Surface - Bicubic Mesh Surface

Navigation: Geometry > Surfaces > Surface Types > Bicubic Mesh Surface

Bicubic Mesh Surface

Page Contents

Description

Navigation

Controls

Application Notes

•Surface deformations

•Reading data from a file

•Image Import

•CodeV INT Import

•Surface isn't shown properly in 3D view

Related Topics

Description

The Bicubic Mesh surface represents Z-surface sag for X,Y positions as provided by tabular data. For this surface type, the sample points are on a rectilinear grid in X and Y. Existing tabular data can also be re-scaled using the Set/Scale Mesh Row/Col/Surface Data dialog.

When creating a bicubic mesh surface it is recommended that, where possible, the aperture of the surface be smaller than the mesh sample grid. Configuring the aperture in this way removes any edge interpolation effects which may be present at the boundary and lead to unexpected results. If the bicubic mesh surface is being used as a deformer, then the aperture does not need to be adjusted in this way.

Navigation

This feature can be accessed by selecting Bicubic Mesh Surface (Sample points define smoothly connected patches) as the surface type in the Surface tab of a surface dialog box.

Controls

Control	Inputs / Description	Defaults
Logical Parent	Name of Parent entity.	Custom Element Name
Name	Name of surface supplied by user.	Surf n
Description	Description of the surface.
Traceable	Surface can be raytraced.	Checked
Use for trimming only	Never raytrace. Surface used for trimming only.	Unchecked
Type	Surface type.	Bicubic Mesh Surface
Mesh Z(x,y)
Data Table	User input data or read from file. There are two steps for entering data in the table when not reading data from a file. Step 1: Right mouse click in the data table and select "Set/Scale Mesh Row/Col/Surf Data" from the popup menu. This will take the user to the Set/Scale Mesh dialog where the ranges and samples for the X and Y axes can be specified in the "Set X,Y Range(s)" section of the dialog. Step 2: With the X and Y axes sampling and ranges set, the Z sag data can now be entered for the corresponding x,y position.

OK	Accept settings and close dialog box.
Cancel	Discard settings and close dialog box.
Apply	Accept settings and keep dialog box open.
Help	Access this Help page.

Application Notes

Surface deformations

The Bicubic Mesh Surface is a sagable surface. A "sagable" surface is defined as single-valued in z.

Reading data from file

A properly formatted text file can be used for reading data from a file, which should have a *.dat extension. This option can be accessed by right mouse clicking in the data spread sheet area and selecting "Read from file" from the list menu. The file contains two header lines, the first line reading "type mesh" and the second line reading "format". Following the header lines are rows of data points with the first row and first column specifying the X and Y positions. The remaining data points represent the Z-values.

Image Import

Bicubic mesh data can be loaded directly from an image file by taking the following actions:

• Right mouse click in the bicubic mesh spreadsheet and select "Read From Image File"

The supported image file formats are:

BMP	JPG	TIF
DIB	PCX	TGA

When the image file option has been selected, the following dialog controls specify interpretation of the image.

Control	Inputs / Description	Defaults
Image Filename	Image file to be loaded into the bicubic mesh
Physical Limits of X Min / Max	Specifies the minimum and maximum spatial extents in the X direction that the image should map to.	-0.5 / 0.5
Physical Limits of Y Min / Max	Specifies the minimum and maximum spatial extents in the Y direction that the image should map to.	-0.5 / 0.5
Physical Height Limits Min / Max	Scales the bitmap pixel values to the designated min / max range.	0 / 1
Height Averaging	Applies nearest neighbor averaging with adjacent cells with the indicated half-width.	0

OK	Accept settings and close dialog box.
Cancel	Discard settings and close dialog box.
Apply	Accept settings and keep dialog box open.
Help	Access this Help page.

Importing from bitmaps or CodeV

Bicubic mesh data can be imported from bitmaps or from CodeV INT file format. These options can be accessed by right mouse clicking in the data spreadsheet area and selecting either "Read from image file" or "Read from INT file". Note: Bitmaps imported as Bicubic Mesh surfaces must have pixel counts that are a multiple of four (4) in both dimensions. Otherwise, the surface will be distorted.

Of the four INT file formats, regular Zernike, Fringe Zernike, GRID data or User-defined, only the GRID data format can be read into FRED.

Surface isn't shown properly in the 3D view

It may be the case that after entering the surface bicubic mesh data, the surface is not properly drawn in the 3D view. The most common cause of this problem is that the Trimming Volume Outer Boundary specification on the surface dialog Aperture tab does not have the proper Z-depth.