initial commit

oscar64/samples/scrolling/tunnel.c

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+#include <c64/vic.h>
+#include <c64/memmap.h>
+#include <string.h>
+#include <stdlib.h>
+
+// Screen and color space
+#define screen ((byte *)0x0400)
+#define color ((byte *)0xd800)
+
+// Macro for easy access to screen space
+#define sline(x, y) (screen + 40 * (y) + (x))
+
+// Column buffer for one prepared column of tunnel
+char rbuff[25];
+
+// Copy the prepared tunnel column to screen
+void expand(char x)
+{
+	// Unroll for each row
+#assign y 0		
+#repeat
+	sline(0, y)[x] = rbuff[y];
+#assign y y + 1
+#until y == 25
+}
+
+// Scrolling left, copying new column.  This is split into two
+// unrolled sections so the update of the new column can race the
+// beam
+
+void scrollLeft(void)
+{
+	// First 12 rows scroll left and copy new column
+	for(char x=0; x<39; x++)
+	{
+#assign y 0		
+#repeat
+		sline(0, y)[x] = sline(1, y)[x];
+#assign y y + 1
+#until y == 12
+	}
+#assign y 0		
+#repeat
+	sline(0, y)[39] = rbuff[y];
+#assign y y + 1
+#until y == 12
+
+	// Final 13 rows scroll left and copy new column
+	for(char x=0; x<39; x++)
+	{
+#assign y 12	
+#repeat
+		sline(0, y)[x] = sline(1, y)[x];
+#assign y y + 1
+#until y == 25
+	}
+#assign y 12	
+#repeat
+	sline(0, y)[39] = rbuff[y];
+#assign y y + 1
+#until y == 25
+}
+
+// Scrolling right, copying new column.  This is split into two
+// unrolled sections so the update of the new column can race the
+// beam
+
+void scrollRight(void)
+{
+	for(char x=39; x>0; x--)
+	{
+#assign y 0		
+#repeat
+		sline(0, y)[x] = sline(-1, y)[x];
+#assign y y + 1
+#until y == 12
+	}
+#assign y 0		
+#repeat
+	sline(0, y)[0] = rbuff[y];
+#assign y y + 1
+#until y == 12
+
+	for(char x=39; x>0; x--)
+	{
+#assign y 12	
+#repeat
+		sline(0, y)[x] = sline(-1, y)[x];
+#assign y y + 1
+#until y == 25
+	}	
+#assign y 12	
+#repeat
+	sline(0, y)[0] = rbuff[y];
+#assign y y + 1
+#until y == 25
+}
+
+// Top and bottom row of the tunnel
+
+char ytop[256], ybottom[256];
+
+// Prepare one column of the tunnel
+
+void prepcol(char xi)
+{
+	char		yt, yb;
+	signed char dyt, dyb;
+
+	// Current height of top and bottom
+	yt = ytop[(char)(xi + 0)];
+	yb = ybottom[(char)(xi + 0)];
+
+	// Height of column to the left for diagonal
+	dyt = yt - ytop[(char)(xi - 1)];
+	dyb = yb - ybottom[(char)(xi - 1)];				
+
+	// Fill top, center and bottom range
+	for(char i=0; i<yt; i++)
+		rbuff[i] = 160;
+	for(char i=yt; i<yb; i++)
+		rbuff[i] = 32;
+	for(char i=yb; i<25; i++)
+		rbuff[i] = 160;
+
+	// Select transitional characters based on slope
+	if (dyt < 0)
+		rbuff[yt] = 105;
+	else if (dyt > 0)
+		rbuff[yt - 1] = 95;
+
+	if (dyb < 0)
+		rbuff[yb] = 233;
+	else if (dyb > 0)
+		rbuff[yb - 1] = 223;
+
+}
+
+// Initialize tunnel with "random" data
+void buildTunnel(void)
+{
+	signed char yt = 1, yb = 24, dyt = 1, dyb = -1;
+
+	for(int i=0; i<256; i++)
+	{
+		unsigned r = rand();
+
+		if (!(r & 0x00e0))
+			dyt = -dyt;
+		if (!(r & 0xe000))
+			dyb = -dyb;
+
+		yt += dyt;
+		yb += dyb;
+		if (yt < 0)
+		{
+			yt = 0;
+			dyt = 1;
+		}
+		if (yb > 25)
+		{
+			yb = 25;
+			dyb = -1;
+		}
+
+		ytop[i] = yt;
+		ybottom[i] = yb;
+
+		if (yt + 5 > yb)
+		{
+			dyt = -1;
+			dyb = 1;
+		}
+	}
+
+}
+
+int main(void)
+{
+	// Clear the screen
+
+	memset(screen, 0x20, 1000);
+	memset(color, 7, 1000);
+
+	vic.color_back = VCOL_BLACK;
+	vic.color_border = VCOL_BLACK;
+
+	// Build tunnel
+
+	buildTunnel();
+
+	// Initial fill of screen
+
+	for(char i=0; i<40; i++)
+	{
+		prepcol(i);
+		expand(i);
+	}
+
+	// Now start moving
+	int	xpos = 0, dx = 0, ax = 1;
+	int	xi = 0, pxi = 0;
+
+	for(;;)
+	{
+		// Random change of direction
+		unsigned r = rand();
+		if ((r & 127) == 0)
+			ax = -ax;
+
+		// Acceleration
+		dx += ax;
+		if (dx > 32)
+			dx = 32;
+		else if (dx < -32)
+			dx = -32;
+
+		// Movement
+		xpos += dx;
+		pxi = xi;
+		xi = xpos >> 5;
+
+		// Check if we cross a character boundary, and if so prepare
+		// the new column
+		if (pxi < xi)
+			prepcol(xi + 39);
+		else if (pxi > xi)
+			prepcol(xi + 0);
+
+		// Wait one frame
+		vic_waitTop();
+		vic_waitBottom();
+
+		// Update pixel level scrolling
+		vic.ctrl2 = (7 - (xpos >> 2)) & 7;
+
+		// Character level scrolling if needed
+		if (pxi < xi)
+			scrollLeft();
+		else if (pxi > xi)
+			scrollRight();
+	}
+
+	return 0;
+
+}