diff --git a/models/piston_normal_1.obj b/models/piston_normal_1.obj
new file mode 100644
index 0000000..dd801b1
--- /dev/null
+++ b/models/piston_normal_1.obj
@@ -0,0 +1,143 @@
+# Blender v2.82 (sub 7) OBJ File: ''
+# www.blender.org
+mtllib piston_normal_1.mtl
+o cube
+v 0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 -0.312500
+v 0.500000 -0.500000 -0.312500
+v 0.500000 0.500000 0.500000
+v 0.500000 0.500000 -0.312500
+v -0.500000 0.500000 0.500000
+v -0.500000 0.500000 -0.312500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.666667
+vt 0.333333 0.666667
+vt 0.333333 0.666667
+vt 0.666667 1.000000
+vt 0.333333 1.000000
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 -0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 -0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 -0.0000 1.0000
+usemtl m_7
+s 1
+f 1/1/1 2/2/1 3/3/1 4/4/1
+f 5/5/2 1/6/2 4/7/2 6/8/2
+f 7/9/3 5/10/3 6/11/3 8/12/3
+f 2/13/4 7/14/4 8/15/4 3/16/4
+f 8/17/5 6/18/5 4/19/5 3/20/5
+f 2/21/6 1/1/6 5/22/6 7/23/6
+o cube.000
+v 0.500000 -0.500000 -1.312500
+v -0.500000 -0.500000 -1.312500
+v -0.500000 -0.500000 -1.500000
+v 0.500000 -0.500000 -1.500000
+v 0.500000 0.500000 -1.312500
+v 0.500000 0.500000 -1.500000
+v -0.500000 0.500000 -1.312500
+v -0.500000 0.500000 -1.500000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.333333 0.000000
+vt 0.666667 0.000000
+vt 0.666667 0.333333
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 1.000000 0.333333
+vt 1.000000 0.666667
+vt 0.666667 0.666667
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_7
+s 1
+f 9/24/7 10/25/7 11/26/7 12/27/7
+f 13/28/8 9/29/8 12/30/8 14/31/8
+f 15/32/9 13/33/9 14/34/9 16/35/9
+f 10/36/10 15/37/10 16/38/10 11/39/10
+f 16/40/11 14/41/11 12/42/11 11/43/11
+f 10/44/12 9/45/12 13/46/12 15/47/12
+o cube.001
+v 0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 -1.375000
+v 0.125000 -0.125000 -1.375000
+v 0.125000 0.125000 0.375000
+v 0.125000 0.125000 -1.375000
+v -0.125000 0.125000 0.375000
+v -0.125000 0.125000 -1.375000
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.458333 0.130208
+vt 0.541667 0.130208
+vt 0.541667 0.213542
+vt 0.458333 0.213542
+vt 0.791667 0.463542
+vt 0.875000 0.463542
+vt 0.875000 0.546875
+vt 0.791667 0.546875
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_7
+s 1
+f 17/48/13 18/49/13 19/50/13 20/51/13
+f 21/52/14 17/53/14 20/54/14 22/55/14
+f 23/56/15 21/57/15 22/58/15 24/59/15
+f 18/60/16 23/61/16 24/62/16 19/63/16
+f 24/64/17 22/65/17 20/66/17 19/67/17
+f 18/68/18 17/69/18 21/70/18 23/71/18
diff --git a/models/piston_normal_2.obj b/models/piston_normal_2.obj
new file mode 100644
index 0000000..657411d
--- /dev/null
+++ b/models/piston_normal_2.obj
@@ -0,0 +1,143 @@
+# Blender v2.82 (sub 7) OBJ File: ''
+# www.blender.org
+mtllib piston_normal_2.mtl
+o cube.011
+v 0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 -0.312500
+v 0.500000 -0.500000 -0.312500
+v 0.500000 0.500000 0.500000
+v 0.500000 0.500000 -0.312500
+v -0.500000 0.500000 0.500000
+v -0.500000 0.500000 -0.312500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.666667
+vt 0.333333 0.666667
+vt 0.333333 0.666667
+vt 0.666667 1.000000
+vt 0.333333 1.000000
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 -0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 -0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 -0.0000 1.0000
+usemtl m_0.001
+s 1
+f 1/1/1 2/2/1 3/3/1 4/4/1
+f 5/5/2 1/6/2 4/7/2 6/8/2
+f 7/9/3 5/10/3 6/11/3 8/12/3
+f 2/13/4 7/14/4 8/15/4 3/16/4
+f 8/17/5 6/18/5 4/19/5 3/20/5
+f 2/21/6 1/1/6 5/22/6 7/23/6
+o cube.012
+v 0.500000 -0.500000 -2.312500
+v -0.500000 -0.500000 -2.312500
+v -0.500000 -0.500000 -2.500000
+v 0.500000 -0.500000 -2.500000
+v 0.500000 0.500000 -2.312500
+v 0.500000 0.500000 -2.500000
+v -0.500000 0.500000 -2.312500
+v -0.500000 0.500000 -2.500000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.333333 0.000000
+vt 0.666667 0.000000
+vt 0.666667 0.333333
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 1.000000 0.333333
+vt 1.000000 0.666667
+vt 0.666667 0.666667
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_0.001
+s 1
+f 9/24/7 10/25/7 11/26/7 12/27/7
+f 13/28/8 9/29/8 12/30/8 14/31/8
+f 15/32/9 13/33/9 14/34/9 16/35/9
+f 10/36/10 15/37/10 16/38/10 11/39/10
+f 16/40/11 14/41/11 12/42/11 11/43/11
+f 10/44/12 9/45/12 13/46/12 15/47/12
+o cube.013
+v 0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 -2.375000
+v 0.125000 -0.125000 -2.375000
+v 0.125000 0.125000 0.375000
+v 0.125000 0.125000 -2.375000
+v -0.125000 0.125000 0.375000
+v -0.125000 0.125000 -2.375000
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.562500 0.229167
+vt 0.458333 0.229167
+vt 0.458333 0.125000
+vt 0.562500 0.125000
+vt 0.875000 0.458333
+vt 0.791667 0.458333
+vt 0.791667 0.541667
+vt 0.875000 0.541667
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_0.001
+s 1
+f 17/48/13 18/49/13 19/50/13 20/51/13
+f 21/52/14 17/53/14 20/54/14 22/55/14
+f 23/56/15 21/57/15 22/58/15 24/59/15
+f 18/60/16 23/61/16 24/62/16 19/63/16
+f 24/64/17 22/65/17 20/66/17 19/67/17
+f 18/68/18 17/69/18 21/70/18 23/71/18
diff --git a/models/piston_sticky_1.obj b/models/piston_sticky_1.obj
new file mode 100644
index 0000000..21b8c1d
--- /dev/null
+++ b/models/piston_sticky_1.obj
@@ -0,0 +1,143 @@
+# Blender v2.82 (sub 7) OBJ File: ''
+# www.blender.org
+mtllib piston_sticky_1.mtl
+o cube.002
+v 0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 -0.312500
+v 0.500000 -0.500000 -0.312500
+v 0.500000 0.500000 0.500000
+v 0.500000 0.500000 -0.312500
+v -0.500000 0.500000 0.500000
+v -0.500000 0.500000 -0.312500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.666667
+vt 0.333333 0.666667
+vt 0.333333 0.666667
+vt 0.666667 1.000000
+vt 0.333333 1.000000
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 -0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 -0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 -0.0000 1.0000
+usemtl m_7.001
+s 1
+f 1/1/1 2/2/1 3/3/1 4/4/1
+f 5/5/2 1/6/2 4/7/2 6/8/2
+f 7/9/3 5/10/3 6/11/3 8/12/3
+f 2/13/4 7/14/4 8/15/4 3/16/4
+f 8/17/5 6/18/5 4/19/5 3/20/5
+f 2/21/6 1/1/6 5/22/6 7/23/6
+o cube.003
+v 0.500000 -0.500000 -1.312500
+v -0.500000 -0.500000 -1.312500
+v -0.500000 -0.500000 -1.500000
+v 0.500000 -0.500000 -1.500000
+v 0.500000 0.500000 -1.312500
+v 0.500000 0.500000 -1.500000
+v -0.500000 0.500000 -1.312500
+v -0.500000 0.500000 -1.500000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.000000
+vt 1.000000 0.000000
+vt 1.000000 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.333333
+vt 1.000000 0.333333
+vt 1.000000 0.666667
+vt 0.666667 0.666667
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_7.001
+s 1
+f 9/24/7 10/25/7 11/26/7 12/27/7
+f 13/28/8 9/29/8 12/30/8 14/31/8
+f 15/32/9 13/33/9 14/34/9 16/35/9
+f 10/36/10 15/37/10 16/38/10 11/39/10
+f 16/40/11 14/41/11 12/42/11 11/43/11
+f 10/44/12 9/45/12 13/46/12 15/47/12
+o cube.004
+v 0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 -1.375000
+v 0.125000 -0.125000 -1.375000
+v 0.125000 0.125000 0.375000
+v 0.125000 0.125000 -1.375000
+v -0.125000 0.125000 0.375000
+v -0.125000 0.125000 -1.375000
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.354167
+vt 0.208333 0.354167
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.458333 0.130208
+vt 0.541667 0.130208
+vt 0.541667 0.213542
+vt 0.458333 0.213542
+vt 0.791667 0.463542
+vt 0.875000 0.463542
+vt 0.875000 0.546875
+vt 0.791667 0.546875
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_7.001
+s 1
+f 17/48/13 18/49/13 19/50/13 20/51/13
+f 21/52/14 17/53/14 20/54/14 22/55/14
+f 23/56/15 21/57/15 22/58/15 24/59/15
+f 18/60/16 23/61/16 24/62/16 19/63/16
+f 24/64/17 22/65/17 20/66/17 19/67/17
+f 18/68/18 17/69/18 21/70/18 23/71/18
diff --git a/models/piston_sticky_2.obj b/models/piston_sticky_2.obj
new file mode 100644
index 0000000..fe233be
--- /dev/null
+++ b/models/piston_sticky_2.obj
@@ -0,0 +1,143 @@
+# Blender v2.82 (sub 7) OBJ File: ''
+# www.blender.org
+mtllib piston_sticky_2.mtl
+o cube.008
+v 0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 -0.312500
+v 0.500000 -0.500000 -0.312500
+v 0.500000 0.500000 0.500000
+v 0.500000 0.500000 -0.312500
+v -0.500000 0.500000 0.500000
+v -0.500000 0.500000 -0.312500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.666667 0.666667
+vt 1.000000 0.666667
+vt 1.000000 0.937500
+vt 0.666667 0.937500
+vt 0.333333 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.666667
+vt 0.333333 0.666667
+vt 0.333333 0.666667
+vt 0.666667 1.000000
+vt 0.333333 1.000000
+vn 0.0000 -1.0000 0.0000
+vn 1.0000 -0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 -0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 -0.0000 1.0000
+usemtl m_0
+s 1
+f 1/1/1 2/2/1 3/3/1 4/4/1
+f 5/5/2 1/6/2 4/7/2 6/8/2
+f 7/9/3 5/10/3 6/11/3 8/12/3
+f 2/13/4 7/14/4 8/15/4 3/16/4
+f 8/17/5 6/18/5 4/19/5 3/20/5
+f 2/21/6 1/1/6 5/22/6 7/23/6
+o cube.009
+v 0.500000 -0.500000 -2.312500
+v -0.500000 -0.500000 -2.312500
+v -0.500000 -0.500000 -2.500000
+v 0.500000 -0.500000 -2.500000
+v 0.500000 0.500000 -2.312500
+v 0.500000 0.500000 -2.500000
+v -0.500000 0.500000 -2.312500
+v -0.500000 0.500000 -2.500000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.937500
+vt 1.000000 0.937500
+vt 1.000000 1.000000
+vt 0.666667 1.000000
+vt 0.666667 0.000000
+vt 1.000000 0.000000
+vt 1.000000 0.333333
+vt 0.666667 0.333333
+vt 0.666667 0.333333
+vt 1.000000 0.333333
+vt 1.000000 0.666667
+vt 0.666667 0.666667
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_0
+s 1
+f 9/24/7 10/25/7 11/26/7 12/27/7
+f 13/28/8 9/29/8 12/30/8 14/31/8
+f 15/32/9 13/33/9 14/34/9 16/35/9
+f 10/36/10 15/37/10 16/38/10 11/39/10
+f 16/40/11 14/41/11 12/42/11 11/43/11
+f 10/44/12 9/45/12 13/46/12 15/47/12
+o cube.010
+v 0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 0.375000
+v -0.125000 -0.125000 -2.375000
+v 0.125000 -0.125000 -2.375000
+v 0.125000 0.125000 0.375000
+v 0.125000 0.125000 -2.375000
+v -0.125000 0.125000 0.375000
+v -0.125000 0.125000 -2.375000
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.125000 0.020833
+vt 0.208333 0.020833
+vt 0.208333 0.979167
+vt 0.125000 0.979167
+vt 0.562500 0.229167
+vt 0.458333 0.229167
+vt 0.458333 0.125000
+vt 0.562500 0.125000
+vt 0.875000 0.458333
+vt 0.791667 0.458333
+vt 0.791667 0.541667
+vt 0.875000 0.541667
+vn 0.0000 -1.0000 -0.0000
+vn 1.0000 0.0000 0.0000
+vn 0.0000 1.0000 0.0000
+vn -1.0000 0.0000 0.0000
+vn 0.0000 0.0000 -1.0000
+vn 0.0000 0.0000 1.0000
+usemtl m_0
+s 1
+f 17/48/13 18/49/13 19/50/13 20/51/13
+f 21/52/14 17/53/14 20/54/14 22/55/14
+f 23/56/15 21/57/15 22/58/15 24/59/15
+f 18/60/16 23/61/16 24/62/16 19/63/16
+f 24/64/17 22/65/17 20/66/17 19/67/17
+f 18/68/18 17/69/18 21/70/18 23/71/18