shithub: libgraphics

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fix the barycoords routine to avoid reporting false degenerates.

added a normals buffer for debugging.

--- a/fb.c

+++ b/fb.c

@@ -31,6 +31,17 @@

 }

 static void

+framebufctl_drawnormals(Framebufctl *ctl, Image *dst)

+{

+	Framebuf *fb;

+

+	qlock(ctl);

+	fb = ctl->getfb(ctl);

+	loadimage(dst, rectaddpt(fb->r, dst->r.min), (uchar*)fb->nb, Dx(fb->r)*Dy(fb->r)*4);

+	qunlock(ctl);

+}

+

+static void

 framebufctl_swap(Framebufctl *ctl)

 {

 	qlock(ctl);

@@ -45,6 +56,7 @@

 	/* address the back buffer—resetting the front buffer is VERBOTEN */

 	fb = ctl->getbb(ctl);

+	memset(fb->nb, 0, Dx(fb->r)*Dy(fb->r)*4);

 	memsetd(fb->zb, Inf(-1), Dx(fb->r)*Dy(fb->r));

 	memset(fb->cb, 0, Dx(fb->r)*Dy(fb->r)*4);

 }

@@ -71,6 +83,7 @@

 	fb->cb = emalloc(Dx(r)*Dy(r)*4);

 	fb->zb = emalloc(Dx(r)*Dy(r)*sizeof(*fb->zb));

 	memsetd(fb->zb, Inf(-1), Dx(r)*Dy(r));

+	fb->nb = emalloc(Dx(r)*Dy(r)*4);

 	fb->r = r;

 	return fb;

 }

@@ -94,6 +107,7 @@

 	fc->fb[1] = mkfb(r);

 	fc->draw = framebufctl_draw;

 	fc->memdraw = framebufctl_memdraw;

+	fc->drawnormals = framebufctl_drawnormals;

 	fc->swap = framebufctl_swap;

 	fc->reset = framebufctl_reset;

 	fc->getfb = framebufctl_getfb;

--- a/graphics.h

+++ b/graphics.h

@@ -227,6 +227,7 @@

 {

 	ulong *cb;	/* color buffer */

 	double *zb;	/* z/depth buffer */

+	ulong *nb;	/* normals buffer (DBG only) */

 	Rectangle r;

 };

@@ -238,6 +239,7 @@

 	void (*draw)(Framebufctl*, Image*);

 	void (*memdraw)(Framebufctl*, Memimage*);

+	void (*drawnormals)(Framebufctl*, Image*);

 	void (*swap)(Framebufctl*);

 	void (*reset)(Framebufctl*);

 	Framebuf *(*getfb)(Framebufctl*);

--- a/render.c

+++ b/render.c

@@ -46,6 +46,15 @@

 	dst[Dx(fb->r)*p.y + p.x] = col2ul(c);

 }

+static void

+pixeln(Framebuf *fb, Point p, Color c)

+{

+	ulong *dst;

+

+	dst = fb->nb;

+	dst[Dx(fb->r)*p.y + p.x] = col2ul(c);

+}

+

 static int

 isvisible(Point3 p)

 {

@@ -67,6 +76,21 @@

 	return sa <= 0;

 }

+static Point3

+_barycoords(Triangle2 t, Point2 p)

+{

+	Point2 p0p1 = subpt2(t.p1, t.p0);

+	Point2 p0p2 = subpt2(t.p2, t.p0);

+	Point2 pp0  = subpt2(t.p0, p);

+

+	Point3 v = crossvec3(Vec3(p0p2.x, p0p1.x, pp0.x), Vec3(p0p2.y, p0p1.y, pp0.y));

+

+	/* handle degenerate triangles—i.e. the ones where every point lies on the same line */

+	if(fabs(v.z) < 1e-5)

+		return Pt3(-1,-1,-1,1);

+	return Pt3(1 - (v.x + v.y)/v.z, v.y/v.z, v.x/v.z, 1);

+}

+

 static void

 rasterize(Rastertask *task)

 {

@@ -178,7 +202,7 @@

 		for(p.y = bbox.min.y; p.y < bbox.max.y; p.y++)

 			for(p.x = bbox.min.x; p.x < bbox.max.x; p.x++){

-				bc = barycoords(t, Pt2(p.x,p.y,1));

+				bc = _barycoords(t, Pt2(p.x,p.y,1));

 				if(bc.x < 0 || bc.y < 0 || bc.z < 0)

 					continue;

@@ -198,6 +222,8 @@

 				fsp.p = p;

 				c = params->fshader(&fsp);

 				pixel(params->fb, p, c);

+				fsp.v.n.w = 1;

+				pixeln(params->fb, p, fsp.v.n);

 				delvattrs(&fsp.v);

 			}

 		break;