The basis for the graphic resolution of parts and faces is the facet model. The standard Creo Elements/Direct Modeling faceting is normally sufficient to give an accurate resolution. However, a finer facet model may be necessary in certain situations, for example, when saving parts to an STL (stereolithography) file. (The facet model of a part or face can be seen by switching on Wire in the Show menu.)
The refinement factors that can be controlled are:
• The maximum deviation of distance between the facet model curve approximation and the actual curve.
• The maximum angle between individual segments of the facet model curve approximation.
In both cases, the smaller the value, the more accurate the facet model. The figure below shows how the distance and angle are measured.
Key to Figure:
1. Facet model curve approximation
2. Exact curve representation
3. Maximum deviation of distance
4. Maximum angle error
To modify the facet model of a part,
1. Click Structure and then, in the Part & Assembly group, click More.
2. Click Part in the Properties section.
3. Select a part in the viewport or the Structure Browser. The Part Properties dialog box opens.
4. Click Facets.
5. Specify new accuracy values in one of the following ways:
◦ Click a refinement factor (applied to the current values) from the Refine by cascade list. For example, 3 results in three times as many facets in the part; whereas a value of 0.5 results in half as many facets. The Distance and Angle fields are updated to show the calculated tolerance values.
◦ Enter specific values in the Distance and Angle data entry fields.
6. Click Close.
Note that the new values are taken to be the maximum allowable error when refining the part. The actual accuracy after the refinement may in fact be better for some or all faces.
You also have two options to specify predefined settings:
• Copy - You can copy the facet accuracy of another part. After selecting the part to refine and opening its Facets menu in Part Properties, click Copy from and then specify the part whose values you want to apply. The fields in the menu are updated to show the selected part's values.
• Default - The default Creo Elements/Direct Modeling facetting can be recalled and applied to the selected parts. After selecting the part to refine and opening its Facets menu in Part Properties, click Set to Default. The fields in the menu are cleared to show that the default values have been adopted.
Creo Elements/Direct Modeling uses the given values or refinement factor to change the number of facets on curved surfaces in the part. A high number of facets results in improved color shading, while low numbers result in improved performance. There are limits on the number of facets Creo Elements/Direct Modeling can use. For example, a complete cylindrical face can have no fewer than 8 facets.
Part in the Properties section.