diff --git a/ode.go b/ode.go
index 8a68777..a4cd8a9 100644
--- a/ode.go
+++ b/ode.go
@@ -40,9 +40,11 @@ type nearCallbackData struct {
 	fn   NearCallback
 }
 
+var nearCallbackDataMap = NewCGOMap()
+
 //export nearCallback
 func nearCallback(data unsafe.Pointer, obj1, obj2 C.dGeomID) {
-	cbData := (*nearCallbackData)(data)
+	cbData := nearCallbackDataMap.Get(int(uintptr(data))).(*nearCallbackData)
 	cbData.fn(cbData.data, cToGeom(obj1), cToGeom(obj2))
 }
 
@@ -183,7 +185,7 @@ type VertexList Matrix
 
 // NewVertexList returns a new VertexList instance.
 func NewVertexList(size int, vals ...float64) VertexList {
-	return VertexList(NewMatrix(size, 3, 1, vals...))
+	return VertexList(NewMatrix(size, 3, 4, vals...))
 }
 
 // PlaneList represents a list of plane definitions.
diff --git a/space.go b/space.go
index ce6ee4f..a8550c7 100644
--- a/space.go
+++ b/space.go
@@ -42,6 +42,7 @@ type Space interface {
 	NewCapsule(radius, length float64) Capsule
 	NewCylinder(radius, length float64) Cylinder
 	NewRay(length float64) Ray
+	NewTriMesh(data TriMeshData) TriMesh
 	NewHeightfield(data HeightfieldData, placeable bool) Heightfield
 	NewSimpleSpace() SimpleSpace
 	NewHashSpace() HashSpace
@@ -152,7 +153,9 @@ func (s SpaceBase) Geom(index int) Geom {
 // Collide tests for collision between  contained objects.
 func (s SpaceBase) Collide(data interface{}, cb NearCallback) {
 	cbData := &nearCallbackData{fn: cb, data: data}
-	C.dSpaceCollide(s.c(), unsafe.Pointer(cbData),
+	index := nearCallbackDataMap.Set(cbData)
+	defer nearCallbackDataMap.Delete(index)
+	C.dSpaceCollide(s.c(), unsafe.Pointer(uintptr(index)),
 		(*C.dNearCallback)(C.callNearCallback))
 }
 
diff --git a/trimesh.go b/trimesh.go
index a3ece0c..404dac6 100644
--- a/trimesh.go
+++ b/trimesh.go
@@ -25,6 +25,11 @@ func (t TriMeshData) c() C.dTriMeshDataID {
 	return C.dTriMeshDataID(unsafe.Pointer(t))
 }
 
+var (
+	vertexListMap = map[int]VertexList{}
+	indexListMap  = map[int]TriVertexIndexList{}
+)
+
 // NewTriMeshData returns a new TriMeshData instance.
 func NewTriMeshData() TriMeshData {
 	return cToTriMeshData(C.dGeomTriMeshDataCreate())
@@ -32,13 +37,19 @@ func NewTriMeshData() TriMeshData {
 
 // Destroy destroys the triangle mesh data.
 func (t TriMeshData) Destroy() {
+	delete(vertexListMap, int(t))
+	delete(indexListMap, int(t))
 	C.dGeomTriMeshDataDestroy(t.c())
 }
 
 // Build builds a triangle mesh from the given data.
 func (t TriMeshData) Build(verts VertexList, tris TriVertexIndexList) {
+	delete(vertexListMap, int(t))
+	delete(indexListMap, int(t))
 	C.dGeomTriMeshDataBuildSimple(t.c(), (*C.dReal)(&verts[0][0]), C.int(len(verts)),
-		(*C.dTriIndex)(&tris[0][0]), C.int(len(tris)))
+		(*C.dTriIndex)(&tris[0][0]), C.int(len(tris)*3))
+	vertexListMap[int(t)] = verts // avoid GC mark and sweep
+	indexListMap[int(t)] = tris   // avoid GC mark and sweep
 }
 
 // Preprocess preprocesses the triangle mesh data.
diff --git a/utils.go b/utils.go
new file mode 100644
index 0000000..b18a331
--- /dev/null
+++ b/utils.go
@@ -0,0 +1,30 @@
+package ode
+
+type CGOMap struct {
+	index    int
+	pointers map[int]interface{}
+}
+
+func NewCGOMap() CGOMap {
+	var m CGOMap
+	m.pointers = make(map[int]interface{})
+	return m
+}
+
+func (m CGOMap) Get(index int) interface{} {
+	p := m.pointers[index]
+	if p == nil {
+		panic("couldn't retrieve the pointer")
+	}
+	return p
+}
+
+func (m CGOMap) Set(p interface{}) int {
+	m.index += 1
+	m.pointers[m.index] = p
+	return m.index
+}
+
+func (m CGOMap) Delete(index int) {
+	delete(m.pointers, index)
+}