From 7866fcf78c9bd44a2e0e9979136e05ec2c56070e Mon Sep 17 00:00:00 2001
From: Andrew Meadows <andrew@highfidelity.io>
Date: Wed, 18 May 2016 23:23:11 -0700
Subject: [PATCH] trim high-point convex hulls

---
 .../physics/src/PhysicalEntitySimulation.cpp   |  7 +++++++
 libraries/physics/src/ShapeFactory.cpp         | 18 ++++++++++++++++++
 libraries/shared/src/ShapeInfo.cpp             | 12 ++++++++++++
 libraries/shared/src/ShapeInfo.h               |  1 +
 4 files changed, 38 insertions(+)

diff --git a/libraries/physics/src/PhysicalEntitySimulation.cpp b/libraries/physics/src/PhysicalEntitySimulation.cpp
index 3fbf8ffaf5..95ae45bbb2 100644
--- a/libraries/physics/src/PhysicalEntitySimulation.cpp
+++ b/libraries/physics/src/PhysicalEntitySimulation.cpp
@@ -217,6 +217,13 @@ void PhysicalEntitySimulation::getObjectsToAddToPhysics(VectorOfMotionStates& re
         } else if (entity->isReadyToComputeShape()) {
             ShapeInfo shapeInfo;
             entity->computeShapeInfo(shapeInfo);
+            int numPoints = shapeInfo.getMaxNumPoints();
+            const int MAX_HULL_POINTS = 42;
+            if (numPoints > MAX_HULL_POINTS) {
+                glm::vec3 p = entity->getPosition();
+                qDebug() << "entity" << entity->getName() << "at <" << p.x << p.y << p.z << ">"
+                    << "has convex hull with" << numPoints << "points";
+            }
             btCollisionShape* shape = ObjectMotionState::getShapeManager()->getShape(shapeInfo);
             if (shape) {
                 EntityMotionState* motionState = new EntityMotionState(shape, entity);
diff --git a/libraries/physics/src/ShapeFactory.cpp b/libraries/physics/src/ShapeFactory.cpp
index de3e9cc794..8641873540 100644
--- a/libraries/physics/src/ShapeFactory.cpp
+++ b/libraries/physics/src/ShapeFactory.cpp
@@ -10,6 +10,7 @@
 //
 
 #include <glm/gtx/norm.hpp>
+#include <BulletCollision/CollisionShapes/btShapeHull.h>
 
 #include <SharedUtil.h> // for MILLIMETERS_PER_METER
 
@@ -64,6 +65,23 @@ btConvexHullShape* ShapeFactory::createConvexHull(const QVector<glm::vec3>& poin
         correctedPoint = (points[i] - center) * relativeScale + center;
         hull->addPoint(btVector3(correctedPoint[0], correctedPoint[1], correctedPoint[2]), false);
     }
+
+    const int MAX_HULL_POINTS = 42;
+    if (points.size() > MAX_HULL_POINTS) {
+        // create hull approximation
+        btShapeHull* shapeHull = new btShapeHull(hull);
+        shapeHull->buildHull(margin);
+        btConvexHullShape* newHull = new btConvexHullShape();
+        const btVector3* newPoints = shapeHull->getVertexPointer();
+        for (int i = 0; i < shapeHull->numVertices(); ++i) {
+            newHull->addPoint(newPoints[i], false);
+        }
+        delete hull;
+        delete shapeHull;
+        hull = newHull;
+        qDebug() << "reduced hull with" << points.size() << "points down to" << hull->getNumPoints(); // TODO: remove after testing
+    }
+
     hull->recalcLocalAabb();
     return hull;
 }
diff --git a/libraries/shared/src/ShapeInfo.cpp b/libraries/shared/src/ShapeInfo.cpp
index 1d0cd56b86..0974c88e73 100644
--- a/libraries/shared/src/ShapeInfo.cpp
+++ b/libraries/shared/src/ShapeInfo.cpp
@@ -99,6 +99,18 @@ uint32_t ShapeInfo::getNumSubShapes() const {
     }
     return 1;
 }
+
+int ShapeInfo::getMaxNumPoints() const {
+    int numPoints = 0;
+    for (int i = 0; i < _points.size(); ++i) {
+        int n = _points[i].size();
+        if (n > numPoints) {
+            numPoints = n;
+        }
+    }
+    return numPoints;
+}
+
 float ShapeInfo::computeVolume() const {
     const float DEFAULT_VOLUME = 1.0f;
     float volume = DEFAULT_VOLUME;
diff --git a/libraries/shared/src/ShapeInfo.h b/libraries/shared/src/ShapeInfo.h
index 79390b6680..71fa12d5b5 100644
--- a/libraries/shared/src/ShapeInfo.h
+++ b/libraries/shared/src/ShapeInfo.h
@@ -61,6 +61,7 @@ public:
 
     void clearPoints () { _points.clear(); }
     void appendToPoints (const QVector<glm::vec3>& newPoints) { _points << newPoints; }
+    int getMaxNumPoints() const;
 
     float computeVolume() const;