1 /* $Id: fixseg.c,v 1.2 2004-12-19 14:52:48 btb Exp $ */
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17 * Functions to make faces planar and probably other things.
23 static char rcsid[] = "$Id: fixseg.c,v 1.2 2004-12-19 14:52:48 btb Exp $";
37 //#include "segment2.h"
42 #define SWAP(a,b) {temp = (a); (a) = (b); (b) = temp;}
44 // -----------------------------------------------------------------------------------------------------------------
45 // Gauss-Jordan elimination solution of a system of linear equations.
46 // a[1..n][1..n] is the input matrix. b[1..n][1..m] is input containing the m right-hand side vectors.
47 // On output, a is replaced by its matrix inverse and b is replaced by the corresponding set of solution vectors.
48 void gaussj(fix **a, int n, fix **b, int m)
50 int indxc[4], indxr[4], ipiv[4];
51 int i, icol=0, irow=0, j, k, l, ll;
52 fix big, dum, pivinv, temp;
55 mprintf((0,"Error -- array too large in gaussj.\n"));
62 for (i=1; i<=n; i++) {
66 for (k=1; k<=n; k++) {
68 if (abs(a[j][k]) >= big) {
73 } else if (ipiv[k] > 1) {
74 mprintf((0,"Error: Singular matrix-1\n"));
81 // We now have the pivot element, so we interchange rows, if needed, to put the pivot
82 // element on the diagonal. The columns are not physically interchanged, only relabeled:
83 // indxc[i], the column of the ith pivot element, is the ith column that is reduced, while
84 // indxr[i] is the row in which that pivot element was originally located. If indxr[i] !=
85 // indxc[i] there is an implied column interchange. With this form of bookkeeping, the
86 // solution b's will end up in the correct order, and the inverse matrix will be scrambled
91 SWAP(a[irow][l], a[icol][l]);
93 SWAP(b[irow][l], b[icol][l]);
98 if (a[icol][icol] == 0) {
99 mprintf((0,"Error: Singular matrix-2\n"));
102 pivinv = fixdiv(F1_0, a[icol][icol]);
103 a[icol][icol] = F1_0;
106 a[icol][l] = fixmul(a[icol][l], pivinv);
108 b[icol][l] = fixmul(b[icol][l], pivinv);
110 for (ll=1; ll<=n; ll++)
115 a[ll][l] -= a[icol][l]*dum;
117 b[ll][l] -= b[icol][l]*dum;
121 // This is the end of the main loop over columns of the reduction. It only remains to unscramble
122 // the solution in view of the column interchanges. We do this by interchanging pairs of
123 // columns in the reverse order that the permutation was built up.
124 for (l=n; l>=1; l--) {
125 if (indxr[l] != indxc[l])
127 SWAP(a[k][indxr[l]], a[k][indxc[l]]);
133 // -----------------------------------------------------------------------------------------------------------------
134 // Return true if side is planar, else return false.
135 int side_is_planar_p(segment *sp, int side)
138 vms_vector *v0,*v1,*v2,*v3;
141 vp = Side_to_verts[side];
142 v0 = &Vertices[sp->verts[vp[0]]];
143 v1 = &Vertices[sp->verts[vp[1]]];
144 v2 = &Vertices[sp->verts[vp[2]]];
145 v3 = &Vertices[sp->verts[vp[3]]];
147 vm_vec_normalize(vm_vec_normal(&va,v0,v1,v2));
148 vm_vec_normalize(vm_vec_normal(&vb,v0,v2,v3));
150 // If the two vectors are very close to being the same, then generate one quad, else generate two triangles.
151 return (vm_vec_dist(&va,&vb) < F1_0/1000);
154 // -------------------------------------------------------------------------------------------------
155 // Return coordinates of a vertex which is vertex v moved so that all sides of which it is a part become planar.
156 void compute_planar_vert(segment *sp, int side, int v, vms_vector *vp)
158 if ((sp) && (side > -3))
162 // -------------------------------------------------------------------------------------------------
163 // Making Cursegp:Curside planar.
164 // If already planar, return.
165 // for each vertex v on side, not part of another segment
166 // choose the vertex v which can be moved to make all sides of which it is a part planar, minimizing distance moved
167 // if there is no vertex v on side, not part of another segment, give up in disgust
169 // 0 curside made planar (or already was)
170 // 1 did not make curside planar
171 int make_curside_planar(void)
175 vms_vector planar_verts[4]; // store coordinates of up to 4 vertices which will make Curside planar, corresponding to each of 4 vertices on side
176 int present_verts[4]; // set to 1 if vertex is present
178 if (side_is_planar_p(Cursegp, Curside))
181 // Look at all vertices in side to find a free one.
183 present_verts[v] = 0;
185 vp = Side_to_verts[Curside];
187 for (v=0; v<4; v++) {
188 int v1 = vp[v]; // absolute vertex id
189 if (is_free_vertex(Cursegp->verts[v1])) {
190 compute_planar_vert(Cursegp, Curside, Cursegp->verts[v1], &planar_verts[v]);
191 present_verts[v] = 1;
195 // Now, for each v for which present_verts[v] == 1, there is a vector (point) in planar_verts[v].
196 // See which one is closest to the plane defined by the other three points.
197 // Nah...just use the first one we find.
199 if (present_verts[v]) {
200 med_set_vertex(vp[v],&planar_verts[v]);
201 validate_segment(Cursegp);
202 // -- should propagate tmaps to segments or something here...
206 // We tried, but we failed, to make Curside planer.