Refinement is a command increasing the details of a polygonal mesh by splitting its triangles. It can be performed on the entire mesh or a selected region of the mesh.
Refinement preserves the selection: each selected triangle will be removed from the mesh and replaced with two triangles. The two new triangles lie in the same plane as the original triangle. Additional triangles besides those selected may be refined and these will not be placed in the selection after refinement.
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Click Refine
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The Refine dialog box is displayed. 
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Select the polygonal mesh.
You can use the Wireframe mode from the View toolbar to display the number of triangles. -
Click Apply to preview the refinement.
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Click OK to exit the command.
Before refinement After refinement
You can click Apply in the dialog box as many times as desired to perform a more precise refinement.
You can perform several selections of triangles while in the command.
