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/*
* ***** BEGIN GPL LICENSE BLOCK *****
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* ***** END GPL LICENSE BLOCK *****
*/
/** \file blender/blenlib/intern/polyfill2d_beautify.c
* \ingroup bli
*
* This function is to improve the tessellation resulting from polyfill2d,
* creating optimal topology.
*
* The functionality here matches #BM_mesh_beautify_fill,
* but its far simpler to perform this operation in 2d,
* on a simple polygon representation where we _know_:
*
* - The polygon is primitive with no holes with a continuous boundary.
* - Tris have consistent winding.
* - 2d (saves some hassles projecting face pairs on an axis for every edge-rotation)
* also saves us having to store all previous edge-states (see #EdRotState in bmesh_beautify.c)
*
* \note
*
* No globals - keep threadsafe.
*/
#include "BLI_utildefines.h"
#include "BLI_math.h"
#include "BLI_memarena.h"
#include "BLI_edgehash.h"
#include "BLI_heap.h"
#include "BLI_polyfill2d_beautify.h" /* own include */
#include "BLI_strict_flags.h"
struct PolyEdge {
/** ordered vert indices (smaller first) */
unsigned int verts[2];
/** ordered face indices (depends on winding compared to the edge verts)
* - (verts[0], verts[1]) == faces[0]
* - (verts[1], verts[0]) == faces[1]
*/
unsigned int faces[2];
/**
* The face-index which isn't used by either of the edges verts [0 - 2].
* could be calculated each time, but cleaner to store for reuse.
*/
unsigned int faces_other_v[2];
};
#ifndef NDEBUG
/**
* Only to check for error-cases.
*/
static void polyfill_validate_tri(unsigned int (*tris)[3], unsigned int tri_index, EdgeHash *ehash)
{
const unsigned int *tri = tris[tri_index];
int j_curr;
BLI_assert(!ELEM(tri[0], tri[1], tri[2]) &&
!ELEM(tri[1], tri[0], tri[2]) &&
!ELEM(tri[2], tri[0], tri[1]));
for (j_curr = 0; j_curr < 3; j_curr++) {
struct PolyEdge *e;
unsigned int e_v1 = tri[(j_curr ) ];
unsigned int e_v2 = tri[(j_curr + 1) % 3];
e = BLI_edgehash_lookup(ehash, e_v1, e_v2);
if (e) {
if (e->faces[0] == tri_index) {
BLI_assert(e->verts[0] == e_v1);
BLI_assert(e->verts[1] == e_v2);
}
else if (e->faces[1] == tri_index) {
BLI_assert(e->verts[0] == e_v2);
BLI_assert(e->verts[1] == e_v1);
}
else {
BLI_assert(0);
}
BLI_assert(e->faces[0] != e->faces[1]);
BLI_assert(ELEM(e_v1, UNPACK3(tri)));
BLI_assert(ELEM(e_v2, UNPACK3(tri)));
BLI_assert(ELEM(e_v1, UNPACK2(e->verts)));
BLI_assert(ELEM(e_v2, UNPACK2(e->verts)));
BLI_assert(e_v1 != tris[e->faces[0]][e->faces_other_v[0]]);
BLI_assert(e_v1 != tris[e->faces[1]][e->faces_other_v[1]]);
BLI_assert(e_v2 != tris[e->faces[0]][e->faces_other_v[0]]);
BLI_assert(e_v2 != tris[e->faces[1]][e->faces_other_v[1]]);
BLI_assert(ELEM(tri_index, UNPACK2(e->faces)));
}
}
}
#endif
BLI_INLINE bool is_boundary_edge(unsigned int i_a, unsigned int i_b, const unsigned int coord_last)
{
BLI_assert(i_a < i_b);
return ((i_a + 1 == i_b) || UNLIKELY((i_a == 0) && (i_b == coord_last)));
}
/**
* Assuming we have 2 triangles sharing an edge (2 - 4),
* check if the edge running from (1 - 3) gives better results.
*
* \return (negative number means the edge can be rotated, lager == better).
*/
float BLI_polyfill_beautify_quad_rotate_calc(
const float v1[2], const float v2[2], const float v3[2], const float v4[2])
{
/* not a loop (only to be able to break out) */
do {
bool is_zero_a, is_zero_b;
const float area_2x_234 = cross_tri_v2(v2, v3, v4);
const float area_2x_241 = cross_tri_v2(v2, v4, v1);
const float area_2x_123 = cross_tri_v2(v1, v2, v3);
const float area_2x_134 = cross_tri_v2(v1, v3, v4);
{
BLI_assert((ELEM(v1, v2, v3, v4) == false) &&
(ELEM(v2, v1, v3, v4) == false) &&
(ELEM(v3, v1, v2, v4) == false) &&
(ELEM(v4, v1, v2, v3) == false));
is_zero_a = (fabsf(area_2x_234) <= FLT_EPSILON);
is_zero_b = (fabsf(area_2x_241) <= FLT_EPSILON);
if (is_zero_a && is_zero_b) {
break;
}
}
/* one of the tri's was degenerate, check we're not rotating
* into a different degenerate shape or flipping the face */
if ((fabsf(area_2x_123) <= FLT_EPSILON) || (fabsf(area_2x_134) <= FLT_EPSILON)) {
/* one of the new rotations is degenerate */
break;
}
if ((area_2x_123 >= 0.0f) != (area_2x_134 >= 0.0f)) {
/* rotation would cause flipping */
break;
}
{
/* testing rule: the area divided by the perimeter,
* check if (1-3) beats the existing (2-4) edge rotation */
float area_a, area_b;
float prim_a, prim_b;
float fac_24, fac_13;
float len_12, len_23, len_34, len_41, len_24, len_13;
/* edges around the quad */
len_12 = len_v2v2(v1, v2);
len_23 = len_v2v2(v2, v3);
len_34 = len_v2v2(v3, v4);
len_41 = len_v2v2(v4, v1);
/* edges crossing the quad interior */
len_13 = len_v2v2(v1, v3);
len_24 = len_v2v2(v2, v4);
/* note, area is in fact (area * 2),
* but in this case its OK, since we're comparing ratios */
/* edge (2-4), current state */
area_a = fabsf(area_2x_234);
area_b = fabsf(area_2x_241);
prim_a = len_23 + len_34 + len_24;
prim_b = len_41 + len_12 + len_24;
fac_24 = (area_a / prim_a) + (area_b / prim_b);
/* edge (1-3), new state */
area_a = fabsf(area_2x_123);
area_b = fabsf(area_2x_134);
prim_a = len_12 + len_23 + len_13;
prim_b = len_34 + len_41 + len_13;
fac_13 = (area_a / prim_a) + (area_b / prim_b);
/* negative number if (1-3) is an improved state */
return fac_24 - fac_13;
}
} while (false);
return FLT_MAX;
}
static float polyedge_rotate_beauty_calc(
const float (*coords)[2],
const unsigned int (*tris)[3],
const struct PolyEdge *e)
{
const float *v1, *v2, *v3, *v4;
v1 = coords[tris[e->faces[0]][e->faces_other_v[0]]];
v3 = coords[tris[e->faces[1]][e->faces_other_v[1]]];
v2 = coords[e->verts[0]];
v4 = coords[e->verts[1]];
return BLI_polyfill_beautify_quad_rotate_calc(v1, v2, v3, v4);
}
static void polyedge_beauty_cost_update_single(
const float (*coords)[2],
const unsigned int (*tris)[3],
const struct PolyEdge *edges,
struct PolyEdge *e,
Heap *eheap, HeapNode **eheap_table)
{
const unsigned int i = (unsigned int)(e - edges);
if (eheap_table[i]) {
BLI_heap_remove(eheap, eheap_table[i]);
eheap_table[i] = NULL;
}
{
/* recalculate edge */
const float cost = polyedge_rotate_beauty_calc(coords, tris, e);
/* We can get cases where both choices generate very small negative costs, which leads to infinite loop.
* Anyway, costs above that are not worth recomputing, maybe we could even optimze it to a smaller limit?
* See T43578. */
if (cost < -FLT_EPSILON) {
eheap_table[i] = BLI_heap_insert(eheap, cost, e);
}
else {
eheap_table[i] = NULL;
}
}
}
static void polyedge_beauty_cost_update(
const float (*coords)[2],
const unsigned int (*tris)[3],
const struct PolyEdge *edges,
struct PolyEdge *e,
Heap *eheap, HeapNode **eheap_table,
EdgeHash *ehash)
{
const unsigned int *tri_0 = tris[e->faces[0]];
const unsigned int *tri_1 = tris[e->faces[1]];
unsigned int i;
struct PolyEdge *e_arr[4] = {
BLI_edgehash_lookup(ehash,
tri_0[(e->faces_other_v[0] ) % 3],
tri_0[(e->faces_other_v[0] + 1) % 3]),
BLI_edgehash_lookup(ehash,
tri_0[(e->faces_other_v[0] + 2) % 3],
tri_0[(e->faces_other_v[0] ) % 3]),
BLI_edgehash_lookup(ehash,
tri_1[(e->faces_other_v[1] ) % 3],
tri_1[(e->faces_other_v[1] + 1) % 3]),
BLI_edgehash_lookup(ehash,
tri_1[(e->faces_other_v[1] + 2) % 3],
tri_1[(e->faces_other_v[1] ) % 3]),
};
for (i = 0; i < 4; i++) {
if (e_arr[i]) {
BLI_assert(!(ELEM(e_arr[i]->faces[0], UNPACK2(e->faces)) &&
ELEM(e_arr[i]->faces[1], UNPACK2(e->faces))));
polyedge_beauty_cost_update_single(
coords, tris, edges,
e_arr[i],
eheap, eheap_table);
}
}
}
static void polyedge_rotate(
unsigned int (*tris)[3],
struct PolyEdge *e,
EdgeHash *ehash)
{
unsigned int e_v1_new = tris[e->faces[0]][e->faces_other_v[0]];
unsigned int e_v2_new = tris[e->faces[1]][e->faces_other_v[1]];
#ifndef NDEBUG
polyfill_validate_tri(tris, e->faces[0], ehash);
polyfill_validate_tri(tris, e->faces[1], ehash);
#endif
BLI_assert(e_v1_new != e_v2_new);
BLI_assert(!ELEM(e_v2_new, UNPACK3(tris[e->faces[0]])));
BLI_assert(!ELEM(e_v1_new, UNPACK3(tris[e->faces[1]])));
tris[e->faces[0]][(e->faces_other_v[0] + 1) % 3] = e_v2_new;
tris[e->faces[1]][(e->faces_other_v[1] + 1) % 3] = e_v1_new;
e->faces_other_v[0] = (e->faces_other_v[0] + 2) % 3;
e->faces_other_v[1] = (e->faces_other_v[1] + 2) % 3;
BLI_assert((tris[e->faces[0]][e->faces_other_v[0]] != e_v1_new) &&
(tris[e->faces[0]][e->faces_other_v[0]] != e_v2_new));
BLI_assert((tris[e->faces[1]][e->faces_other_v[1]] != e_v1_new) &&
(tris[e->faces[1]][e->faces_other_v[1]] != e_v2_new));
BLI_edgehash_remove(ehash, e->verts[0], e->verts[1], NULL);
BLI_edgehash_insert(ehash, e_v1_new, e_v2_new, e);
if (e_v1_new < e_v2_new) {
e->verts[0] = e_v1_new;
e->verts[1] = e_v2_new;
}
else {
/* maintain winding info */
e->verts[0] = e_v2_new;
e->verts[1] = e_v1_new;
SWAP(unsigned int, e->faces[0], e->faces[1]);
SWAP(unsigned int, e->faces_other_v[0], e->faces_other_v[1]);
}
/* update adjacent data */
{
unsigned int e_side = 0;
for (e_side = 0; e_side < 2; e_side++) {
/* 't_other' which we need to swap out is always the same edge-order */
const unsigned int t_other = (((e->faces_other_v[e_side]) + 2)) % 3;
unsigned int t_index = e->faces[e_side];
unsigned int t_index_other = e->faces[!e_side];
unsigned int *tri = tris[t_index];
struct PolyEdge *e_other;
unsigned int e_v1 = tri[(t_other ) ];
unsigned int e_v2 = tri[(t_other + 1) % 3];
e_other = BLI_edgehash_lookup(ehash, e_v1, e_v2);
if (e_other) {
BLI_assert(t_index != e_other->faces[0] && t_index != e_other->faces[1]);
if (t_index_other == e_other->faces[0]) {
e_other->faces[0] = t_index;
e_other->faces_other_v[0] = (t_other + 2) % 3;
BLI_assert(!ELEM(tri[e_other->faces_other_v[0]], e_v1, e_v2));
}
else if (t_index_other == e_other->faces[1]) {
e_other->faces[1] = t_index;
e_other->faces_other_v[1] = (t_other + 2) % 3;
BLI_assert(!ELEM(tri[e_other->faces_other_v[1]], e_v1, e_v2));
}
else {
BLI_assert(0);
}
}
}
}
#ifndef NDEBUG
polyfill_validate_tri(tris, e->faces[0], ehash);
polyfill_validate_tri(tris, e->faces[1], ehash);
#endif
BLI_assert(!ELEM(tris[e->faces[0]][e->faces_other_v[0]], UNPACK2(e->verts)));
BLI_assert(!ELEM(tris[e->faces[1]][e->faces_other_v[1]], UNPACK2(e->verts)));
}
/**
* The intention is that this calculates the output of #BLI_polyfill_calc
*
*
* \note assumes the \a coords form a boundary,
* so any edges running along contiguous (wrapped) indices,
* are ignored since the edges wont share 2 faces.
*/
void BLI_polyfill_beautify(
const float (*coords)[2],
const unsigned int coords_tot,
unsigned int (*tris)[3],
/* structs for reuse */
MemArena *arena, Heap *eheap, EdgeHash *ehash)
{
const unsigned int coord_last = coords_tot - 1;
const unsigned int tris_tot = coords_tot - 2;
/* internal edges only (between 2 tris) */
const unsigned int edges_tot = tris_tot - 1;
unsigned int edges_tot_used = 0;
unsigned int i;
HeapNode **eheap_table;
struct PolyEdge *edges = BLI_memarena_alloc(arena, edges_tot * sizeof(*edges));
BLI_assert(BLI_heap_size(eheap) == 0);
BLI_assert(BLI_edgehash_size(ehash) == 0);
/* first build edges */
for (i = 0; i < tris_tot; i++) {
unsigned int j_prev, j_curr, j_next;
j_prev = 2;
j_next = 1;
for (j_curr = 0; j_curr < 3; j_next = j_prev, j_prev = j_curr++) {
int e_index;
unsigned int e_pair[2] = {
tris[i][j_prev],
tris[i][j_curr],
};
if (e_pair[0] > e_pair[1]) {
SWAP(unsigned int, e_pair[0], e_pair[1]);
e_index = 1;
}
else {
e_index = 0;
}
if (!is_boundary_edge(e_pair[0], e_pair[1], coord_last)) {
struct PolyEdge *e = BLI_edgehash_lookup(ehash, e_pair[0], e_pair[1]);
if (e == NULL) {
e = &edges[edges_tot_used++];
BLI_edgehash_insert(ehash, e_pair[0], e_pair[1], e);
memcpy(e->verts, e_pair, sizeof(e->verts));
#ifndef NDEBUG
e->faces[!e_index] = (unsigned int)-1;
#endif
}
else {
/* ensure each edge only ever has 2x users */
#ifndef NDEBUG
BLI_assert(e->faces[e_index] == (unsigned int)-1);
BLI_assert((e->verts[0] == e_pair[0]) &&
(e->verts[1] == e_pair[1]));
#endif
}
e->faces[e_index] = i;
e->faces_other_v[e_index] = j_next;
}
}
}
/* now perform iterative rotations */
eheap_table = BLI_memarena_alloc(arena, sizeof(HeapNode *) * (size_t)edges_tot);
// for (i = 0; i < tris_tot; i++) { polyfill_validate_tri(tris, i, eh); }
/* build heap */
for (i = 0; i < edges_tot; i++) {
struct PolyEdge *e = &edges[i];
const float cost = polyedge_rotate_beauty_calc(coords, (const unsigned int (*)[3])tris, e);
if (cost < 0.0f) {
eheap_table[i] = BLI_heap_insert(eheap, cost, e);
}
else {
eheap_table[i] = NULL;
}
}
while (BLI_heap_is_empty(eheap) == false) {
struct PolyEdge *e = BLI_heap_popmin(eheap);
i = (unsigned int)(e - edges);
eheap_table[i] = NULL;
polyedge_rotate(tris, e, ehash);
/* recalculate faces connected on the heap */
polyedge_beauty_cost_update(
coords, (const unsigned int (*)[3])tris, edges,
e,
eheap, eheap_table, ehash);
}
BLI_heap_clear(eheap, NULL);
BLI_edgehash_clear_ex(ehash, NULL, BLI_POLYFILL_ALLOC_NGON_RESERVE);
/* MEM_freeN(eheap_table); */ /* arena */
}
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