ref: 6c7fd839f6ea6326bae354a27a2ba3c592444856
parent: f2e5828b91c56c2fc0247c5feb5a7215ec4529cc
author: rodri <rgl@antares-labs.eu>
date: Sat Feb 3 17:20:04 EST 2024
document part of the pipeline. prepare the grounds for triangle clipping.
--- a/camera.c
+++ b/camera.c
@@ -43,10 +43,7 @@
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->bz = focus.w == 0? focus: normvec3(subpt3(c->p, focus));
c->bx = normvec3(crossvec3(up, c->bz));
c->by = crossvec3(c->bz, c->bx);
}
--- a/render.c
+++ b/render.c
@@ -98,6 +98,26 @@
return 0;
}
+static int
+cliptriangle(Triangle *)
+{+ /* TODO implement homogeneous clipping procedure */
+
+ /*
+ * requirements:
+ *
+ * - normal and color attributes are carried over to the new
+ * intersecting points without modification.
+ * - uv coordinates must be adjusted in proportion to the new
+ * points.
+ */
+ return 1;
+}
+
+/*
+ * transforms p from the world reference frame
+ * to c's one (aka Viewing Coordinate System).
+ */
Point3
world2vcs(Camera *c, Point3 p)
{@@ -104,6 +124,19 @@
return rframexform3(p, *c);
}
+/*
+ * projects p from the VCS to clip space, placing
+ * p.[xyz] ∈ (-∞,-w)∪[-w,w]∪(w,∞) where [-w,w]
+ * represents the visibility volume.
+ *
+ * the clipping planes are:
+ *
+ * | -w | w |
+ * +----------------+
+ * | left | right |
+ * | bottom | top |
+ * | far | near |
+ */
Point3
vcs2clip(Camera *c, Point3 p)
{@@ -116,6 +149,11 @@
return vcs2clip(c, world2vcs(c, p));
}
+/*
+ * performs the perspective division, placing
+ * p.[xyz] ∈ [-1,1] and p.w = 1
+ * (aka Normalized Device Coordinates).
+ */
static Point3
clip2ndc(Point3 p)
{@@ -122,6 +160,11 @@
return divpt3(p, p.w);
}
+/*
+ * scales p to fit the destination viewport,
+ * placing p.x ∈ [0,width], p.y ∈ [0,height],
+ * p.z ∈ [0,1] and leaving p.w intact.
+ */
static Point3
ndc2viewport(Framebuf *fb, Point3 p)
{@@ -240,8 +283,9 @@
OBJVertex *verts, *tverts, *nverts; /* geometric, texture and normals vertices */
OBJIndexArray *idxtab;
OBJElem **ep;
- Triangle t;
Point3 n; /* surface normal */
+ Triangle t[2*3]; /* triangles to raster */
+ int nt;
params = arg;
vsp.su = params;
@@ -254,52 +298,56 @@
nverts = params->model->vertdata[OBJVNormal].verts;
for(ep = params->b; ep != params->e; ep++){+ nt = 1; /* start with one. after clipping it might change */
+
idxtab = &(*ep)->indextab[OBJVGeometric];
+ t[0][0].p = Pt3(verts[idxtab->indices[0]].x,verts[idxtab->indices[0]].y,verts[idxtab->indices[0]].z,verts[idxtab->indices[0]].w);
+ t[0][1].p = Pt3(verts[idxtab->indices[1]].x,verts[idxtab->indices[1]].y,verts[idxtab->indices[1]].z,verts[idxtab->indices[1]].w);
+ t[0][2].p = Pt3(verts[idxtab->indices[2]].x,verts[idxtab->indices[2]].y,verts[idxtab->indices[2]].z,verts[idxtab->indices[2]].w);
- t[0].p = Pt3(verts[idxtab->indices[0]].x,verts[idxtab->indices[0]].y,verts[idxtab->indices[0]].z,verts[idxtab->indices[0]].w);
- t[1].p = Pt3(verts[idxtab->indices[1]].x,verts[idxtab->indices[1]].y,verts[idxtab->indices[1]].z,verts[idxtab->indices[1]].w);
- t[2].p = Pt3(verts[idxtab->indices[2]].x,verts[idxtab->indices[2]].y,verts[idxtab->indices[2]].z,verts[idxtab->indices[2]].w);
-
idxtab = &(*ep)->indextab[OBJVNormal];
if(idxtab->nindex == 3){- t[0].n = Vec3(nverts[idxtab->indices[0]].i, nverts[idxtab->indices[0]].j, nverts[idxtab->indices[0]].k);
- t[0].n = normvec3(t[0].n);
- t[1].n = Vec3(nverts[idxtab->indices[1]].i, nverts[idxtab->indices[1]].j, nverts[idxtab->indices[1]].k);
- t[1].n = normvec3(t[1].n);
- t[2].n = Vec3(nverts[idxtab->indices[2]].i, nverts[idxtab->indices[2]].j, nverts[idxtab->indices[2]].k);
- t[2].n = normvec3(t[2].n);
+ t[0][0].n = Vec3(nverts[idxtab->indices[0]].i, nverts[idxtab->indices[0]].j, nverts[idxtab->indices[0]].k);
+ t[0][0].n = normvec3(t[0][0].n);
+ t[0][1].n = Vec3(nverts[idxtab->indices[1]].i, nverts[idxtab->indices[1]].j, nverts[idxtab->indices[1]].k);
+ t[0][1].n = normvec3(t[0][1].n);
+ t[0][2].n = Vec3(nverts[idxtab->indices[2]].i, nverts[idxtab->indices[2]].j, nverts[idxtab->indices[2]].k);
+ t[0][2].n = normvec3(t[0][2].n);
}else{- n = normvec3(crossvec3(subpt3(t[2].p, t[0].p), subpt3(t[1].p, t[0].p)));
- t[0].n = t[1].n = t[2].n = mulpt3(n, -1);
+ /* TODO build a list of per-vertex normals earlier */
+ n = normvec3(crossvec3(subpt3(t[0][2].p, t[0][0].p), subpt3(t[0][1].p, t[0][0].p)));
+ t[0][0].n = t[0][1].n = t[0][2].n = mulpt3(n, -1);
}
- vsp.v = &t[0];
+ idxtab = &(*ep)->indextab[OBJVTexture];
+ if(params->modeltex != nil && idxtab->nindex == 3){+ t[0][0].uv = Pt2(tverts[idxtab->indices[0]].u, tverts[idxtab->indices[0]].v, 1);
+ t[0][1].uv = Pt2(tverts[idxtab->indices[1]].u, tverts[idxtab->indices[1]].v, 1);
+ t[0][2].uv = Pt2(tverts[idxtab->indices[2]].u, tverts[idxtab->indices[2]].v, 1);
+ }else{+ t[0][0].uv = t[0][1].uv = t[0][2].uv = Vec2(0,0);
+ }
+
+ vsp.v = &t[0][0];
vsp.idx = 0;
- t[0].p = params->vshader(&vsp);
- vsp.v = &t[1];
+ t[0][0].p = params->vshader(&vsp);
+ vsp.v = &t[0][1];
vsp.idx = 1;
- t[1].p = params->vshader(&vsp);
- vsp.v = &t[2];
+ t[0][1].p = params->vshader(&vsp);
+ vsp.v = &t[0][2];
vsp.idx = 2;
- t[2].p = params->vshader(&vsp);
+ t[0][2].p = params->vshader(&vsp);
-// if(isclipping(t[0].p) || isclipping(t[1].p) || isclipping(t[2].p))
-// continue; /* TODO clip the primitive */
+ if(isclipping(t[0][0].p) || isclipping(t[0][1].p) || isclipping(t[0][2].p))
+ nt = cliptriangle(t);
- t[0].p = ndc2viewport(params->fb, clip2ndc(t[0].p));
- t[1].p = ndc2viewport(params->fb, clip2ndc(t[1].p));
- t[2].p = ndc2viewport(params->fb, clip2ndc(t[2].p));
+ while(nt--){+ t[nt][0].p = ndc2viewport(params->fb, clip2ndc(t[nt][0].p));
+ t[nt][1].p = ndc2viewport(params->fb, clip2ndc(t[nt][1].p));
+ t[nt][2].p = ndc2viewport(params->fb, clip2ndc(t[nt][2].p));
- idxtab = &(*ep)->indextab[OBJVTexture];
- if(params->modeltex != nil && idxtab->nindex == 3){- t[0].uv = Pt2(tverts[idxtab->indices[0]].u, tverts[idxtab->indices[0]].v, 1);
- t[1].uv = Pt2(tverts[idxtab->indices[1]].u, tverts[idxtab->indices[1]].v, 1);
- t[2].uv = Pt2(tverts[idxtab->indices[2]].u, tverts[idxtab->indices[2]].v, 1);
- }else{- t[0].uv = t[1].uv = t[2].uv = Vec2(0,0);
+ rasterize(params, t[nt], frag);
}
-
- rasterize(params, t, frag);
}
freememimage(frag);