simplify: Add a more verbose tracing mode for edge collapses

This is too noisy for any reasonably sized model but it helps debug
small isolated test cases and unit tests. Ideally we would probably
remove the 'edge eval' (as in a given pass we may evaluate way more
edges than we end up collapsing) but for now since we are not storing
position/attribute errors separately that's the only place where we can
output both errors as well as evaluate bidirectional flips.

Author: zeux

src/simplifier.cpp

@@ -914,7 +914,13 @@ static bool hasTriangleFlips(const EdgeAdjacency& adjacency, const Vector3* vert
 
 		// early-out when at least one triangle flips due to a collapse
 		if (hasTriangleFlip(vertex_positions[a], vertex_positions[b], v0, v1))
+		{
+#if TRACE >= 2
+			printf("edge block %d -> %d: flip welded %d %d %d\n", i0, i1, a, i0, b);
+#endif
+
 			return true;
+		}
 	}
 
 	return false;
@@ -1017,6 +1023,10 @@ static void rankEdgeCollapses(Collapse* collapses, size_t collapse_count, const
 		float ei = quadricError(vertex_quadrics[remap[i0]], vertex_positions[i1]);
 		float ej = quadricError(vertex_quadrics[remap[j0]], vertex_positions[j1]);
 
+#if TRACE >= 2
+		float di = ei, dj = ej;
+#endif
+
 		if (attribute_count)
 		{
 			ei += quadricError(attribute_quadrics[remap[i0]], &attribute_gradients[remap[i0] * attribute_count], attribute_count, vertex_positions[i1], &vertex_attributes[i1 * attribute_count]);
@@ -1027,6 +1037,16 @@ static void rankEdgeCollapses(Collapse* collapses, size_t collapse_count, const
 		c.v0 = ei <= ej ? i0 : j0;
 		c.v1 = ei <= ej ? i1 : j1;
 		c.error = ei <= ej ? ei : ej;
+
+#if TRACE >= 2
+		if (i0 == j0) // c.bidi has been overwritten
+			printf("edge eval %d -> %d: error %f (pos %f, attr %f)\n", c.v0, c.v1,
+				sqrtf(c.error), sqrtf(ei <= ej ? di : dj), sqrtf(ei <= ej ? ei - di : ej - dj));
+		else
+			printf("edge eval %d -> %d: error %f (pos %f, attr %f); reverse %f (pos %f, attr %f)\n", c.v0, c.v1,
+				sqrtf(ei <= ej ? ei : ej), sqrtf(ei <= ej ? di : dj), sqrtf(ei <= ej ? ei - di : ej - dj),
+				sqrtf(ei <= ej ? ej : ei), sqrtf(ei <= ej ? dj : di), sqrtf(ei <= ej ? ej - dj : ei - di));
+#endif
 	}
 }
 
@@ -1126,6 +1146,10 @@ static size_t performEdgeCollapses(unsigned int* collapse_remap, unsigned char*
 			continue;
 		}
 
+#if TRACE >= 2
+		printf("edge commit %d -> %d: kind %d->%d, error %f\n", i0, i1, vertex_kind[i0], vertex_kind[i1], sqrtf(c.error));
+#endif
+
 		assert(collapse_remap[r0] == r0);
 		assert(collapse_remap[r1] == r1);
 
@@ -1673,6 +1697,10 @@ size_t meshopt_simplifyEdge(unsigned int* destination, const unsigned int* indic
 		if (edge_collapse_count == 0)
 			break;
 
+#if TRACE
+		printf("pass %d:%c", int(pass_count++), TRACE >= 2 ? '\n' : ' ');
+#endif
+
 		rankEdgeCollapses(edge_collapses, edge_collapse_count, vertex_positions, vertex_attributes, vertex_quadrics, attribute_quadrics, attribute_gradients, attribute_count, remap);
 
 		sortEdgeCollapses(collapse_order, edge_collapses, edge_collapse_count);
@@ -1684,10 +1712,6 @@ size_t meshopt_simplifyEdge(unsigned int* destination, const unsigned int* indic
 
 		memset(collapse_locked, 0, vertex_count);
 
-#if TRACE
-		printf("pass %d: ", int(pass_count++));
-#endif
-
 		size_t collapses = performEdgeCollapses(collapse_remap, collapse_locked, vertex_quadrics, attribute_quadrics, attribute_gradients, attribute_count, edge_collapses, edge_collapse_count, collapse_order, remap, wedge, vertex_kind, vertex_positions, adjacency, triangle_collapse_goal, error_limit, result_error);
 
 		// no edges can be collapsed any more due to hitting the error limit or triangle collapse limit