Mixed layer height calculations

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The complexities of mathematical calculation are not relevant when slicers simply stop with one layer height and move up the amount of the next, as they should. s3d seems to require the complex calculations, or else it will leave an air gap or complain of overlaps, while slic3r seems to have no problem with just changing to the new layer height.

Primary Relevance of Mixed Layer Heights

While a designer/printer may want to change layer heights for a variety of design reasons, including structural needs, smoothing/surface treatment, etc., perhaps the most common need is to optimize print speed (thicker layers allowing for shorter total print time), while using finer layer [heights] for parts of an object requiring finer detail or better handling of shallow slopes.

Example problem:

Object with a desired mixing of layer heights

An object printed in two parts:

  1. The layer height must be changed at or lower than 27.5mm in the printed object
  2. The bottom portion is composed of layers with a height of 0.35mm
  3. The top portion is composed of layers with a height 0.15mm

Additional practical provisions:

  1. The layer heights are not necessarily fixed requirements. For example:
    1. A maximum of .35mm might be required for the faster part of the print, but the user may accept down to .30mm.
    2. The .15mm may be desired, but the user may tolerate a range from, for example, .13-.17mm.
  2. The number of decimal places in variations in height need to be acceptable by the slicer; for instance, you may not want or be able to specify a layer height more than 3 decimal places (ex: 14.375mm)

= Complications of Calculation

... Work in progress ...