Depth-Width Curve storage chambers are defined by a curve with three values:

• Depth - The depth of the chamber at that point in the curve.
• Inner Width - The internal width of the storage chamber.
• Outer Width - The width of the entire structure at that point in the curve.

Take the following example assuming an install length 10 ft

There are a few things to note:

1. The inner polygon is defined by the first non zero number and the last non zero number. If you notice at depth 3 the inner width is 0 which implies that the previous inner width is the top of the internal storage structure.
2. If you make an outer width that is less than or equal to the inner width it is assumed that the outer width equals the inner width.
3. You can only have one open internal opening; i.e the inner width can't go to 0 as the depth increases and then opens up again.
4. If you want the inner width to converge to 0 you have to put in a very small number as opposed to 0.

The total storage volume of the above chamber is just the summation of the inner trapezoidal areas multiplied by the install length:

[0.5*(6+4)*1 + 0.5(4+2)*1)*10 = 30

The total spatial volume is the sum of the outer trapezoidal areas multiplied by the install length:

[0.5*(8+6)*1 + 0.5(6+4)*1 +0.5(4+2)* 1)*10 = 160

You can also do more complex shapes, giving a bottom to the structure like: