Overview 5


Flattener Mesh

The flattener tab primarily controls the fidelity of the mesh generated by SOLIDWORKS as input to ExactFlat. The first three parameters, Minimum Facet Width, Maximum Facet Width, and Curve Chord Tolerance, all control the shape and distribution of the triangles generated by SOLIDWORKS. These values can be manually set.

The maximum vertex count is a warning threshold. When SOLIDWORKS generates a mesh with a vertex count greater than this value, a warning is displayed indicating a large mesh has been created for use with ExactFlat, and the user is asked whether they wish to use the mesh or not. If the mesh is used, then ExactFlat will flatten the mesh. If the mesh is not used, then the piece will not be flattened.

When using the Target Vertex Count option, the above parameters will be scaled up or down to try and reach a mesh with a vertex count close to the target.

When using the Use Automatic Tolerance options, the above parameters are ignored, and instead, ExactFlat will automatically compute recommended parameters based on the size and shape of the mesh being flattened. The associated parameter is a percentage value indicating the quality of the mesh. In most cases, a quality of 50% is more than adequate.  A value of 100% indicates maximum recommended quality, and a value of 1% indicates minimum quality (which is usually useless).
When Automatic Pattern Rebuild is enabled, the ExactFlat pattern pieces will be rebuild to reflect the new results of the flatten upon closing the flattener dialogue.  If the option is disabled, then the patterns remain unchanged until the Update button is pressed.

Initial Flattening

ExactFlat is a two stage flattener. The first stage is a very quick initial pre-flattener designed to simply get a flat un-optimized pattern mesh. Due to various factors, the pre-flattener will often introduce flipped triangles to the pattern mesh (these represent folds in the fabric when cut out). Depending on the nature of the parts being designed with ExactFlat, you may wish to change the order of the pre- flatteners that are used to produce your initial flat pattern in order to produce a result closer to the final shape, and to reduce the number and likelihood of encountering flipped triangles.

The Fracture flattener is very well suited for developable and near-developable surfaces. When used on a developable surface, the fracture flattener will produce a perfect flat pattern that does not need optimization.The Stretch flattener is very well suited for objects with a low vertex count and double curvature. The Pelt flattener is similar to the Stretch flattener except it works for both low and medium vertex counts.


Preprocess will pre-compute data used regularly during the optimization process at the expense of delaying the start of the optimization process. The end result typically reduces the amount of time required to optimize a pattern piece. This option tends to have a negative effect in terms of time for very small pattern pieces.

Allow Newton Steps allows ExactFlat to apply steepest descent calculations during the optimization process under certain conditions. This option does increase the amount of time required to optimize a pattern piece. The option does not guarantee a better pattern, but does not degrade the quality of the pattern in any way.

No Seam Stretch will prevent the expansion or contraction of the perimeter of a pattern piece within the given tolerance factor. Caution should be used when specifying small values.  If the value is too small, a jagged saw tooth pattern may be produced in an attempt for ExactFlat to maintain the perimeter length.