solvespace/mesh.cpp

#include "solvespace.h"

void SMesh::Clear(void) {
    l.Clear();
}

void SMesh::AddTriangle(STriMeta meta, Vector n, Vector a, Vector b, Vector c) {
    Vector ab = b.Minus(a), bc = c.Minus(b);
    Vector np = ab.Cross(bc);
    if(np.Magnitude() < 1e-10) {
        // ugh; gl sometimes tesselates to collinear triangles
        return;
    }
    if(np.Dot(n) > 0) {
        AddTriangle(meta, a, b, c);
    } else {
        AddTriangle(meta, c, b, a);
    }
}
void SMesh::AddTriangle(STriMeta meta, Vector a, Vector b, Vector c) {
    STriangle t; ZERO(&t);
    t.meta = meta;
    t.a = a;
    t.b = b;
    t.c = c;
    AddTriangle(&t);
}
void SMesh::AddTriangle(STriangle *st) {
    l.Add(st);
}

void SMesh::DoBounding(Vector v, Vector *vmax, Vector *vmin) {
    vmax->x = max(vmax->x, v.x);
    vmax->y = max(vmax->y, v.y);
    vmax->z = max(vmax->z, v.z);

    vmin->x = min(vmin->x, v.x);
    vmin->y = min(vmin->y, v.y);
    vmin->z = min(vmin->z, v.z);
}
void SMesh::GetBounding(Vector *vmax, Vector *vmin) {
    int i;
    *vmin = Vector::From( 1e12,  1e12,  1e12);
    *vmax = Vector::From(-1e12, -1e12, -1e12);
    for(i = 0; i < l.n; i++) {
        STriangle *st = &(l.elem[i]);
        DoBounding(st->a, vmax, vmin);
        DoBounding(st->b, vmax, vmin);
        DoBounding(st->c, vmax, vmin);
    }
}

void SMesh::Simplify(int start) {
#define MAX_TRIANGLES 2000
    if(l.n - start > MAX_TRIANGLES) oops();

    STriMeta meta = l.elem[start].meta;

    STriangle tout[MAX_TRIANGLES];
    int toutc = 0;

    Vector n, conv[MAX_TRIANGLES*3];
    int convc = 0;

    int start0 = start;

    int i, j;
    for(i = start; i < l.n; i++) {
        STriangle *tr = &(l.elem[i]);
        if((tr->Normal()).Magnitude() < LENGTH_EPS*LENGTH_EPS) {
            tr->tag = 0;
        } else {
            tr->tag = 0;
        }
    }

    for(;;) {
        bool didAdd;
        convc = 0;
        for(i = start; i < l.n; i++) {
            STriangle *tr = &(l.elem[i]);
            if(tr->tag) continue;

            tr->tag = 1;
            n = (tr->Normal()).WithMagnitude(1);
            conv[convc++] = tr->a;
            conv[convc++] = tr->b;
            conv[convc++] = tr->c;

            start = i+1;
            break;
        }
        if(i >= l.n) break;

        do {
            didAdd = false;

            for(j = 0; j < convc; j++) {
                Vector a = conv[WRAP((j-1), convc)],
                       b = conv[j], 
                       d = conv[WRAP((j+1), convc)],
                       e = conv[WRAP((j+2), convc)];

                Vector c;
                for(i = start; i < l.n; i++) {
                    STriangle *tr = &(l.elem[i]);
                    if(tr->tag) continue;

                    if((tr->a).Equals(d) && (tr->b).Equals(b)) {
                        c = tr->c;
                    } else if((tr->b).Equals(d) && (tr->c).Equals(b)) {
                        c = tr->a;
                    } else if((tr->c).Equals(d) && (tr->a).Equals(b)) {
                        c = tr->b;
                    } else {
                        continue;
                    }
                    // The vertex at C must be convex; but the others must
                    // be tested
                    Vector ab = b.Minus(a);
                    Vector bc = c.Minus(b);
                    Vector cd = d.Minus(c);
                    Vector de = e.Minus(d);

                    double bDot = (ab.Cross(bc)).Dot(n);
                    double dDot = (cd.Cross(de)).Dot(n);

                    bDot /= min(ab.Magnitude(), bc.Magnitude());
                    dDot /= min(cd.Magnitude(), de.Magnitude());
                   
                    if(fabs(bDot) < LENGTH_EPS && fabs(dDot) < LENGTH_EPS) {
                        conv[WRAP((j+1), convc)] = c;
                        // and remove the vertex at j, which is a dup
                        memmove(conv+j, conv+j+1, 
                                          (convc - j - 1)*sizeof(conv[0]));
                        convc--;
                    } else if(fabs(bDot) < LENGTH_EPS && dDot > 0) {
                        conv[j] = c;
                    } else if(fabs(dDot) < LENGTH_EPS && bDot > 0) {
                        conv[WRAP((j+1), convc)] = c;
                    } else if(bDot > 0 && dDot > 0) {
                        // conv[j] is unchanged, conv[j+1] goes to [j+2]
                        memmove(conv+j+2, conv+j+1,
                                            (convc - j - 1)*sizeof(conv[0]));
                        conv[j+1] = c;
                        convc++;
                    } else {
                        continue;
                    }

                    didAdd = true;
                    tr->tag = 1;
                    break;
                }
            }
        } while(didAdd);

        // I need to debug why this is required; sometimes the above code
        // still generates a convex polygon
        for(i = 0; i < convc; i++) {
            Vector a = conv[WRAP((i-1), convc)],
                   b = conv[i], 
                   c = conv[WRAP((i+1), convc)];
            Vector ab = b.Minus(a);
            Vector bc = c.Minus(b);
            double bDot = (ab.Cross(bc)).Dot(n);
            bDot /= min(ab.Magnitude(), bc.Magnitude());

            if(bDot < 0) oops();
        }

        for(i = 0; i < convc - 2; i++) {
            STriangle tr = STriangle::From(meta, conv[0], conv[i+1], conv[i+2]);
            if((tr.Normal()).Magnitude() > LENGTH_EPS*LENGTH_EPS) {
                tout[toutc++] = tr;
            }
        }
    }

    l.n = start0;
    for(i = 0; i < toutc; i++) {
        AddTriangle(&(tout[i]));
    }
}

void SMesh::AddAgainstBsp(SMesh *srcm, SBsp3 *bsp3) {
    int i;

    for(i = 0; i < srcm->l.n; i++) {
        STriangle *st = &(srcm->l.elem[i]);
        int pn = l.n;
        atLeastOneDiscarded = false;
        bsp3->Insert(st, this);
        if(!atLeastOneDiscarded && (l.n != (pn+1))) {
            l.n = pn;
            if(flipNormal) {
                AddTriangle(st->meta, st->c, st->b, st->a);
            } else {
                AddTriangle(st->meta, st->a, st->b, st->c);
            }
        }
        if(l.n - pn > 1) {
            Simplify(pn);
        }
    }
}

void SMesh::MakeFromUnion(SMesh *a, SMesh *b) {
    SBsp3 *bspa = SBsp3::FromMesh(a);
    SBsp3 *bspb = SBsp3::FromMesh(b);

    flipNormal = false;
    keepCoplanar = false;
    AddAgainstBsp(b, bspa);

    flipNormal = false;
    keepCoplanar = true;
    AddAgainstBsp(a, bspb);
}

void SMesh::MakeFromDifference(SMesh *a, SMesh *b) {
    SBsp3 *bspa = SBsp3::FromMesh(a);
    SBsp3 *bspb = SBsp3::FromMesh(b);

    flipNormal = true;
    keepCoplanar = true;
    AddAgainstBsp(b, bspa);

    flipNormal = false;
    keepCoplanar = false;
    AddAgainstBsp(a, bspb);
}

bool SMesh::MakeFromInterferenceCheck(SMesh *srca, SMesh *srcb, SMesh *error) {
    SBsp3 *bspa = SBsp3::FromMesh(srca);
    SBsp3 *bspb = SBsp3::FromMesh(srcb);

    error->Clear();
    error->flipNormal = true;
    error->keepCoplanar = false;

    error->AddAgainstBsp(srcb, bspa);
    error->AddAgainstBsp(srca, bspb);
    // Now we have a list of all the triangles (or fragments thereof) from
    // A that lie inside B, or vice versa. That's the interference, and
    // we report it so that it can be flagged.
    
    // But as far as the actual model, we just copy everything over.
    int i;
    for(i = 0; i < srca->l.n; i++) {
        AddTriangle(&(srca->l.elem[i]));
    }
    for(i = 0; i < srcb->l.n; i++) {
        AddTriangle(&(srcb->l.elem[i]));
    }
    return (error->l.n == 0);
}

void SMesh::MakeFromCopy(SMesh *a) {
    int i;
    for(i = 0; i < a->l.n; i++) {
        AddTriangle(&(a->l.elem[i]));
    }
}

DWORD SMesh::FirstIntersectionWith(Point2d mp) {
    Vector p0 = Vector::From(mp.x, mp.y, 0);
    Vector gn = Vector::From(0, 0, 1);

    double maxT = -1e12;
    DWORD face = 0;

    int i;
    for(i = 0; i < l.n; i++) {
        STriangle tr = l.elem[i];
        tr.a = SS.GW.ProjectPoint3(tr.a);
        tr.b = SS.GW.ProjectPoint3(tr.b);
        tr.c = SS.GW.ProjectPoint3(tr.c);

        Vector n = tr.Normal();

        if(n.Dot(gn) < LENGTH_EPS) continue; // back-facing or on edge

        if(tr.ContainsPointProjd(gn, p0)) {
            // Let our line have the form r(t) = p0 + gn*t
            double t = -(n.Dot((tr.a).Minus(p0)))/(n.Dot(gn));
            if(t > maxT) {
                maxT = t;
                face = tr.meta.face;
            }
        }
    }
    return face;
}