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HARD/EDGE.C

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+#include <stdio.h>
+#include <graph.h>
+
+char far *vram=(char far *)0xa0000000L;
+
+int	edge[512];
+
+int ep[200];
+int ec;
+struct
+{
+	int	c,next;
+	int	y1,y2;
+	long	x1,x; // x used, x1=original
+	long	dx;
+} e[256];
+
+int	list[256],listc;
+
+unsigned draworders[32000],dop;
+
+void	pass3(void)
+{
+	unsigned int u,ut,i,c;
+	for(i=c=u=0;i<dop;i+=2)
+	{
+		ut=draworders[i+0];
+		while(u<ut) vram[u++]=c;
+		c^=draworders[i+1];
+	}
+}
+
+void	pass2(void)
+{
+	int	j,k,i,y,c;
+	long	x,lx;
+	listc=0;
+	dop=0;
+	for(y=0;y<200;y++)
+	{
+		// add new ones this row
+		i=ep[y];
+		while(i)
+		{
+			list[listc++]=i;
+			e[i].x=e[i].x1;
+			i=e[i].next;
+		}
+		// sort list
+		for(k=1;k<listc;k++)
+		{
+			x=e[i=list[k]].x;
+			for(j=k-1;j>=0 && x<e[list[j]].x;j--) 
+				list[j+1]=list[j];
+			list[j+1]=i;
+		}
+		// do list & kill completed ones
+		for(k=j=0;j<listc;j++)
+		{	
+			i=list[j];
+			if(y>=e[i].y2) continue;
+			if(k!=j) list[k]=i;
+			k++;
+			x=e[i].x;
+			if(lx==x) draworders[dop-1]^=e[i].c;
+			else
+			{
+				draworders[dop++]=y*320+(lx=(e[i].x>>16));
+				draworders[dop++]=e[i].c;
+			}
+			vram[(e[i].x>>16)+y*320]=e[i].c;
+			e[i].x+=e[i].dx;
+		}
+		listc=k;
+	}
+}
+
+void	pass1(int *edge)
+{
+	int	dy,y1,y2,x1,x2,a;
+	ec=1; memset(ep,0,200*2);
+	while(*edge!=0x8000)
+	{
+		e[ec].c=edge[0];		
+		y1=edge[3];
+		y2=edge[5];
+		if(y1>y2)
+		{
+			x1=y1; y1=y2; y2=x1; // y1<=>y2
+			x1=edge[4];
+			x2=edge[2];
+		}
+		else
+		{
+			x1=edge[2];
+			x2=edge[4];
+		}
+		e[ec].x1=(long)x1<<16;
+		e[ec].dx=((long)(x2-x1)<<16)/(y2-y1);
+		// if y1<0 clip
+		e[ec].y1=y1;
+		e[ec].y2=y2;
+		if(a=ep[y1])
+		{ // add
+			ep[y1]=ec;
+			e[ec].next=a;
+		}
+		else
+		{ // first
+			ep[y1]=ec;
+			e[ec].next=0;
+		}
+		ec++; 
+		edge+=6;
+	}
+}
+
+main()
+{
+	int	a,b,c,x,y;
+	_setvideomode(_MRES256COLOR);
+	for(a=0;a<60;a++) rand();
+	b=0;
+	for(c=1;c<=4;c<<=1)
+	{
+		x=100+c*10; y=100+c*10;
+		for(a=0;a<8;a++)
+		{
+			edge[b++]=c; // color
+			b++;
+			edge[b++]=x; // X1
+			edge[b++]=y; // Y1
+			x=edge[b++]=rand()%320; // X2
+			y=edge[b++]=rand()%200; // Y2
+		}
+		edge[b++]=c; // color
+		b++;
+		edge[b++]=x; // X1
+		edge[b++]=y; // Y1
+		edge[b++]=100+c*10; // X2
+		edge[b++]=100+c*10; // Y2
+	}
+	edge[b++]=0x8000; // end of list
+	
+	#if 0
+	_setcolor(8);
+	for(b=0;edge[b]!=0x8000;b+=6)
+	{
+		_moveto(edge[b+2],edge[b+3]);
+		_lineto(edge[b+4],edge[b+5]);
+	}
+	#endif
+	pass1(edge);
+	pass2();
+	getch();
+	pass3();
+	getch();
+	_setvideomode(_DEFAULTMODE);
+}