From 0373255087377122eeb10e006ffb8aa1b57e611c Mon Sep 17 00:00:00 2001
From: rgl <devnull@localhost>
Date: Mon, 3 Feb 2020 22:42:28 +0100
Subject: after a year or so of work, i dare create a proper repo.

---
 libgraphics/camera.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 libgraphics/camera.c

(limited to 'libgraphics/camera.c')

diff --git a/libgraphics/camera.c b/libgraphics/camera.c
new file mode 100644
index 0000000..c850477
--- /dev/null
+++ b/libgraphics/camera.c
@@ -0,0 +1,103 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include "../geometry.h"
+#include "../graphics.h"
+
+static int
+max(int a, int b)
+{
+	return a > b ? a : b;
+}
+
+static void
+verifycfg(Camera *c)
+{
+	assert(c->viewport != nil);
+	if(c->ptype == Ppersp)
+		assert(c->fov >= 1 && c->fov < 360);
+	assert(c->clip.n > 0 && c->clip.n < c->clip.f);
+}
+
+void
+perspective(Matrix3 m, double fov, double a, double n, double f)
+{
+	double cotan;
+
+	cotan = 1/tan(fov/2*DEG);
+	identity3(m);
+	m[0][0] =  cotan/a;
+	m[1][1] =  cotan;
+	m[2][2] = -(f+n)/(f-n);
+	m[2][3] = -2*f*n/(f-n);
+	m[3][2] = -1;
+}
+
+void
+orthographic(Matrix3 m, double l, double r, double b, double t, double n, double f)
+{
+	identity3(m);
+	m[0][0] =  2/(r - l);
+	m[1][1] =  2/(t - b);
+	m[2][2] = -2/(f - n);
+	m[0][3] = -(r + l)/(r - l);
+	m[1][3] = -(t + b)/(t - b);
+	m[2][3] = -(f + n)/(f - n);
+}
+
+void
+configcamera(Camera *c, Image *v, double fov, double n, double f, Projection p)
+{
+	c->viewport = v;
+	c->fov = fov;
+	c->clip.n = n;
+	c->clip.f = f;
+	c->ptype = p;
+	reloadcamera(c);
+}
+
+void
+placecamera(Camera *c, Point3 p, Point3 focus, Point3 up)
+{
+	c->p = p;
+	if(focus.w == 0)
+		c->bz = focus;
+	else
+		c->bz = normvec3(subpt3(c->p, focus));
+	c->bx = normvec3(crossvec3(up, c->bz));
+	c->by = crossvec3(c->bz, c->bx);
+}
+
+void
+aimcamera(Camera *c, Point3 focus)
+{
+	placecamera(c, c->p, focus, c->by);
+}
+
+void
+reloadcamera(Camera *c)
+{
+	double a;
+	double l, r, b, t;
+
+	verifycfg(c);
+	switch(c->ptype){
+	case Portho:
+		/*
+		r = Dx(c->viewport->r)/2;
+		t = Dy(c->viewport->r)/2;
+		l = -r;
+		b = -t;
+		*/
+		l = t = 0;
+		r = Dx(c->viewport->r);
+		b = Dy(c->viewport->r);
+		orthographic(c->proj, l, r, b, t, c->clip.n, c->clip.f);
+		break;
+	case Ppersp:
+		a = (double)Dx(c->viewport->r)/Dy(c->viewport->r);
+		perspective(c->proj, c->fov, a, c->clip.n, c->clip.f);
+		break;
+	default: sysfatal("unknown projection type");
+	}
+}
-- 
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