solvespace/sketch.cpp

#include "solvespace.h"

const hEntity  Entity::FREE_IN_3D = { 0 };
const hEntity  Entity::NO_ENTITY = { 0 };
const hParam   Param::NO_PARAM = { 0 };
#define NO_PARAM (Param::NO_PARAM)

const hGroup Group::HGROUP_REFERENCES = { 1 };
const hRequest Request::HREQUEST_REFERENCE_XY = { 1 };
const hRequest Request::HREQUEST_REFERENCE_YZ = { 2 };
const hRequest Request::HREQUEST_REFERENCE_ZX = { 3 };

#define gs (SS.GW.gs)

void Group::AddParam(IdList<Param,hParam> *param, hParam hp, double v) {
    Param pa;
    memset(&pa, 0, sizeof(pa));
    pa.h = hp;
    pa.val = v;

    param->Add(&pa);
}

void Group::MenuGroup(int id) {
    Group g;
    memset(&g, 0, sizeof(g));
    g.visible = true;

    if(id >= RECENT_IMPORT && id < (RECENT_IMPORT + MAX_RECENT)) {
        strcpy(g.impFile, RecentFile[id-RECENT_IMPORT]);
        id = GraphicsWindow::MNU_GROUP_IMPORT;
    }

    SS.GW.GroupSelection();

    switch(id) {
        case GraphicsWindow::MNU_GROUP_3D:
            g.type = DRAWING_3D;
            g.name.strcpy("draw-in-3d");
            break;

        case GraphicsWindow::MNU_GROUP_WRKPL:
            g.type = DRAWING_WORKPLANE;
            g.name.strcpy("draw-in-plane");
            if(gs.points == 1 && gs.n == 1) {
                g.subtype = WORKPLANE_BY_POINT_ORTHO;

                Vector u = SS.GW.projRight, v = SS.GW.projUp;
                u = u.ClosestOrtho();
                v = v.Minus(u.ScaledBy(v.Dot(u)));
                v = v.ClosestOrtho();

                g.predef.q = Quaternion::From(u, v);
                g.predef.origin = gs.point[0];
            } else if(gs.points == 1 && gs.lineSegments == 2 && gs.n == 3) {
                g.subtype = WORKPLANE_BY_LINE_SEGMENTS;

                g.predef.origin = gs.point[0];
                g.predef.entityB = gs.entity[0];
                g.predef.entityC = gs.entity[1];

                Vector ut = SS.GetEntity(g.predef.entityB)->VectorGetNum();
                Vector vt = SS.GetEntity(g.predef.entityC)->VectorGetNum();
                ut = ut.WithMagnitude(1);
                vt = vt.WithMagnitude(1);

                if(fabs(SS.GW.projUp.Dot(vt)) < fabs(SS.GW.projUp.Dot(ut))) {
                    SWAP(Vector, ut, vt);
                    g.predef.swapUV = true;
                }
                if(SS.GW.projRight.Dot(ut) < 0) g.predef.negateU = true;
                if(SS.GW.projUp.   Dot(vt) < 0) g.predef.negateV = true;
            } else {
                Error("Bad selection for new drawing in workplane.");
                return;
            }
            SS.GW.ClearSelection();
            break;

        case GraphicsWindow::MNU_GROUP_EXTRUDE:
            g.type = EXTRUDE;
            g.opA = SS.GW.activeGroup;
            g.color = RGB(100, 100, 100);
            g.predef.entityB = SS.GW.ActiveWorkplane();
            g.subtype = ONE_SIDED;
            g.name.strcpy("extrude");
            break;

        case GraphicsWindow::MNU_GROUP_ROT: {
            Vector n;
            if(gs.points == 1 && gs.n == 1 && SS.GW.LockedInWorkplane()) {
                g.predef.p = (SS.GetEntity(gs.point[0]))->PointGetNum();
                Entity *w = SS.GetEntity(SS.GW.ActiveWorkplane());
                n = (w->Normal()->NormalN());
                g.activeWorkplane = w->h;
            } else if(gs.points == 1 && gs.vectors == 1 && gs.n == 2) {
                g.predef.p = (SS.GetEntity(gs.point[0]))->PointGetNum();
                n = SS.GetEntity(gs.vector[0])->VectorGetNum();
            } else {
                Error("Bad selection for new rotation.");
                return;
            }
            n = n.WithMagnitude(1);
            g.predef.q = Quaternion::From(0, n.x, n.y, n.z);
            g.type = ROTATE;
            g.opA = SS.GW.activeGroup;
            g.exprA = Expr::From(3)->DeepCopyKeep();
            g.subtype = ONE_SIDED;
            g.name.strcpy("rotate");
            SS.GW.ClearSelection();
            break;
        }

        case GraphicsWindow::MNU_GROUP_TRANS:
            g.type = TRANSLATE;
            g.opA = SS.GW.activeGroup;
            g.exprA = Expr::From(3)->DeepCopyKeep();
            g.subtype = ONE_SIDED;
            g.name.strcpy("translate");
            break;

        case GraphicsWindow::MNU_GROUP_IMPORT: {
            g.type = IMPORTED;
            g.opA = SS.GW.activeGroup;
            if(strlen(g.impFile) == 0) {
                if(!GetOpenFile(g.impFile, SLVS_EXT, SLVS_PATTERN)) return;
            }
            g.name.strcpy("import");
            break;
        }

        default: oops();
    }

    SS.group.AddAndAssignId(&g);
    if(g.type == IMPORTED) {
        SS.ReloadAllImported();
    }
    SS.GenerateAll();
    SS.GW.activeGroup = g.h;
    if(g.type == DRAWING_WORKPLANE) {
        SS.GetGroup(g.h)->activeWorkplane = g.h.entity(0);
    }
    SS.GetGroup(g.h)->Activate();
    SS.GW.AnimateOntoWorkplane();
    TextWindow::ScreenSelectGroup(0, g.h.v);
    SS.TW.Show();
}

char *Group::DescriptionString(void) {
    static char ret[100];
    if(name.str[0]) {
        sprintf(ret, "g%03x-%s", h.v, name.str);
    } else {
        sprintf(ret, "g%03x-(unnamed)", h.v);
    }
    return ret;
}

void Group::Activate(void) {
    if(type == EXTRUDE || type == IMPORTED) {
        SS.GW.showFaces = true;
    } else {
        SS.GW.showFaces = false;
    }
    SS.TW.Show();
}

void Group::Generate(IdList<Entity,hEntity> *entity,
                     IdList<Param,hParam> *param)
{
    Vector gn = (SS.GW.projRight).Cross(SS.GW.projUp);
    Vector gp = SS.GW.projRight.Plus(SS.GW.projUp);
    Vector gc = (SS.GW.offset).ScaledBy(-1);
    gn = gn.WithMagnitude(200/SS.GW.scale);
    gp = gp.WithMagnitude(200/SS.GW.scale);
    int a, i;
    switch(type) {
        case DRAWING_3D:
            break;

        case DRAWING_WORKPLANE: {
            Quaternion q;
            if(subtype == WORKPLANE_BY_LINE_SEGMENTS) {
                Vector u = SS.GetEntity(predef.entityB)->VectorGetNum();
                Vector v = SS.GetEntity(predef.entityC)->VectorGetNum();
                u = u.WithMagnitude(1);
                Vector n = u.Cross(v);
                v = (n.Cross(u)).WithMagnitude(1);

                if(predef.swapUV) SWAP(Vector, u, v);
                if(predef.negateU) u = u.ScaledBy(-1);
                if(predef.negateV) v = v.ScaledBy(-1);
                q = Quaternion::From(u, v);
            } else if(subtype == WORKPLANE_BY_POINT_ORTHO) {
                // Already given, numerically.
                q = predef.q;
            } else oops();

            Entity normal;
            memset(&normal, 0, sizeof(normal));
            normal.type = Entity::NORMAL_N_COPY;
            normal.numNormal = q;
            normal.point[0] = h.entity(2);
            normal.group = h;
            normal.h = h.entity(1);
            entity->Add(&normal);

            Entity point;
            memset(&point, 0, sizeof(point));
            point.type = Entity::POINT_N_COPY;
            point.numPoint = SS.GetEntity(predef.origin)->PointGetNum();
            point.group = h;
            point.h = h.entity(2);
            entity->Add(&point);

            Entity wp;
            memset(&wp, 0, sizeof(wp));
            wp.type = Entity::WORKPLANE;
            wp.normal = normal.h;
            wp.point[0] = point.h;
            wp.group = h;
            wp.h = h.entity(0);
            entity->Add(&wp);
            break;
        }

        case EXTRUDE: {
            AddParam(param, h.param(0), gn.x);
            AddParam(param, h.param(1), gn.y);
            AddParam(param, h.param(2), gn.z);
            int ai, af;
            if(subtype == ONE_SIDED) {
                ai = 0; af = 2;
            } else if(subtype == TWO_SIDED) {
                ai = -1; af = 1;
            } else oops();

            // Get some arbitrary point in the sketch, that will be used
            // as a reference when defining top and bottom faces.
            hEntity pt = { 0 };
            for(i = 0; i < entity->n; i++) {
                Entity *e = &(entity->elem[i]);
                if(e->group.v != opA.v) continue;

                if(e->IsPoint()) pt = e->h;

                e->CalculateNumerical();
                hEntity he = e->h; e = NULL;
                // As soon as I call CopyEntity, e may become invalid! That
                // adds entities, which may cause a realloc.
                CopyEntity(SS.GetEntity(he), ai, REMAP_BOTTOM,
                    h.param(0), h.param(1), h.param(2),
                    NO_PARAM, NO_PARAM, NO_PARAM, NO_PARAM,
                    true, false);
                CopyEntity(SS.GetEntity(he), af, REMAP_TOP,
                    h.param(0), h.param(1), h.param(2),
                    NO_PARAM, NO_PARAM, NO_PARAM, NO_PARAM,
                    true, false);
                MakeExtrusionLines(he);
            }
            // Remapped versions of that arbitrary point will be used to
            // provide points on the plane faces.
            MakeExtrusionTopBottomFaces(pt);
            break;
        }

        case TRANSLATE: {
            // The translation vector
            AddParam(param, h.param(0), gp.x);
            AddParam(param, h.param(1), gp.y);
            AddParam(param, h.param(2), gp.z);

            int n = (int)(exprA->Eval());
            for(a = 0; a < n; a++) {
                for(i = 0; i < entity->n; i++) {
                    Entity *e = &(entity->elem[i]);
                    if(e->group.v != opA.v) continue;

                    e->CalculateNumerical();
                    CopyEntity(e,
                        a*2 - (subtype == ONE_SIDED ? 0 : (n-1)),
                        (a == (n - 1)) ? REMAP_LAST : a,
                        h.param(0), h.param(1), h.param(2),
                        NO_PARAM, NO_PARAM, NO_PARAM, NO_PARAM,
                        true, false);
                }
            }
            break;
        }
        case ROTATE: {
            // The center of rotation
            AddParam(param, h.param(0), gc.x);
            AddParam(param, h.param(1), gc.y);
            AddParam(param, h.param(2), gc.z);
            // The rotation quaternion
            AddParam(param, h.param(3), 15*PI/180);
            AddParam(param, h.param(4), gn.x);
            AddParam(param, h.param(5), gn.y);
            AddParam(param, h.param(6), gn.z);

            int n = (int)(exprA->Eval());
            for(a = 0; a < n; a++) {
                for(i = 0; i < entity->n; i++) {
                    Entity *e = &(entity->elem[i]);
                    if(e->group.v != opA.v) continue;

                    e->CalculateNumerical();
                    CopyEntity(e,
                        a*2 - (subtype == ONE_SIDED ? 0 : (n-1)),
                        (a == (n - 1)) ? REMAP_LAST : a,
                        h.param(0), h.param(1), h.param(2),
                        h.param(3), h.param(4), h.param(5), h.param(6),
                        false, true);
                }
            }
            break;
        }
        case IMPORTED:
            // The translation vector
            AddParam(param, h.param(0), gp.x);
            AddParam(param, h.param(1), gp.y);
            AddParam(param, h.param(2), gp.z);
            // The rotation quaternion
            AddParam(param, h.param(3), 1);
            AddParam(param, h.param(4), 0);
            AddParam(param, h.param(5), 0);
            AddParam(param, h.param(6), 0);
            
            for(i = 0; i < impEntity.n; i++) {
                Entity *ie = &(impEntity.elem[i]);

                CopyEntity(ie, 0, 0,
                    h.param(0), h.param(1), h.param(2),
                    h.param(3), h.param(4), h.param(5), h.param(6),
                    false, false);
            }
            break;

        default: oops();
    }
}

void Group::AddEq(IdList<Equation,hEquation> *l, Expr *expr, int index) {
    Equation eq;
    eq.e = expr;
    eq.h = h.equation(index);
    l->Add(&eq);
}

void Group::GenerateEquations(IdList<Equation,hEquation> *l) {
    Equation eq;
    ZERO(&eq);
    if(type == IMPORTED) {
        // Normalize the quaternion
        ExprQuaternion q = {
            Expr::From(h.param(3)),
            Expr::From(h.param(4)),
            Expr::From(h.param(5)),
            Expr::From(h.param(6)) };
        AddEq(l, (q.Magnitude())->Minus(Expr::From(1)), 0);
    } else if(type == ROTATE) {
        // The axis and center of rotation are specified numerically
#define EC(x) (Expr::From(x))
#define EP(x) (Expr::From(h.param(x)))
        AddEq(l, (EC(predef.p.x))->Minus(EP(0)), 0);
        AddEq(l, (EC(predef.p.y))->Minus(EP(1)), 1);
        AddEq(l, (EC(predef.p.z))->Minus(EP(2)), 2);
        // param 3 is the angle, which is free
        AddEq(l, (EC(predef.q.vx))->Minus(EP(4)), 3);
        AddEq(l, (EC(predef.q.vy))->Minus(EP(5)), 4);
        AddEq(l, (EC(predef.q.vz))->Minus(EP(6)), 5);
    } else if(type == EXTRUDE) {
        if(predef.entityB.v != Entity::FREE_IN_3D.v) {
            // The extrusion path is locked along a line, normal to the
            // specified workplane.
            Entity *w = SS.GetEntity(predef.entityB);
            ExprVector u = w->Normal()->NormalExprsU();
            ExprVector v = w->Normal()->NormalExprsV();
            ExprVector extruden = {
                Expr::From(h.param(0)),
                Expr::From(h.param(1)),
                Expr::From(h.param(2)) };

            AddEq(l, u.Dot(extruden), 0);
            AddEq(l, v.Dot(extruden), 1);
        }
    }
}

hEntity Group::Remap(hEntity in, int copyNumber) {
    int i;
    for(i = 0; i < remap.n; i++) {
        EntityMap *em = &(remap.elem[i]);
        if(em->input.v == in.v && em->copyNumber == copyNumber) {
            // We already have a mapping for this entity.
            return h.entity(em->h.v);
        }
    }
    // We don't have a mapping yet, so create one.
    EntityMap em;
    em.input = in;
    em.copyNumber = copyNumber;
    remap.AddAndAssignId(&em);
    return h.entity(em.h.v);
}

void Group::MakeExtrusionLines(hEntity in) {
    Entity *ep = SS.GetEntity(in);

    Entity en;
    ZERO(&en);
    if(ep->IsPoint()) {
        // A point gets extruded to form a line segment
        en.point[0] = Remap(ep->h, REMAP_TOP);
        en.point[1] = Remap(ep->h, REMAP_BOTTOM);
        en.group = h;
        en.h = Remap(ep->h, REMAP_PT_TO_LINE);
        en.type = Entity::LINE_SEGMENT;
        SS.entity.Add(&en);
    } else if(ep->type == Entity::LINE_SEGMENT) {
        // A line gets extruded to form a plane face; an endpoint of the
        // original line is a point in the plane, and the line is in the plane.
        Vector a = SS.GetEntity(ep->point[0])->PointGetNum();
        Vector b = SS.GetEntity(ep->point[1])->PointGetNum();
        Vector ab = b.Minus(a);

        en.param[0] = h.param(0);
        en.param[1] = h.param(1);
        en.param[2] = h.param(2);
        en.numPoint = a;
        en.numVector = ab;

        en.group = h;
        en.h = Remap(ep->h, REMAP_LINE_TO_FACE);
        en.type = Entity::FACE_XPROD;
        SS.entity.Add(&en);
    }
}

void Group::MakeExtrusionTopBottomFaces(hEntity pt) {
    if(pt.v == 0) return;
    Group *src = SS.GetGroup(opA);
    Vector n = src->poly.normal;

    Entity en;
    ZERO(&en);
    en.type = Entity::FACE_NORMAL_PT;
    en.group = h;

    en.numNormal = Quaternion::From(0, n.x, n.y, n.z);
    en.point[0] = Remap(pt, REMAP_TOP);
    en.h = Remap(Entity::NO_ENTITY, REMAP_TOP);
    SS.entity.Add(&en);

    en.point[0] = Remap(pt, REMAP_BOTTOM);
    en.h = Remap(Entity::NO_ENTITY, REMAP_BOTTOM);
    SS.entity.Add(&en);
}

void Group::CopyEntity(Entity *ep, int timesApplied, int remap,
                       hParam dx, hParam dy, hParam dz,
                       hParam qw, hParam qvx, hParam qvy, hParam qvz,
                       bool asTrans, bool asAxisAngle)
{
    Entity en;
    memset(&en, 0, sizeof(en));
    en.type = ep->type;
    en.h = Remap(ep->h, remap);
    en.timesApplied = timesApplied;
    en.group = h;
    en.construction = ep->construction;

    switch(ep->type) {
        case Entity::WORKPLANE:
            // Don't copy these.
            return;

        case Entity::LINE_SEGMENT:  
            en.point[0] = Remap(ep->point[0], remap);
            en.point[1] = Remap(ep->point[1], remap);
            break;

        case Entity::CUBIC:
            en.point[0] = Remap(ep->point[0], remap);
            en.point[1] = Remap(ep->point[1], remap);
            en.point[2] = Remap(ep->point[2], remap);
            en.point[3] = Remap(ep->point[3], remap);
            break;

        case Entity::CIRCLE:
            en.point[0] = Remap(ep->point[0], remap);
            en.normal   = Remap(ep->normal, remap);
            en.distance = Remap(ep->distance, remap);
            break;

        case Entity::ARC_OF_CIRCLE:
            en.point[0] = Remap(ep->point[0], remap);
            en.point[1] = Remap(ep->point[1], remap);
            en.point[2] = Remap(ep->point[2], remap);
            en.normal   = Remap(ep->normal, remap);
            break;

        case Entity::POINT_N_COPY:
        case Entity::POINT_N_TRANS:
        case Entity::POINT_N_ROT_TRANS:
        case Entity::POINT_N_ROT_AA:
        case Entity::POINT_IN_3D:
        case Entity::POINT_IN_2D:
            if(asTrans) {
                en.type = Entity::POINT_N_TRANS;
                en.param[0] = dx;
                en.param[1] = dy;
                en.param[2] = dz;
            } else {
                if(asAxisAngle) {
                    en.type = Entity::POINT_N_ROT_AA;
                } else {
                    en.type = Entity::POINT_N_ROT_TRANS;
                }
                en.param[0] = dx;
                en.param[1] = dy;
                en.param[2] = dz;
                en.param[3] = qw;
                en.param[4] = qvx;
                en.param[5] = qvy;
                en.param[6] = qvz;
            }
            en.numPoint = ep->actPoint;
            break;

        case Entity::NORMAL_N_COPY:
        case Entity::NORMAL_N_ROT:
        case Entity::NORMAL_N_ROT_AA:
        case Entity::NORMAL_IN_3D:
        case Entity::NORMAL_IN_2D:
            if(asTrans) {
                en.type = Entity::NORMAL_N_COPY;
            } else {
                if(asAxisAngle) {
                    en.type = Entity::NORMAL_N_ROT_AA;
                } else {
                    en.type = Entity::NORMAL_N_ROT;
                }
                en.param[0] = qw;
                en.param[1] = qvx;
                en.param[2] = qvy;
                en.param[3] = qvz;
            }
            en.numNormal = ep->actNormal;
            en.point[0] = Remap(ep->point[0], remap);
            break;

        case Entity::DISTANCE_N_COPY:
        case Entity::DISTANCE:
            en.type = Entity::DISTANCE_N_COPY;
            en.numDistance = ep->actDistance;
            break;

        case Entity::FACE_NORMAL_PT:
        case Entity::FACE_XPROD:
        case Entity::FACE_N_ROT_TRANS:
            if(asTrans || asAxisAngle) return;

            en.type = Entity::FACE_N_ROT_TRANS;
            en.param[0] = dx;
            en.param[1] = dy;
            en.param[2] = dz;
            en.param[3] = qw;
            en.param[4] = qvx;
            en.param[5] = qvy;
            en.param[6] = qvz;
            en.numPoint = ep->numPoint;
            en.numNormal = ep->numNormal;
            break;

        default:
            oops();
    }
    SS.entity.Add(&en);
}

void Group::TagEdgesFromLineSegments(SEdgeList *el) {
    int i, j;
    for(i = 0; i < SS.entity.n; i++) {
        Entity *e = &(SS.entity.elem[i]);
        if(e->group.v != opA.v) continue;
        if(e->type != Entity::LINE_SEGMENT) continue;

        Vector p0 = SS.GetEntity(e->point[0])->PointGetNum();
        Vector p1 = SS.GetEntity(e->point[1])->PointGetNum();
        
        for(j = 0; j < el->l.n; j++) {
            SEdge *se = &(el->l.elem[j]);
            if((p0.Equals(se->a) && p1.Equals(se->b))) se->tag = e->h.v;
            if((p0.Equals(se->b) && p1.Equals(se->a))) se->tag = e->h.v;
        }
    }
}

void Group::GeneratePolygon(void) {
    poly.Clear();

    if(type == DRAWING_3D || type == DRAWING_WORKPLANE || 
       type == ROTATE || type == TRANSLATE)
    {
        SEdgeList edges; ZERO(&edges);
        int i;
        for(i = 0; i < SS.entity.n; i++) {
            Entity *e = &(SS.entity.elem[i]);
            if(e->group.v != h.v) continue;

            e->GenerateEdges(&edges);
        }
        SEdge error;
        if(edges.AssemblePolygon(&poly, &error)) {
            polyError.yes = false;
            poly.normal = poly.ComputeNormal();
            poly.FixContourDirections();
        } else {
            polyError.yes = true;
            polyError.notClosedAt = error;
            poly.Clear();
        }
    }
}

void Group::GenerateMesh(void) {
    SMesh outm;
    ZERO(&outm);
    if(type == EXTRUDE) {
        SEdgeList edges;
        ZERO(&edges);
        int i;
        Group *src = SS.GetGroup(opA);
        Vector translate = Vector::From(h.param(0), h.param(1), h.param(2));

        Vector tbot, ttop;
        if(subtype == ONE_SIDED) {
            tbot = Vector::From(0, 0, 0); ttop = translate.ScaledBy(2);
        } else {
            tbot = translate.ScaledBy(-1); ttop = translate.ScaledBy(1);
        }
        bool flipBottom = translate.Dot(src->poly.normal) > 0;

        // Get a triangulation of the source poly; this is not a closed mesh.
        SMesh srcm; ZERO(&srcm);
        (src->poly).TriangulateInto(&srcm);

        STriMeta meta = { 0, color };

        // Do the bottom; that has normal pointing opposite from translate
        meta.face = Remap(Entity::NO_ENTITY, REMAP_BOTTOM).v;
        for(i = 0; i < srcm.l.n; i++) {
            STriangle *st = &(srcm.l.elem[i]);
            Vector at = (st->a).Plus(tbot), 
                   bt = (st->b).Plus(tbot),
                   ct = (st->c).Plus(tbot);
            if(flipBottom) {
                outm.AddTriangle(meta, ct, bt, at);
            } else {
                outm.AddTriangle(meta, at, bt, ct);
            }
        }
        // And the top; that has the normal pointing the same dir as translate
        meta.face = Remap(Entity::NO_ENTITY, REMAP_TOP).v;
        for(i = 0; i < srcm.l.n; i++) {
            STriangle *st = &(srcm.l.elem[i]);
            Vector at = (st->a).Plus(ttop), 
                   bt = (st->b).Plus(ttop),
                   ct = (st->c).Plus(ttop);
            if(flipBottom) {
                outm.AddTriangle(meta, at, bt, ct);
            } else {
                outm.AddTriangle(meta, ct, bt, at);
            }
        }
        srcm.Clear();
        // Get the source polygon to extrude, and break it down to edges
        edges.Clear();
        (src->poly).MakeEdgesInto(&edges);

        edges.l.ClearTags();
        TagEdgesFromLineSegments(&edges);
        // The sides; these are quads, represented as two triangles.
        for(i = 0; i < edges.l.n; i++) {
            SEdge *edge = &(edges.l.elem[i]);
            Vector abot = (edge->a).Plus(tbot), bbot = (edge->b).Plus(tbot);
            Vector atop = (edge->a).Plus(ttop), btop = (edge->b).Plus(ttop);
            // We tagged the edges that came from line segments; their
            // triangles should be associated with that plane face.
            if(edge->tag) {
                hEntity hl = { edge->tag };
                hEntity hf = Remap(hl, REMAP_LINE_TO_FACE);
                meta.face = hf.v;
            } else {
                meta.face = 0;
            }
            if(flipBottom) {
                outm.AddTriangle(meta, bbot, abot, atop);
                outm.AddTriangle(meta, bbot, atop, btop);
            } else {
                outm.AddTriangle(meta, abot, bbot, atop);
                outm.AddTriangle(meta, bbot, btop, atop);
            }
        }
        edges.Clear();
    } else if(type == IMPORTED) {
        // Triangles are just copied over, with the appropriate transformation
        // applied.
        Vector offset = {
            SS.GetParam(h.param(0))->val,
            SS.GetParam(h.param(1))->val,
            SS.GetParam(h.param(2))->val };
        Quaternion q = {
            SS.GetParam(h.param(3))->val,
            SS.GetParam(h.param(4))->val,
            SS.GetParam(h.param(5))->val,
            SS.GetParam(h.param(6))->val };

        for(int i = 0; i < impMesh.l.n; i++) {
            STriangle st = impMesh.l.elem[i];

            if(st.meta.face != 0) {
                hEntity he = { st.meta.face };
                st.meta.face = Remap(he, 0).v;
            }
            st.a = q.Rotate(st.a).Plus(offset);
            st.b = q.Rotate(st.b).Plus(offset);
            st.c = q.Rotate(st.c).Plus(offset);
            outm.AddTriangle(&st);
        }
    }

    // So our group's mesh appears in outm. Combine this with the previous
    // group's mesh, using the requested operation.
    mesh.Clear();
    SMesh *a = PreviousGroupMesh();
    if(meshCombine == COMBINE_AS_UNION) {
        mesh.MakeFromUnion(a, &outm);
    } else {
        mesh.MakeFromDifference(a, &outm);
    }
    outm.Clear();
}

SMesh *Group::PreviousGroupMesh(void) {
    int i;
    for(i = 0; i < SS.group.n; i++) {
        Group *g = &(SS.group.elem[i]);
        if(g->h.v == h.v) break;
    }
    if(i == 0 || i >= SS.group.n) oops();
    return &(SS.group.elem[i-1].mesh);
}


void Group::Draw(void) {
    // Show this even if the group is not visible. It's already possible
    // to show or hide just this with the "show solids" flag.

    int specColor;
    if(type != EXTRUDE && type != IMPORTED) {
        specColor = RGB(25, 25, 25); // force the color to something dim
    } else {
        specColor = -1; // use the model color
    }
    // The back faces are drawn in red; should never seem them, since we
    // draw closed shells, so that's a debugging aid.
    GLfloat mpb[] = { 1.0f, 0.1f, 0.1f, 1.0 };
    glMaterialfv(GL_BACK, GL_AMBIENT_AND_DIFFUSE, mpb);

    // When we fill the mesh, we need to know which triangles are selected
    // or hovered, in order to draw them differently.
    DWORD mh = 0, ms1 = 0, ms2 = 0;
    hEntity he = SS.GW.hover.entity;
    if(he.v != 0 && SS.GetEntity(he)->IsFace()) {
        mh = he.v;
    }
    SS.GW.GroupSelection();
    if(gs.faces > 0) ms1 = gs.face[0].v;
    if(gs.faces > 1) ms2 = gs.face[1].v;

    glEnable(GL_LIGHTING);
    if(SS.GW.showShaded) glxFillMesh(specColor, &mesh, mh, ms1, ms2);
    glDisable(GL_LIGHTING);

    if(SS.GW.showMesh) glxDebugMesh(&mesh);

    if(!SS.GW.showShaded) return;
    if(polyError.yes) {
        glxColor4d(1, 0, 0, 0.2);
        glLineWidth(10);
        glBegin(GL_LINES);
            glxVertex3v(polyError.notClosedAt.a);
            glxVertex3v(polyError.notClosedAt.b);
        glEnd();
        glLineWidth(1);
        glxColor3d(1, 0, 0);
        glPushMatrix();
            glxTranslatev(polyError.notClosedAt.b);
            glxOntoWorkplane(SS.GW.projRight, SS.GW.projUp);
            glxWriteText("not closed contour!");
        glPopMatrix();
    } else {
        glxColor4d(0, 0.1, 0.1, 0.5);
        glPolygonOffset(-1, -1);
        glxFillPolygon(&poly);
        glPolygonOffset(0, 0);
    }
}

hParam Request::AddParam(IdList<Param,hParam> *param, hParam hp) {
    Param pa;
    memset(&pa, 0, sizeof(pa));
    pa.h = hp;
    param->Add(&pa);
    return hp;
}

void Request::Generate(IdList<Entity,hEntity> *entity,
                       IdList<Param,hParam> *param)
{
    int points = 0;
    int params = 0;
    int et = 0;
    bool hasNormal = false;
    bool hasDistance = false;
    int i;

    Entity e;
    memset(&e, 0, sizeof(e));
    switch(type) {
        case Request::WORKPLANE:
            et = Entity::WORKPLANE;
            points = 1;
            hasNormal = true;
            break;

        case Request::DATUM_POINT:
            et = 0;
            points = 1;
            break;

        case Request::LINE_SEGMENT:
            et = Entity::LINE_SEGMENT;
            points = 2;
            break;

        case Request::CIRCLE:
            et = Entity::CIRCLE;
            points = 1;
            params = 1;
            hasNormal = true;
            hasDistance = true;
            break;

        case Request::ARC_OF_CIRCLE:
            et = Entity::ARC_OF_CIRCLE;
            points = 3;
            hasNormal = true;
            break;

        case Request::CUBIC:
            et = Entity::CUBIC;
            points = 4; 
            break;

        default: oops();
    }

    // Generate the entity that's specific to this request.
    e.type = et;
    e.group = group;
    e.workplane = workplane;
    e.construction = construction;
    e.h = h.entity(0);

    // And generate entities for the points
    for(i = 0; i < points; i++) {
        Entity p;
        memset(&p, 0, sizeof(p));
        p.workplane = workplane;
        // points start from entity 1, except for datum point case
        p.h = h.entity(i+(et ? 1 : 0));
        p.group = group;

        if(workplane.v == Entity::FREE_IN_3D.v) {
            p.type = Entity::POINT_IN_3D;
            // params for x y z
            p.param[0] = AddParam(param, h.param(16 + 3*i + 0));
            p.param[1] = AddParam(param, h.param(16 + 3*i + 1));
            p.param[2] = AddParam(param, h.param(16 + 3*i + 2));
        } else {
            p.type = Entity::POINT_IN_2D;
            // params for u v
            p.param[0] = AddParam(param, h.param(16 + 3*i + 0));
            p.param[1] = AddParam(param, h.param(16 + 3*i + 1));
        }
        entity->Add(&p);
        e.point[i] = p.h;
    }
    if(hasNormal) {
        Entity n;
        memset(&n, 0, sizeof(n));
        n.workplane = workplane;
        n.h = h.entity(32);
        n.group = group;
        if(workplane.v == Entity::FREE_IN_3D.v) {
            n.type = Entity::NORMAL_IN_3D;
            n.param[0] = AddParam(param, h.param(32+0));
            n.param[1] = AddParam(param, h.param(32+1));
            n.param[2] = AddParam(param, h.param(32+2));
            n.param[3] = AddParam(param, h.param(32+3));
        } else {
            n.type = Entity::NORMAL_IN_2D;
            // and this is just a copy of the workplane quaternion,
            // so no params required
        }
        if(points < 1) oops();
        // The point determines where the normal gets displayed on-screen;
        // it's entirely cosmetic.
        n.point[0] = e.point[0];
        entity->Add(&n);
        e.normal = n.h;
    }
    if(hasDistance) {
        Entity d;
        memset(&d, 0, sizeof(d));
        d.workplane = workplane;
        d.h = h.entity(64);
        d.group = group;
        d.type = Entity::DISTANCE;
        d.param[0] = AddParam(param, h.param(64));
        entity->Add(&d);
        e.distance = d.h;
    }
    // And generate any params not associated with the point that
    // we happen to need.
    for(i = 0; i < params; i++) {
        e.param[i] = AddParam(param, h.param(i));
    }

    if(et) entity->Add(&e);
}

char *Request::DescriptionString(void) {
    char *s;
    if(h.v == Request::HREQUEST_REFERENCE_XY.v) {
        s = "#XY";
    } else if(h.v == Request::HREQUEST_REFERENCE_YZ.v) {
        s = "#YZ";
    } else if(h.v == Request::HREQUEST_REFERENCE_ZX.v) {
        s = "#ZX";
    } else {
        switch(type) {
            case WORKPLANE:         s = "workplane"; break;
            case DATUM_POINT:       s = "datum-point"; break;
            case LINE_SEGMENT:      s = "line-segment"; break;
            case CUBIC:             s = "cubic-bezier"; break;
            case CIRCLE:            s = "circle"; break;
            case ARC_OF_CIRCLE:     s = "arc-of-circle"; break;
            default:                s = "???"; break;
        }
    }
    static char ret[100];
    sprintf(ret, "r%03x-%s", h.v, s);
    return ret;
}