Commit: aa54d93a29b3ed8525670ddb76b2d86ef091142e
Author: Campbell Barton
Date: Thu May 21 16:41:08 2015 +1000
Branches: master
https://developer.blender.org/rBaa54d93a29b3ed8525670ddb76b2d86ef091142e
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.
===================================================================
M source/blender/bmesh/tools/bmesh_decimate_collapse.c
===================================================================
diff --git a/source/blender/bmesh/tools/bmesh_decimate_collapse.c
b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
index a265784..fafd4c5 100644
--- a/source/blender/bmesh/tools/bmesh_decimate_collapse.c
+++ b/source/blender/bmesh/tools/bmesh_decimate_collapse.c
@@ -47,6 +47,12 @@
#define USE_TRIANGULATE
#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 */
#define USE_SAFETY_CHECKS
@@ -196,6 +202,19 @@ static bool bm_edge_collapse_is_degenerate_flip(BMEdge *e,
const float optimize_
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(
BMEdge *e,
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.
* this can cause faces that make up a flat surface to over-collapse,
see [#37121] */
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);
}
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