shithub: libgraphics

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fix line rasterization.

--- a/clip.c

+++ b/clip.c

@@ -53,6 +53,21 @@

 	p->n = 0;

 }

+static void

+fprintpoly(int fd, Polygon *p)

+{

+	int i;

+

+	for(i = 0; i < p->n; i++)

+		fprint(fd, "%d/%lud p %V\n", i, p->n, p->v[i].p);

+}

+

+static int

+eqpt3(Point3 a, Point3 b)

+{

+	return vec3len(subpt3(a, b)) < 1e-6;

+}

+

 /*

  * references:

  * 	- James F. Blinn, Martin E. Newell, “Clipping Using Homogeneous Coordinates”,

@@ -76,9 +91,9 @@

 	double d0, d1, perc;

 	Polygon Vin, Vout;

 	Vertex *v0, *v1, v;	/* edge verts and new vertex (line-plane intersection) */

-	int i, j, nt;

+	int i, j, np;

-	nt = 0;

+	np = 0;

 	memset(&Vin, 0, sizeof Vin);

 	memset(&Vout, 0, sizeof Vout);

 	for(i = 0; i < p[0].type+1; i++)

@@ -119,23 +134,23 @@

 		cleanpoly(&Vout);

 	else switch(p[0].type){

 	case PLine:

-		/* TODO fix line clipping (they disappear instead, why?) */

 		p[0].v[0] = dupvertex(&Vout.v[0]);

-		p[0].v[1] = dupvertex(&Vout.v[1]);

+		p[0].v[1] = eqpt3(Vout.v[0].p, Vout.v[1].p)? dupvertex(&Vout.v[2]): dupvertex(&Vout.v[1]);

 		cleanpoly(&Vout);

+		np = 1;

 		break;

 	case PTriangle:

 		/* triangulate */

-		for(i = 0; i < Vout.n-2; i++, nt++){

+		for(i = 0; i < Vout.n-2; i++, np++){

 			/*

 			 * when performing fan triangulation, indices 0 and 2

 			 * are referenced on every triangle, so duplicate them

 			 * to avoid complications during rasterization.

 			 */

-			memmove(&p[nt], &p[0], sizeof *p);

-			p[nt].v[0] = i < Vout.n-2-1? dupvertex(&Vout.v[0]): Vout.v[0];

-			p[nt].v[1] = Vout.v[i+1];

-			p[nt].v[2] = i < Vout.n-2-1? dupvertex(&Vout.v[i+2]): Vout.v[i+2];

+			memmove(&p[np], &p[0], sizeof *p);

+			p[np].v[0] = i < Vout.n-2-1? dupvertex(&Vout.v[0]): Vout.v[0];

+			p[np].v[1] = Vout.v[i+1];

+			p[np].v[2] = i < Vout.n-2-1? dupvertex(&Vout.v[i+2]): Vout.v[i+2];

 		}

 		break;

 	}

@@ -142,7 +157,7 @@

 	free(Vout.v);

 	free(Vin.v);

-	return nt;

+	return np;

 }

 static int

--- a/render.c

+++ b/render.c

@@ -119,11 +119,12 @@

 			dplen = hypot(dp.x, dp.y);

 			perc = dplen == 0? 0: hypot(Δp.x, Δp.y)/dplen;

-			/* TODO it seems depth testing messes with the output. find out why */

+			if(steep) swapi(&p.x, &p.y);

+

 			z = flerp(prim.v[0].p.z, prim.v[1].p.z, perc);

 			depth = fclamp(z, 0, 1);

-			if(depth <= params->fb->zb[p.x + p.y*Dx(params->fb->r)])

-				continue;

+			if(!ptinrect(p, params->fb->r) || depth <= params->fb->zb[p.x + p.y*Dx(params->fb->r)])

+				goto discard;

 			params->fb->zb[p.x + p.y*Dx(params->fb->r)] = depth;

 			/* interpolate z⁻¹ and get actual z */

@@ -134,8 +135,6 @@

 			perc *= prim.v[0].p.w * z;

 			lerpvertex(&fsp.v, &prim.v[0], &prim.v[1], perc);

-			if(steep) swapi(&p.x, &p.y);

-

 			fsp.p = p;

 			c = params->fshader(&fsp);

 			memfillcolor(params->frag, col2ul(c));

@@ -142,7 +141,7 @@

 			pixel(params->fb->cb, p, params->frag);

 			delvattrs(&fsp.v);

-

+discard:

 			if(steep) swapi(&p.x, &p.y);

 			e += Δe;

--- a/xform.c

+++ b/xform.c

@@ -145,13 +145,12 @@

 	double cotan;

 	cotan = 1/tan(fovy/2);

-	identity3(m);

+	memset(m, 0, 4*4*sizeof(double));

 	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;

-	m[3][3] = 0;

 }

 void