Create Isosurface from Voxel

Use the Create Isosurface from Voxel option (geogxnet.dll(Geosoft.GX.VoxUtils.VoxelSurface;Run)*), to extract an isosurface from a voxel model and plot it to the 3D Viewer. The isosurface will be saved to a geosurface file.

You can access the option from:

• The Oasis montaj Geosurface > New > Create Isosurface from Voxel menu

• The Oasis montaj 3D View >  Geosurface > Isosurface > Create Isosurface from Voxel menu

• The 3D Viewer Geosurface > Isosurface > Create Isosurface menu

Create Isosurface from Voxel dialog options

Input voxel name	Select the voxel file from which the isosurface is to be extracted. Script Parameter: VOXISOSURFACE.VOXEL
Output geosurface name	Specify the name of the geosurface file. The default name is the same as the voxel file name. Script Parameter: VOXISOSURFACE.SURFACEFILE
Append to geosurface	Select the Append to geosurface option to append the newly created surface to an existing Output geosurface file. The isosurface can be appended to a geosurface as long as the voxel used to create the geosurface is the same as the input voxel. Appending the same surface value to the geosurface will overwrite the surface value and will update the colour if it was changed. If the option is disabled and the output geosurface exists, you will be prompted if you want to overwrite the output file. Script Parameter: VOXISOSURFACE.APPEND (Use 1 for append, 0 for overwrite)
Surface Properties
Value	Select the value for the isosurface. This is the 3D contour value at which the surface will be created. The value you enter must be a data value in the voxel range. Script Parameter: VOXISOSURFACE.VALUE
Colour	Click on the Colour scheme to change the colour of your isosurface. Script Parameter: VOXISOSURFACE.COLOR (Use the standard Geosoft RGB colour string format, e.g. "R128G64")
Create closed surface	Select this option to create a closed isosurface using one of the closing options below. Leaving this option unselected will create an open isosurface. Script Parameter: VOXISOSURFACE.CLOSED_FLAG (Use 0 for open, 1 for closed). If 0, the VOXISOSURFACE.CLOSED_OPTION value is ignored. Around higher values This will create the closed surface so that the value and all values higher than it are inside the surface. Script Parameter: VOXISOSURFACE.CLOSED_OPTION (0 for closed around higher values) Around lower values This will create the closed surface so that the value and all values lower than it are inside the surface. Script Parameter: VOXISOSURFACE.CLOSED_OPTION (1 for closed around lower values) Between values This will create the closed surface so that is closed between the From and To values shown below. Script Parameters: VOXISOSURFACE.CLOSED_OPTION (2 for closed between values) VOXISOSURFACE.MAX_VALUE (Use this parameter to set the "To" value, ignored for all other cases; set the "From" value using the VOXISOSURFACE.VALUE parameter)

Application Notes

A 3D surface that passes through points of equal value is called an isosurface. Isosurfaces can be thought of as 3D contours and can be used to visualize grade shells, or other volumes of interest.

Isosurfaces are saved to a Geosoft geosurface file. A geosurface file can contain more than one isosurface. Multiple isosurfaces can be appended to a single geosurface file, as long as the Input voxel used to create the isosurfaces is the same. Appending a new isosurface with the same surface value as an existing one will overwrite the existing surface (if the colour or closed options were changed, the surface will be visibly different). If Append to geosurface is not selected and the Output geosurface exists, you will be prompted if you want to overwrite the output file.

When using the "Open option", it is still possible to have a closed isosurface generated as the output surface, if the data forms a closed isosurface at the chosen value. Choosing the "Closed option", however, will force the output surface to be closed around any undefined areas (such as where the surface meets the edges of the voxel, or where the surface meets an area of null values). A closed surface can 'wrap' around values that are lower than the surface value, around values that are higher than the surface value, or between two user specified values, depending on the option selected.

The surface is calculated using an implementation of the "Marching Cubes Algorithm" originally developed by Lorensen and Cline ¹.

Visually Clip a Voxel and Create an Isosurface

• From within the 3D Viewer, select the voxel in the tree list and then select the Clipping tab.
• Clip the Data values of the voxel and then click the Define isosurface using data clipping values button:



• The Create Isosurface from Voxel dialog appears, which is automatically populated with the Input voxel name, Output geosurface name, Surface value and Colour values.

Reference