ref: f28701a4f6b817d1e5b325eb81ed4892ebecacbf
parent: 13a97ea9716bf0c7fa516ffa4adc3b119b964e7b
author: qwx <qwx@sciops.net>
date: Fri Mar 12 06:45:05 EST 2021
add 3d06: clipping
--- /dev/null
+++ b/3d06.c
@@ -1,0 +1,224 @@
+/* global map + transformed map + perspective,
+ * floating point coordinates */
+
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include "dat.h"
+#include "fns.h"
+
+enum{+ Hz = 30,
+};
+char *progname = "3d05";
+
+int tdiv = Te3 / Hz;
+
+enum{+ Cbg,
+ Cplayer,
+ Carrow,
+ Cwall,
+ Cside,
+ Cend,
+};
+static Image *col[Cend];
+
+typedef struct Player Player;
+struct Player{+ Foint;
+ double θ;
+};
+static Player player;
+static Fectangle wall;
+
+static double
+crossprod(Foint a, Foint b)
+{+ return a.x * b.y - a.y * b.x; /* = z */
+}
+
+static Foint
+intersect(Foint p0, Foint p1, Foint p2, Foint p3)
+{+ double x, y, det;
+
+ x = crossprod(p0, p1);
+ y = crossprod(p2, p3);
+ det = crossprod(Ft(p0.x - p1.x, p0.y - p1.y), Ft(p2.x - p3.x, p2.y - p2.y));
+ if(det == 0.0)
+ det = 1e-9;
+ x = crossprod(Ft(x, p0.x - p1.x), Ft(y, p2.x - p3.x)) / det;
+ y = crossprod(Ft(x, p0.y - p1.y), Ft(y, p2.y - p3.y)) / det;
+ return (Foint){x, y};+}
+
+static void
+forward(void)
+{+ player.x += cos(player.θ);
+ player.y += sin(player.θ);
+}
+
+static void
+backward(void)
+{+ player.x -= cos(player.θ);
+ player.y -= sin(player.θ);
+}
+
+static void
+turnleft(void)
+{+ player.θ -= 0.1;
+}
+
+static void
+turnright(void)
+{+ player.θ += 0.1;
+}
+
+static void
+transleft(void)
+{+ player.x += sin(player.θ);
+ player.y -= cos(player.θ);
+}
+
+static void
+transright(void)
+{+ player.x -= sin(player.θ);
+ player.y += cos(player.θ);
+}
+
+Key keys[] = {+ {'w', forward},+ {'s', backward},+ {'a', turnleft},+ {'d', turnright},+ {'q', transleft},+ {'e', transright},+};
+int nkeys = nelem(keys);
+
+static void
+stepsim(void)
+{+ Key *k;
+
+ for(k=keys; k<keys+nkeys; k++)
+ if(k->down)
+ k->fn();
+}
+
+static void
+render(void)
+{+ Player pl;
+ Foint z1, z2;
+ Fectangle r, wl, rwl;
+ Rectangle top, bottom;
+
+ draw(fb, fb->r, col[Cbg], nil, ZP);
+ wl = wall;
+ pl = player;
+
+ /* absolute map */
+ line(fb, PFt(wl.min), PFt(wl.max), 0, 0, 1, col[Cwall], ZP);
+ ellipse(fb, Pt(pl.x, pl.y), 2, 2, 0, col[Cplayer], ZP);
+ line(fb, Pt(pl.x, pl.y),
+ Pt(pl.x + cos(player.θ) * 15, pl.y + sin(player.θ) * 15),
+ 0, 0, 0, col[Carrow], ZP);
+
+ /* transform vertices relative to player coordinates */
+ wl.min.x -= pl.x;
+ wl.min.y -= pl.y;
+ wl.max.x -= pl.x;
+ wl.max.y -= pl.y;
+ rwl.min.x = wl.min.x * sin(player.θ) - wl.min.y * cos(player.θ);
+ rwl.min.y = wl.min.x * cos(player.θ) + wl.min.y * sin(player.θ); /* now left depth (since camera looks towards -∞ along y axis */
+ rwl.max.x = wl.max.x * sin(player.θ) - wl.max.y * cos(player.θ);
+ rwl.max.y = wl.max.x * cos(player.θ) + wl.max.y * sin(player.θ); /* now right depth */
+ /* offset view */
+ pl.x = 200;
+ pl.y = 50;
+ r.min.x = pl.x - rwl.min.x;
+ r.min.y = pl.y - rwl.min.y;
+ r.max.x = pl.x - rwl.max.x;
+ r.max.y = pl.y - rwl.max.y;
+ line(fb, PFt(r.min), PFt(r.max), 0, 0, 1, col[Cwall], ZP);
+ ellipse(fb, Pt(pl.x, pl.y), 2, 2, 0, col[Cplayer], ZP);
+ line(fb, Pt(pl.x, pl.y),
+ Pt(pl.x + cos(-PI/2) * 15, pl.y + sin(-PI/2) * 15),
+ 0, 0, 0, col[Carrow], ZP);
+
+ /* perspective-transformed map:
+ * just take the transformed wall coordinates and divide by depth */
+ /* first clip line if it crosses the player's viewplane,
+ * ie. when one of the depth coordinates is negative;
+ * if both are negative, it is behind the player */
+ if(rwl.min.y <= 0 && rwl.max.y <= 0)
+ return;
+ if(rwl.min.y == 0)
+ rwl.min.y = 1;
+ if(rwl.max.y == 0)
+ rwl.max.y = 1;
+ z1 = intersect(Ft(rwl.min.x, rwl.min.y), Ft(rwl.max.x, rwl.max.y), Ft(-1e-4, 1e-4), Ft(-20, 5));
+ z2 = intersect(Ft(rwl.min.x, rwl.min.y), Ft(rwl.max.x, rwl.max.y), Ft(1e-4, 1e-4), Ft(20, 5));
+ if(rwl.min.y <= 0){+ if(z1.y > 0)
+ rwl.min.x = z1.x, rwl.min.y = z1.y;
+ else
+ rwl.min.x = z2.x, rwl.min.y = z2.y;
+ }
+ if(rwl.max.y <= 0){+ if(z1.y > 0)
+ rwl.max.x = z1.x, rwl.max.y = z1.y;
+ else
+ rwl.max.x = z2.x, rwl.max.y = z2.y;
+ }
+ /* length of the wall = 50 (euclidean distance), we divide for smaller viewsize */
+ top.min.x = 50 - rwl.min.x * 50/2 / rwl.min.y;
+ top.max.x = 50 - rwl.max.x * 50/2 / rwl.max.y;
+ top.min.y = 50 + -50 / rwl.min.y;
+ top.max.y = 50 + -50 / rwl.max.y;
+ bottom.min.x = top.min.x;
+ bottom.max.x = top.max.x;
+ bottom.min.y = 50 + 50 / rwl.min.y;
+ bottom.max.y = 50 + 50 / rwl.max.y;
+ /* offset view */
+ pl.x = 300;
+ top = rectaddpt(top, Pt(pl.x, pl.y));
+ bottom = rectaddpt(bottom, Pt(pl.x, pl.y));
+ line(fb, top.min, top.max, 0, 0, 1, col[Cwall], ZP);
+ line(fb, bottom.min, bottom.max, 0, 0, 1, col[Cwall], ZP);
+ line(fb, top.min, bottom.min, 0, 0, 1, col[Cside], ZP);
+ line(fb, top.max, bottom.max, 0, 0, 1, col[Cside], ZP);
+}
+
+static void
+initrender(void)
+{+ col[Cbg] = display->black;
+ col[Cplayer] = display->white;
+ col[Carrow] = eallocimage(Rect(0,0,1,1), screen->chan, 1, 0x777777ff);
+ col[Cwall] = eallocimage(Rect(0,0,1,1), screen->chan, 1, DYellow);
+ col[Cside] = eallocimage(Rect(0,0,1,1), screen->chan, 1, DRed);
+}
+
+static void
+initsim(void)
+{+ wall = (Fectangle){(Foint){70, 20}, (Foint){70, 70}};+ player = (Player){(Foint){50, 50}, 0};+}
+
+void
+threadmain(int, char**)
+{+ sysinit(initrender, initsim, render, stepsim);
+ sim();
+}
--- a/drw.c
+++ b/drw.c
@@ -26,6 +26,12 @@
return (Point){p.x, p.y};}
+Foint
+Ft(double x, double y)
+{+ return (Foint){x, y};+}
+
Rectangle
RFect(Fectangle r)
{--- a/fns.h
+++ b/fns.h
@@ -4,6 +4,7 @@
Image* eallocimage(Rectangle, ulong, int, ulong);
Point PFt(Foint);
Rectangle RFect(Fectangle);
+Foint Ft(double, double);
void updatedraw(void);
void redraw(void);
void resetdraw(void);
--- a/mkfile
+++ b/mkfile
@@ -5,6 +5,7 @@
3d03\
3d04\
3d05\
+ 3d06\
OFILES=\
drw.$O\