All constructed scan surfaces start out as dependent surfaces and must be created from a single input -- a patch scan. The patch scan must contain at least two rows with four points per row. PC-DMIS uses thinning tolerances to control the tightness of the surface fit.
Small tolerances: If the thinning tolerances are small, the algorithm attempts to fit the surface through all of the points in the scan.
Large tolerances: If the thinning tolerances are large, the surface is more of an approximation to the scan. The best way to see this is to construct a surface, change the thinning tolerances, and see how the shape of the surface changes.
The smaller the thinning tolerance, the longer it takes to create the surface. Be aware that the small tolerances (.01 - .05) may take a considerable amount of time (one hour) to create the surface if the input scan is large or not well behaved. Valid thinning tolerances range from 0.01 to 5.0 with a default of 0.5.
You can control the appearance of the surface with the surface grid density values. The surface displays as an N x M mesh of polylines with the default being a 5x5 mesh and the lowest value being a 2x2 mesh. To make a dependent surface independent so that it is no longer associated with the input scan, change the DEPENDENT field in the Edit window.
The shape of the surface cannot be changed.
To construct a Dependent or Independent Surface:
Open the Construct Surface dialog box (Insert | Feature | Constructed | Surface).
Select the Scan Surface option from the Method list.
Set the value for the Thinning Tol U: box.
Set the value for the Thinning Tol V: box. This applies a tolerance value to the V axis.
Set the values for the surface grid density.
Select the desired constructions options. These include:
Optimize Surface
Apply Tension Factor
Create Corners
Smooth Bad Data
Select a patch scan feature set containing at least two rows with four points per row.
Click the Create button.
More: