diff --git a/src/experimental/_impl/_marching_squares_impl.scad b/src/experimental/_impl/_marching_squares_impl.scad
index a18775bd..703aec88 100644
--- a/src/experimental/_impl/_marching_squares_impl.scad
+++ b/src/experimental/_impl/_marching_squares_impl.scad
@@ -130,3 +130,925 @@ function _marching_squares_isolines(points, sigma) =
     ISOLINES Impl End ============================
 */
 
+/*
+    ISOBANDS Impl Begin ============================
+*/
+
+function _isobands_tri_label(pts, lower, upper) =
+    [
+        for(row = pts)
+        [
+            for(p = row) 
+            let(label = 
+                p[2] < lower ? "0" : 
+                p[2] >= lower && p[2] < upper ? "1" : "2"
+            )
+            [p[0], p[1], p[2], label]
+        ]
+    ]; 
+    
+function _isobands_corner_value(cell_pts) =
+    str(cell_pts[1][3], cell_pts[2][3], cell_pts[3][3], cell_pts[0][3]); 
+
+// single triangle
+function _case2221_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+    ]
+];
+
+function _case2212_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma)
+    ]
+];
+
+function _case2122_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]]
+    ]
+];
+    
+function _case1222_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma),
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+
+function _case0001_isobands(cell_pts, sigma) = 
+    _case2221_isobands(cell_pts, sigma);
+    
+function _case0010_isobands(cell_pts, sigma) = 
+    _case2212_isobands(cell_pts, sigma);
+    
+function _case0100_isobands(cell_pts, sigma) = 
+    _case2122_isobands(cell_pts, sigma);
+
+function _case1000_isobands(cell_pts, sigma) = 
+    _case1222_isobands(cell_pts, sigma);
+    
+ // single trapezoid
+function _case2220_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];
+
+function _case2202_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper)
+    ]
+];
+
+function _case2022_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        interpolated_pt(cell_pts[0], cell_pts[1], lower)
+    ]
+];
+    
+function _case0222_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower)
+    ]
+];
+    
+function _case0002_isobands(cell_pts, lower, upper) = 
+    _case2220_isobands(cell_pts, upper, lower);
+
+function _case0020_isobands(cell_pts, lower, upper) = 
+    _case2202_isobands(cell_pts, upper, lower);
+    
+function _case0200_isobands(cell_pts, lower, upper) = 
+    _case2022_isobands(cell_pts, upper, lower);
+
+function _case2000_isobands(cell_pts, lower, upper) = 
+    _case0222_isobands(cell_pts, upper, lower);
+    
+// single rectangle    
+function _case0011_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+    ]
+];
+    
+function _case0110_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma)
+    ]
+];
+
+function _case1100_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma),
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+
+function _case1001_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+
+function _case2211_isobands(cell_pts, sigma) = 
+    _case0011_isobands(cell_pts, sigma);
+    
+function _case2112_isobands(cell_pts, sigma) = 
+    _case0110_isobands(cell_pts, sigma);    
+
+function _case1122_isobands(cell_pts, sigma) = 
+    _case1100_isobands(cell_pts, sigma);        
+
+function _case1221_isobands(cell_pts, sigma) = 
+    _case1001_isobands(cell_pts, sigma);   
+        
+function _case2200_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];
+
+function _case2002_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper)
+    ]
+];
+        
+function _case0022_isobands(cell_pts, lower, upper) = 
+    _case2200_isobands(cell_pts, upper, lower);
+
+function _case0220_isobands(cell_pts, lower, upper) = 
+    _case2002_isobands(cell_pts, upper, lower);
+
+// single hexagon
+function _case0211_isobands(cell_pts, lower, upper) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        interpolated_pt(cell_pts[0], cell_pts[1], lower)
+    ]
+];
+    
+function _case2110_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];
+
+function _case1102_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], upper),
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+
+function _case1021_isobands(cell_pts, lower, upper) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],    
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+    
+function _case2011_isobands(cell_pts, lower, upper) = 
+    _case0211_isobands(cell_pts, upper, lower);    
+
+function _case0112_isobands(cell_pts, lower, upper) = 
+    _case2110_isobands(cell_pts, upper, lower);    
+    
+function _case1120_isobands(cell_pts, lower, upper) = 
+    _case1102_isobands(cell_pts, upper, lower);    
+    
+function _case1201_isobands(cell_pts, lower, upper) = 
+    _case1021_isobands(cell_pts, upper, lower);    
+    
+function _case2101_isobands(cell_pts, lower, upper) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],    
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];    
+
+function _case0121_isobands(cell_pts, lower, upper) = 
+    _case2101_isobands(cell_pts, upper, lower);   
+    
+function _case1012_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],  
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],  
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];        
+    
+function _case1210_isobands(cell_pts, lower, upper) = 
+    _case1012_isobands(cell_pts, upper, lower);   
+
+// single pentagon
+function _case1211_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];
+
+function _case2111_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],        
+        interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+    ]
+];
+
+function _case1112_isobands(cell_pts, sigma) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),   
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],        
+        interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+    ]
+];   
+
+function _case1121_isobands(cell_pts, sigma) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],    
+        interpolated_pt(cell_pts[0], cell_pts[3], sigma),   
+        interpolated_pt(cell_pts[2], cell_pts[3], sigma), 
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];   
+    
+function _case1011_isobands(cell_pts, sigma) = 
+    _case1211_isobands(cell_pts, sigma);  
+
+function _case0111_isobands(cell_pts, sigma) = 
+    _case2111_isobands(cell_pts, sigma);   
+
+function _case1110_isobands(cell_pts, sigma) = 
+    _case1112_isobands(cell_pts, sigma);   
+
+function _case1101_isobands(cell_pts, sigma) = 
+    _case1121_isobands(cell_pts, sigma);       
+
+function _case1200_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+    ]
+];     
+
+function _case0120_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        interpolated_pt(cell_pts[1], cell_pts[2], lower)
+    ]
+];     
+    
+function _case0012_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];   
+
+function _case2001_isobands(cell_pts, lower, upper) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];       
+    
+function _case1022_isobands(cell_pts, lower, upper) = 
+    _case1200_isobands(cell_pts, upper, lower);
+
+function _case2102_isobands(cell_pts, lower, upper) = 
+    _case0120_isobands(cell_pts, upper, lower);
+
+function _case2210_isobands(cell_pts, lower, upper) = 
+    _case0012_isobands(cell_pts, upper, lower);
+
+function _case0221_isobands(cell_pts, lower, upper) = 
+    _case2001_isobands(cell_pts, upper, lower);    
+    
+function _case1002_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower),
+        [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+];   
+
+function _case2100_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[1], lower),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower),
+        [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[0], cell_pts[1], upper)
+    ]
+]; 
+    
+function _case0210_isobands(cell_pts, lower, upper) = [
+    [
+        interpolated_pt(cell_pts[0], cell_pts[3], lower),
+        [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]], 
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], upper),
+        interpolated_pt(cell_pts[1], cell_pts[2], lower)
+    ]
+]; 
+
+function _case0021_isobands(cell_pts, lower, upper) = [
+    [
+        [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]], 
+        interpolated_pt(cell_pts[0], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], upper),
+        interpolated_pt(cell_pts[2], cell_pts[3], lower), interpolated_pt(cell_pts[0], cell_pts[1], lower)
+    ]
+]; 
+    
+function _case1220_isobands(cell_pts, lower, upper) = 
+    _case1002_isobands(cell_pts, upper, lower);
+
+function _case0122_isobands(cell_pts, lower, upper) = 
+    _case2100_isobands(cell_pts, upper, lower);
+
+function _case2012_isobands(cell_pts, lower, upper) = 
+    _case0210_isobands(cell_pts, upper, lower);
+
+function _case2201_isobands(cell_pts, lower, upper) = 
+    _case0021_isobands(cell_pts, upper, lower);        
+    
+// Saddles
+function _case2020_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper), interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper), interpolated_pt(cell_pts[2], cell_pts[3], lower)
+        ]
+    ] :
+    mdpz >= lower && mdpz < upper ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper), interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ],
+        [
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower), interpolated_pt(cell_pts[1], cell_pts[2], lower)
+        ]        
+    ];
+    
+function _case0202_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower), interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ],
+        [
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper), interpolated_pt(cell_pts[1], cell_pts[2], upper)
+        ]        
+    ] :
+    mdpz >= lower && mdpz < upper ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower), interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower), interpolated_pt(cell_pts[2], cell_pts[3], upper)
+        ]
+    ];
+
+function _case0101_isobands(cell_pts, sigma) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < sigma ? [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma)
+        ]        
+    ] : [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ]
+    ];
+
+function _case1010_isobands(cell_pts, sigma) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < sigma ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma),
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma)
+        ]        
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ]
+    ];    
+
+function _case2121_isobands(cell_pts, sigma) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < sigma ? [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ]
+    ] : [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma)
+        ]        
+    ];        
+
+function _case1212_isobands(cell_pts, sigma) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < sigma ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma),
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], sigma),
+            interpolated_pt(cell_pts[1], cell_pts[2], sigma),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], sigma),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], sigma)
+        ]        
+    ];            
+
+function _case2120_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < upper ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ]     
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper), interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], upper)
+        ]
+    ];
+    
+function _case0102_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower), interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], lower)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            [cell_pts[2][0], cell_pts[2][1], cell_pts[2][2]],
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ]     
+    ];    
+
+function _case2021_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < upper ? [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ]     
+    ] : [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper)
+        ]
+    ];
+    
+function _case0201_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ],
+        [
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower)
+        ]
+    ] : [
+        [
+            [cell_pts[0][0], cell_pts[0][1], cell_pts[0][2]],
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ]     
+    ];    
+ 
+function _case1202_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < upper ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ]     
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper)
+        ]
+    ];
+
+function _case1020_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]]
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            [cell_pts[1][0], cell_pts[1][1], cell_pts[1][2]],
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ]     
+    ];    
+    
+function _case0212_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < upper ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ]     
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], upper),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], upper)
+        ]
+    ];    
+    
+function _case2010_isobands(cell_pts, lower, upper) = 
+    let(mdpz = (cell_pts[0][2] + cell_pts[1][2] + cell_pts[2][2] + cell_pts[3][2]) / 4)
+    mdpz < lower ? [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[1], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper)
+        ],
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], lower)
+        ]
+    ] : [
+        [
+            interpolated_pt(cell_pts[0], cell_pts[3], lower),
+            [cell_pts[3][0], cell_pts[3][1], cell_pts[3][2]],
+            interpolated_pt(cell_pts[2], cell_pts[3], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], lower),
+            interpolated_pt(cell_pts[1], cell_pts[2], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], upper),
+            interpolated_pt(cell_pts[0], cell_pts[1], lower)
+        ]     
+    ];        
+ 
+function _isobands_of(cell_pts, lower, upper) =    
+    let(cv = _isobands_corner_value(cell_pts))
+    // no contour
+    cv == "0000" ? [] : 
+    // single square
+    cv == "1111" ? [[for(i = 3; i >= 0; i = i - 1) [cell_pts[i][0], cell_pts[i][1]]]] :
+    // single triangle
+    cv == "2221" ? _case2221_isobands(cell_pts, upper) :
+    cv == "2212" ? _case2212_isobands(cell_pts, upper) :
+    cv == "2122" ? _case2122_isobands(cell_pts, upper) :
+    cv == "1222" ? _case1222_isobands(cell_pts, upper) :
+    cv == "0001" ? _case0001_isobands(cell_pts, lower) :
+    cv == "0010" ? _case0010_isobands(cell_pts, lower) :
+    cv == "0100" ? _case0100_isobands(cell_pts, lower) :
+    cv == "1000" ? _case1000_isobands(cell_pts, lower) :
+    // single trapezoid
+    cv == "2220" ? _case2220_isobands(cell_pts, lower, upper) :
+    cv == "2202" ? _case2202_isobands(cell_pts, lower, upper) :
+    cv == "2022" ? _case2022_isobands(cell_pts, lower, upper) :
+    cv == "0222" ? _case0222_isobands(cell_pts, lower, upper) :   
+    cv == "0002" ? _case0002_isobands(cell_pts, lower, upper) :       
+    cv == "0020" ? _case0020_isobands(cell_pts, lower, upper) :
+    cv == "0200" ? _case0200_isobands(cell_pts, lower, upper) :    
+    cv == "2000" ? _case2000_isobands(cell_pts, lower, upper) :     
+    // single rectangle  
+    cv == "0011" ? _case0011_isobands(cell_pts, lower) :
+    cv == "0110" ? _case0110_isobands(cell_pts, lower) :
+    cv == "1100" ? _case1100_isobands(cell_pts, lower) : 
+    cv == "1001" ? _case1001_isobands(cell_pts, lower) :
+    cv == "2211" ? _case2211_isobands(cell_pts, upper) :
+    cv == "2112" ? _case2112_isobands(cell_pts, upper) :  
+    cv == "1122" ? _case1122_isobands(cell_pts, upper) :
+    cv == "1221" ? _case1221_isobands(cell_pts, upper) :
+    cv == "2200" ? _case2200_isobands(cell_pts, lower, upper) :
+    cv == "2002" ? _case2002_isobands(cell_pts, lower, upper) :    
+    cv == "0022" ? _case0022_isobands(cell_pts, lower, upper) :     
+    cv == "0220" ? _case0220_isobands(cell_pts, lower, upper) :     
+    // single hexagon
+    cv == "0211" ? _case0211_isobands(cell_pts, lower, upper) :   
+    cv == "2110" ? _case2110_isobands(cell_pts, lower, upper) :       
+    cv == "1102" ? _case1102_isobands(cell_pts, lower, upper) :      
+    cv == "1021" ? _case1021_isobands(cell_pts, lower, upper) :     
+    cv == "2011" ? _case2011_isobands(cell_pts, lower, upper) :     
+    cv == "0112" ? _case0112_isobands(cell_pts, lower, upper) :     
+    cv == "1120" ? _case1120_isobands(cell_pts, lower, upper) :        
+    cv == "1201" ? _case1201_isobands(cell_pts, lower, upper) :       
+    cv == "2101" ? _case2101_isobands(cell_pts, lower, upper) :        
+    cv == "0121" ? _case0121_isobands(cell_pts, lower, upper) :      
+    cv == "1012" ? _case1012_isobands(cell_pts, lower, upper) :       
+    cv == "1210" ? _case1210_isobands(cell_pts, lower, upper) :     
+    // single pentagon    
+    cv == "1211" ? _case1211_isobands(cell_pts, upper) :
+    cv == "2111" ? _case2111_isobands(cell_pts, upper) :
+    cv == "1112" ? _case1112_isobands(cell_pts, upper) :   
+    cv == "1121" ? _case1121_isobands(cell_pts, upper) :
+    cv == "1011" ? _case1011_isobands(cell_pts, lower) :
+    cv == "0111" ? _case0111_isobands(cell_pts, lower) :
+    cv == "1110" ? _case1110_isobands(cell_pts, lower) :   
+    cv == "1101" ? _case1101_isobands(cell_pts, lower) :  
+    cv == "1200" ? _case1200_isobands(cell_pts, lower, upper) :      
+    cv == "0120" ? _case0120_isobands(cell_pts, lower, upper) :   
+    cv == "0012" ? _case0012_isobands(cell_pts, lower, upper) :      
+    cv == "2001" ? _case2001_isobands(cell_pts, lower, upper) :    
+    cv == "1022" ? _case1022_isobands(cell_pts, lower, upper) :      
+    cv == "2102" ? _case2102_isobands(cell_pts, lower, upper) :   
+    cv == "2210" ? _case2210_isobands(cell_pts, lower, upper) :      
+    cv == "0221" ? _case0221_isobands(cell_pts, lower, upper) :
+    cv == "1002" ? _case1002_isobands(cell_pts, lower, upper) :      
+    cv == "2100" ? _case2100_isobands(cell_pts, lower, upper) :   
+    cv == "0210" ? _case0210_isobands(cell_pts, lower, upper) :    
+    cv == "0021" ? _case0021_isobands(cell_pts, lower, upper) :        
+    cv == "1220" ? _case1220_isobands(cell_pts, lower, upper) :      
+    cv == "0122" ? _case0122_isobands(cell_pts, lower, upper) :   
+    cv == "2012" ? _case2012_isobands(cell_pts, lower, upper) :    
+    cv == "2201" ? _case2201_isobands(cell_pts, lower, upper) : 
+    // Saddles
+    cv == "2020" ? _case2020_isobands(cell_pts, lower, upper) :
+    cv == "0202" ? _case0202_isobands(cell_pts, lower, upper) :
+    cv == "0101" ? _case0101_isobands(cell_pts, lower) :
+    cv == "1010" ? _case1010_isobands(cell_pts, lower) :
+    cv == "2121" ? _case2121_isobands(cell_pts, upper) :    
+    cv == "1212" ? _case1212_isobands(cell_pts, upper) : 
+    cv == "2120" ? _case2120_isobands(cell_pts, lower, upper) :    
+    cv == "0102" ? _case0102_isobands(cell_pts, lower, upper) :   
+    cv == "2021" ? _case2021_isobands(cell_pts, lower, upper) : 
+    cv == "0201" ? _case0201_isobands(cell_pts, lower, upper) : 
+    cv == "1202" ? _case1202_isobands(cell_pts, lower, upper) :      
+    cv == "1020" ? _case1020_isobands(cell_pts, lower, upper) :  
+    cv == "0212" ? _case0212_isobands(cell_pts, lower, upper) :  
+    cv == "2010" ? _case2010_isobands(cell_pts, lower, upper) :  
+    // no contour
+    []; // 2222
+    
+function _marching_squares_isobands(points, lower, upper) = 
+    let(labeled_pts = _isobands_tri_label(points, lower, upper))
+    [
+        for(y = [0:len(labeled_pts) - 2])
+            [
+                 for(x = [0:len(labeled_pts[0]) - 2])
+                 let(
+                    p0 = labeled_pts[y][x],
+                    p1 = labeled_pts[y + 1][x],
+                    p2 = labeled_pts[y + 1][x + 1],
+                    p3 = labeled_pts[y][x + 1],
+                    cell_pts = [p0, p1, p2, p3],
+                    isobands_lt = _isobands_of(cell_pts, lower, upper)
+                 )
+                 if(isobands_lt != [])
+                 each isobands_lt
+           ]
+    ];
+    
+/*
+    ISOBANDS Impl End ============================
+*/
\ No newline at end of file
diff --git a/src/experimental/marching_squares.scad b/src/experimental/marching_squares.scad
index 2f523d54..36347fb4 100644
--- a/src/experimental/marching_squares.scad
+++ b/src/experimental/marching_squares.scad
@@ -1,3 +1,6 @@
 use <experimental/_impl/_marching_squares_impl.scad>;
 
-function marching_squares(points, sigma) = _marching_squares_isolines(points, sigma);
\ No newline at end of file
+function marching_squares(points, threshold) = 
+    is_undef(threshold[1]) ? 
+        _marching_squares_isolines(points, threshold) :
+        _marching_squares_isobands(points, threshold[0], threshold[1]);
\ No newline at end of file