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VScad3 Geometric Entities
2.4.5 Surface mode.
This mode is used for creating surfaces of various types. In this mode, no mouse clicks have any effect. All surfaces are created via the surface "Geometry..." button.
"Type" : Use this list to select the type of surface to create.
"Geometry..." : This button will bring up the surface geometry dialog. The contents of this dialog depend upon the type of surface being created.
"Rectangular" : The "Rectangular Surface" dialog allows a rectangular surface mesh to be created. A rectangular surface is basically a Cartesian grid of XY points with a Z height at each point (vertex).

The "X Grid Position" field specifies the X coordinate of each "column" of points in the mesh. The values can be typed in manually (one X coordinate per line). To generate evenlyspaced coordinates automatically, type the minimum and maximum X extents of the surface on the first two lines. Then enter the desired number of points along the X dimension in the "X Interval" field and click on "Generate". Values can also be loaded from a simple ASCII ".dat" file containing one column of numbers via the X Grid Position "Load From File..." button.

The "Y Grid Position" field specifies the Y coordinate of each "row" of points in the mesh. The values can be typed in manually (one Y coordinate per line). To generate evenlyspaced coordinates automatically, type the minimum and maximum Y extents of the surface on the first two lines. Then enter the desired number of points along the Y dimension in the "Y Interval" field and click on "Generate". Values can also be loaded from a simple ASCII ".dat" file containing one column of numbers via the Y Grid Position "Load From File..." button.

The "Z Position" field specifies the Z coordinates for each XY vertex. The number of Z Positions must be equal to the number of X Grid Positions times the number of Y Grid Positions (there must be exactly one Z value for each XY vertex). To generate Z position values automatically for a flat surface, set the "Z Plane" value and click on "Generate". The "X Interval" and "Y Interval" must be set greater than 1 for the Z Position "Generate" button to function. The Z Positions can also be loaded from a simple ASCII ".dat" file containing one column of numbers. Use the Z Position "Load From File..." button to load such a file.

In the "Vertex Color(s)" field, enter the vertex colors as RGB (red, green, blue intensities  one color per line). Minimum intensity is 0 and maximum intensity is 255. If there are more vertices than colors, then the color sequence is repeated as needed. If only one color is specified, then the entire surface will be that color. The Vertex Colors "Load From File..." button allows a simple ASCII ".dat" file containing 3 columns of R,G,B (Red, Green, Blue) values to be loaded and used as the colors.
 The "Import Data" button can be used to load a VS3D relief surface (".vs3") file. When loaded, all fields in the Rectangular Surface dialog are set accordingly. Click on "Ok" to create the surface with the chosen settings.
