simplify hulls in dual space

src/bounce/collision/shapes/qhull.cpp

@@ -176,8 +176,102 @@ void b3QHull::Set(const b3Vec3* points, u32 count)
 	}
 
 	// Create a convex hull.
+	qhHull primary;
+	primary.Construct(ps, psCount);
+
+	// Simplify the constructed hull.
+
+	// Put the origin inside the hull.
+	b3Vec3 s;
+	s.SetZero();
+	for (qhVertex* v = primary.GetVertexList().head; v; v = v->next)
+	{
+		s += v->position;
+	}
+	s /= float32(primary.GetVertexList().count);
+
+	primary.Translate(-s);
+
+	// Build the dual hull 
+	u32 dvCount = 0;
+	qhFace** dfs = (qhFace**)b3Alloc(primary.GetFaceList().count * sizeof(qhFace*));
+	b3Vec3* dvs = (b3Vec3*)b3Alloc(primary.GetFaceList().count * sizeof(b3Vec3));
+
+	for (qhFace* f = primary.GetFaceList().head; f; f = f->next)
+	{
+		b3Plane plane = f->plane;
+		B3_ASSERT(plane.offset > 0.0f);
+		b3Vec3 v = plane.normal / plane.offset;
+
+		bool unique = true;
+
+		// There's a magic portion of code lost in the island that would cluster those planes.
+		// While we can't find it, simply keep the face which has the largest area.
+		for (u32 j = 0; j < dvCount; ++j)
+		{
+			qhFace*& df = dfs[j];
+			b3Vec3& dv = dvs[j];
+
+			const float32 kTol = 0.1f;
+			if (b3DistanceSquared(v, dv) <= kTol)
+			{
+				if (f->area > df->area)
+				{
+					df = f;
+					dv = v;
+				}
+
+				unique = false;
+				break;
+			}
+		}
+
+		if (unique)
+		{
+			dfs[dvCount] = f;
+			dvs[dvCount] = v;
+			++dvCount;
+		}
+	}
+
+	b3Free(dfs);
+
+	qhHull dual;
+	dual.Construct(dvs, dvCount);
+	b3Free(dvs);
+
+	// Recover the simplified hull in primary space. 
+	u32 pvCount = 0;
+	b3Vec3* pvs = (b3Vec3*)b3Alloc(dual.GetFaceList().count * sizeof(b3Vec3));
+	for (qhFace* f = dual.GetFaceList().head; f; f = f->next)
+	{
+		b3Plane plane = f->plane;
+		B3_ASSERT(plane.offset > 0.0f);
+		b3Vec3 v = plane.normal / plane.offset;
+
+		bool unique = true;
+
+		for (u32 j = 0; j < pvCount; ++j)
+		{
+			if (b3DistanceSquared(v, pvs[j]) <= B3_LINEAR_SLOP * B3_LINEAR_SLOP)
+			{
+				unique = false;
+				break;
+			}
+		}
+
+		if (unique)
+		{
+			pvs[pvCount++] = v;
+		}
+	}
+
 	qhHull hull;
-	hull.Construct(ps, psCount);
+	hull.Construct(pvs, pvCount);
+	b3Free(pvs);
+
+	// Translate the hull back to the origin
+	hull.Translate(s);
 
 	if (hull.GetVertexList().count > B3_MAX_HULL_VERTICES)
 	{