BMesh: decimate improvement for flat surfaces
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.
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Notes:
blender-bot
2023-02-14 11:20:29 +01:00
Referenced by issue #44794, Blend From Shape tool X Icon UI Bug? Referenced by issue #44780, Decimate Planar generates concave edges
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@ -47,6 +47,12 @@
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#define USE_TRIANGULATE
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#define USE_VERT_NORMAL_INTERP /* has the advantage that flipped faces don't mess up vertex normals */
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/* if the cost from #BLI_quadric_evaluate is 'noise', fallback to topology */
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#define USE_TOPOLOGY_FALLBACK
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#ifdef USE_TOPOLOGY_FALLBACK
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# define TOPOLOGY_FALLBACK_EPS 1e-6f
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#endif
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/* these checks are for rare cases that we can't avoid since they are valid meshes still */
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#define USE_SAFETY_CHECKS
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@ -196,6 +202,19 @@ static bool bm_edge_collapse_is_degenerate_flip(BMEdge *e, const float optimize_
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return false;
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}
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#ifdef USE_TOPOLOGY_FALLBACK
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/**
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* when the cost is so small that its not useful (flat surfaces),
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* fallback to using a 'topology' cost.
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*
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* This avoids cases where a flat (or near flat) areas get very un-even geometry.
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*/
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static float bm_decim_build_edge_cost_single__topology(BMEdge *e)
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{
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return fabsf(dot_v3v3(e->v1->no, e->v2->no)) / min_ff(-len_squared_v3v3(e->v1->co, e->v2->co), -FLT_EPSILON);
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}
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#endif /* USE_TOPOLOGY_FALLBACK */
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static void bm_decim_build_edge_cost_single(
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BMEdge *e,
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const Quadric *vquadrics, const float *vweights,
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@ -266,6 +285,19 @@ static void bm_decim_build_edge_cost_single(
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/* note, 'cost' shouldn't be negative but happens sometimes with small values.
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* this can cause faces that make up a flat surface to over-collapse, see [#37121] */
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cost = fabsf(cost);
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#ifdef USE_TOPOLOGY_FALLBACK
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if (UNLIKELY(cost < TOPOLOGY_FALLBACK_EPS)) {
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/* subtract existing cost to further differentiate edges from one another
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*
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* keep topology cost below 0.0 so their values don't interfere with quadric cost,
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* (and they get handled first).
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* */
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cost = bm_decim_build_edge_cost_single__topology(e) - cost;
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BLI_assert(cost <= 0.0f);
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}
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#endif
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eheap_table[BM_elem_index_get(e)] = BLI_heap_insert(eheap, cost, e);
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}
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