shithub: libgraphics

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perform perspective division outside of the raster loop.

also interpolate tangents for each vertex.

--- a/internal.h

+++ b/internal.h

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

 Vertex _dupvertex(Vertex*);

 void _lerpvertex(Vertex*, Vertex*, Vertex*, double);

 void _berpvertex(Vertex*, Vertex*, Vertex*, Vertex*, Point3);

+void _perspdiv(Vertex*, double);

 void _delvattrs(Vertex*);

 void _fprintvattrs(int, Vertex*);

 void _addvattr(Vertexattrs*, char*, int, void*);

--- a/render.c

+++ b/render.c

@@ -307,6 +307,10 @@

 		t.p1 = Pt2(prim->v[1].p.x, prim->v[1].p.y, 1);

 		t.p2 = Pt2(prim->v[2].p.x, prim->v[2].p.y, 1);

+		_perspdiv(prim->v+0, prim->v[0].p.w);

+		_perspdiv(prim->v+1, prim->v[1].p.w);

+		_perspdiv(prim->v+2, prim->v[2].p.w);

+

 		for(p.y = task->wr.min.y; p.y < task->wr.max.y; p.y++)

 		for(p.x = task->wr.min.x; p.x < task->wr.max.x; p.x++){

 			bc = _barycoords(t, Pt2(p.x+0.5,p.y+0.5,1));

@@ -322,9 +326,7 @@

 			pcz = 1.0/(pcz < ε1? ε1: pcz);

 			/* perspective-correct attribute interpolation  */

-			bc = modulapt3(bc, Vec3(prim->v[0].p.w*pcz,

-						prim->v[1].p.w*pcz,

-						prim->v[2].p.w*pcz));

+			bc = mulpt3(bc, pcz);

 			_berpvertex(fsp.v, &prim->v[0], &prim->v[1], &prim->v[2], bc);

 			fsp.p = p;

--- a/vertex.c

+++ b/vertex.c

@@ -57,6 +57,7 @@

 	v->n = lerp3(v0->n, v1->n, t);

 	v->c = lerp3(v0->c, v1->c, t);

 	v->uv = lerp2(v0->uv, v1->uv, t);

+	v->tangent = lerp3(v0->tangent, v1->tangent, t);

 	v->mtl = v0->mtl != nil? v0->mtl: v1->mtl;

 	for(i = 0; i < v0->nattrs; i++){

 		va.id = v0->attrs[i].id;

@@ -82,6 +83,7 @@

 	v->n = berp3(v0->n, v1->n, v2->n, bc);

 	v->c = berp3(v0->c, v1->c, v2->c, bc);

 	v->uv = berp2(v0->uv, v1->uv, v2->uv, bc);

+	v->tangent = berp3(v0->tangent, v1->tangent, v2->tangent, bc);

 	v->mtl = v0->mtl != nil? v0->mtl: v1->mtl != nil? v1->mtl: v2->mtl;

 	for(i = 0; i < v0->nattrs; i++){

 		va.id = v0->attrs[i].id;

@@ -91,6 +93,26 @@

 		else

 			va.n = fberp(v0->attrs[i].n, v1->attrs[i].n, v2->attrs[i].n, bc);

 		addvattr(v, &va);

+	}

+}

+

+/*

+ * perspective divide vertex attributes

+ */

+void

+_perspdiv(Vertex *v, double z⁻¹)

+{

+	Vertexattr *va;

+

+	v->n = mulpt3(v->n, z⁻¹);

+	v->c = mulpt3(v->c, z⁻¹);

+	v->uv = mulpt2(v->uv, z⁻¹);

+	v->tangent = mulpt3(v->tangent, z⁻¹);

+	for(va = v->attrs; va < v->attrs + v->nattrs; va++){

+		if(va->type == VAPoint)

+			va->p = mulpt3(va->p, z⁻¹);

+		else

+			va->n *= z⁻¹;

 	}

 }