Density, DRT, and Wall Thickness Explained

Density

Density controls how much of the envelope volume is filled with solid material. It is expressed as a volume fraction percentage: a density of 10 means 10% of the envelope volume is solid ADMS material, and 90% is void.

A higher density produces a denser, heavier, stiffer structure with tighter cell spacing. A lower density produces a lighter, more open structure.

Density value	Character	Typical use
2 to 8%	Very open, lightweight	Minimum material, maximum void
8 to 15%	Standard lightweight	Most structural lightweighting applications
15 to 25%	Medium density	Higher load-bearing, energy absorption
25 to 32%	Dense	Maximum structural performance within the supported range

Note: Keep density between 2 and 32. Values below 2 risk generating empty results. Values above 32 increase memory use significantly and may exceed cloud computation limits.

Density gradients

You are not limited to a single constant density. By placing two or more field points at different locations with different density values, Spherene interpolates a smooth density gradient across the envelope. Material concentrates where density is high and thins out where it is low.

This is one of ADMS's core advantages over uniform lattices: a single structure can be dense near a load-bearing surface and light in the interior, all generated automatically in one computation.

DRT (Density Reference Thickness)

DRT is the reference wall thickness used to compute density. The relationship is defined by this formula:

Density = (Surface area of the ADMS x DRT) / Envelope volume x 100%

In plain terms: for a given envelope volume, a thicker DRT produces a lower cell count and simpler geometry at the same density value. A thinner DRT produces more cells and more complex geometry.

DRT also acts as the constant wall thickness when no Thickness field is assigned. So if you set DRT to 0.4 mm and do not add any thickness field points, every wall in the resulting ADMS will be 0.4 mm thick.

DRT range	Typical application	Notes
0.6 to 1.0 mm	Early design exploration	Fast compute time. Use during iteration.
0.4 mm	Standard production	Good balance of quality and compute speed. Default.
0.2 to 0.3 mm	High-resolution output	Use only for final production exports.
Below 0.2 mm	Not recommended for most work	Extreme compute cost. Only for specialist applications.

The compute cost of DRT

DRT has a non-linear impact on compute time and memory. This is the most important thing to understand when planning your workflow:

DRT change	Compute time	Memory
Halved (e.g. 0.4 to 0.2 mm)	Up to 8x longer	Up to 6x more
Quartered (e.g. 0.4 to 0.1 mm)	Up to 64x longer	Up to 36x more

The practical consequence: always work at 0.4 mm or higher during design iteration. Drop to 0.2 mm only when you are ready to export the final geometry for printing.

Wall thickness

Wall thickness is the physical thickness of the ADMS surface walls in millimetres. It determines the printability and structural performance of the final geometry.

There are two ways to set it:

Via DRT: if no Thickness field is assigned, DRT acts as the constant wall thickness throughout the structure.
Via a Thickness field: place one or more thickness field points with explicit values in mm. This overrides DRT as the wall thickness controller, while DRT continues to control density computation.

For FFF/FDM printing, a good starting point for wall thickness is your nozzle diameter. For metal AM (LPBF/SLM), typical values range from 0.2 to 0.8 mm depending on the alloy and process.

You can combine a density gradient and a thickness gradient in the same computation, giving you independent control over how much material is present and how thick each wall is at every location in the part.

Tip: When setting wall thickness via a Thickness field, the effective thickness at each point is the value you assigned. DRT still governs density computation, but does not affect physical wall thickness at that location.