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BMesh: decimate improvement for flat surfaces

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Previously decimate on flat areas of a mesh would more or less randomly collapse edges.
(giving bad topology).

This commit includes a topology 'cost', so smaller edges on flat surfaces collapse first.
This commit is contained in:
Campbell Barton
2015-05-21 16:41:08 +10:00
parent 2c000cc9fc
commit aa54d93a29
1 changed files with 32 additions and 0 deletions
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32
source/blender/bmesh/tools/bmesh_decimate_collapse.c
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@@ -47,6 +47,12 @@
#define USE_TRIANGULATE #define USE_TRIANGULATE
#define USE_VERT_NORMAL_INTERP /* has the advantage that flipped faces don't mess up vertex normals */ #define USE_VERT_NORMAL_INTERP /* has the advantage that flipped faces don't mess up vertex normals */
/* if the cost from #BLI_quadric_evaluate is 'noise', fallback to topology */
#define USE_TOPOLOGY_FALLBACK
#ifdef USE_TOPOLOGY_FALLBACK
# define TOPOLOGY_FALLBACK_EPS 1e-6f
#endif
/* these checks are for rare cases that we can't avoid since they are valid meshes still */ /* these checks are for rare cases that we can't avoid since they are valid meshes still */
#define USE_SAFETY_CHECKS #define USE_SAFETY_CHECKS
@@ -196,6 +202,19 @@ static bool bm_edge_collapse_is_degenerate_flip(BMEdge *e, const float optimize_
return false; return false;
} }
#ifdef USE_TOPOLOGY_FALLBACK
/**
* when the cost is so small that its not useful (flat surfaces),
* fallback to using a 'topology' cost.
*
* This avoids cases where a flat (or near flat) areas get very un-even geometry.
*/
static float bm_decim_build_edge_cost_single__topology(BMEdge *e)
{
return fabsf(dot_v3v3(e->v1->no, e->v2->no)) / min_ff(-len_squared_v3v3(e->v1->co, e->v2->co), -FLT_EPSILON);
}
#endif /* USE_TOPOLOGY_FALLBACK */
static void bm_decim_build_edge_cost_single( static void bm_decim_build_edge_cost_single(
BMEdge *e, BMEdge *e,
const Quadric *vquadrics, const float *vweights, const Quadric *vquadrics, const float *vweights,
@@ -266,6 +285,19 @@ static void bm_decim_build_edge_cost_single(
/* note, 'cost' shouldn't be negative but happens sometimes with small values. /* note, 'cost' shouldn't be negative but happens sometimes with small values.
* this can cause faces that make up a flat surface to over-collapse, see [#37121] */ * this can cause faces that make up a flat surface to over-collapse, see [#37121] */
cost = fabsf(cost); cost = fabsf(cost);
#ifdef USE_TOPOLOGY_FALLBACK
if (UNLIKELY(cost < TOPOLOGY_FALLBACK_EPS)) {
/* subtract existing cost to further differentiate edges from one another
*
* keep topology cost below 0.0 so their values don't interfere with quadric cost,
* (and they get handled first).
* */
cost = bm_decim_build_edge_cost_single__topology(e) - cost;
BLI_assert(cost <= 0.0f);
}
#endif
eheap_table[BM_elem_index_get(e)] = BLI_heap_insert(eheap, cost, e); eheap_table[BM_elem_index_get(e)] = BLI_heap_insert(eheap, cost, e);
} }