + xz;
+		y = shr12(xxyy - xxpyy + 2048) + yz;
+	}
+	
+	// More than maximum number of iterations, so assume progress
+	// towards zero
+
+	return VCOL_BLACK;
+}
+
+// Fill a row with color
+void fill_row(char py, int cix, int yz, int cis)
+{
+	int	xz = cix;
+	for(int px=0; px<40; px++)
+	{		
+		Color[py * 40 + px] = fcolor(xz, yz);
+		xz += cis;
+	}	
+}
+
+// Fill a column with color
+void fill_column(char px, int xz, int ciy, int cis)
+{
+	int	yz = ciy;
+	for(int py=0; py<25; py++)
+	{		
+		Color[py * 40 + px] = fcolor(xz, yz);
+		yz += cis;
+	}	
+}
+
+// Fill the complete image
+void fill_image(int cix, int ciy, int cis)
+{
+	int		yz = ciy;
+	for(int py=0; py<25; py++)
+	{
+		fill_row(py, cix, yz, cis);
+		yz += cis;	
+	}
+}
+
+// Scroll screen to the left
+void scroll_left(void)
+{
+	for(char x=0; x<39; x++)
+	{
+		#pragma unroll(full)
+		for(char y=0; y<25; y++)
+		{
+			Color[y * 40 + x] = Color[y * 40 + x + 1];
+		}
+	}
+}
+
+// Scroll screen to the right
+void scroll_right(void)
+{
+	for(signed char x=38; x>=0; x--)
+	{
+		#pragma unroll(full)
+		for(char y=0; y<25; y++)
+		{
+			Color[y * 40 + x + 1] = Color[y * 40 + x];
+		}
+	}
+}
+
+// Scroll screen up
+void scroll_up(void)
+{
+	for(char x=0; x<40; x++)
+	{
+		#pragma unroll(full)
+		for(char y=0; y<24; y++)
+		{
+			Color[y * 40 + x] = Color[(y + 1) * 40 + x];
+		}
+	}
+}
+
+// Scroll screen down
+void scroll_down(void)
+{
+	for(char x=0; x<40; x++)
+	{
+		#pragma unroll(full)
+		for(char y=0; y<24; y++)
+		{
+			Color[(24 - y) * 40 + x] = Color[(23 - y) * 40 + x];
+		}
+	}
+}
+
+int main(void)
+{
+	// Initialize square table
+	for(unsigned i=0; i<256; i++)
+	{
+		sqb[i] = i * i;
+		shlb4[i] = i << 4;
+		shrb4[i] = i >> 4;
+	}
+
+	// Clear screen
+	memset(Screen, 160, 1024);
+
+	// Start coordinates in float
+	float cx = -0.4;
+	float cy = 0.0;
+	float cw = 3.2;
+
+	// Convert to top, left and step in 12.4 fixed point
+	int		cix = (int)((cx - 0.5 * cw) * 4096);
+	int		ciy = (int)((cy - 12.0 * cw / 40.0) * 4096);
+	int		cis = (int)(cw / 40.0 * 4096);
+
+	// Initial image
+	fill_image(cix, ciy, cis);
+
+	for(;;)
+	{
+		// Wait for keypress
+		char ch = getch();
+
+		switch (ch)
+		{
+		case 'S':
+			ciy += cis;
+			scroll_up();
+			fill_row(24, cix, ciy + 24 * cis, cis);
+			break;
+		case 'W':
+			ciy -= cis;
+			scroll_down();
+			fill_row(0, cix, ciy, cis);
+			break;
+		case 'A':
+			cix -= cis;
+			scroll_right();
+			fill_column(0, cix, ciy, cis);
+			break;
+		case 'D':
+			cix += cis;
+			scroll_left();
+			fill_column(39, cix + 39 * cis, ciy, cis);
+			break;
+		case '+':
+			cix += 20 * cis;
+			ciy += 12 * cis;
+			cis = cis * 2 / 3;
+			cix -= 20 * cis;
+			ciy -= 12 * cis;
+			fill_image(cix, ciy, cis);
+			break;
+		case '-':
+			cix += 20 * cis;
+			ciy += 12 * cis;
+			cis = cis * 3 / 2;
+			cix -= 20 * cis;
+			ciy -= 12 * cis;
+			fill_image(cix, ciy, cis);
+			break;
+		}
+	}
+	
+	return 0;
+}