Manage the mesh settings for the current model.
Whenever you shade or render a NURBS surface, Rhino has to convert the surface into a polygon mesh to display the shaded surface on the screen. These detailed render mesh options control the way in which the surfaces are converted to polygon meshes.
On the default screen one is given the choice of:
Jagged & faster
Smooth & slower
The Detailed Controls button shows more settings for mesh fine-tuning. The following is a description of how these detailed settings work.
How meshes are created - The mesh is created in three steps based on the detailed criteria: initial quads (estimated to roughly meet the criteria), refinement (subdivision to meet the criteria), and adjustment for trim boundaries. Surfaces are meshed in a two step process. First a regular quad mesh is created and then that mesh is refined by splitting some quads into four smaller quads. The Maximum aspect ratio, Maximum edge length, and Minimum initial grid quads settings control the generation of the initial mesh. The Density (Rhino 4 only), Maximum angle, Maximum edge length, Minimum edge length, and Maximum distance, edge to surface settings determine which initial quads get split up into smaller quadrangles.
Sets the maximum allowed angle between input surface normals at neighboring mesh vertices. If the angle between surface normals is greater than this setting, the mesh is further refined (more vertices are inserted) and the mesh is made denser. Two vertices are neighbors if they are at the opposite ends of a single facet edge.
The Maximum angle setting influences the meshing of same shape objects in the same way regardless of their size. It tends to make meshes denser in areas of high curvature and less dense in flatter areas.
Experiment: Make a model with a sphere, torus, and cylinder. Then scale these objects to make a small, medium, and large-sized version. Now vary Maximum angle and notice the results.
Surfaces are initially tessellated with a regular quadrangle mesh and then that mesh is refined. The initial quad mesh is constructed so that, on average, the maximum aspect ratio of the quads is less than or equal to Maximum aspect ratio.
Smaller values result in slower meshing and a higher polygon count with more equilateral and nicely shaped polygons. This is approximately the maximum aspect ratio of the quads in the Minimum initial grid quads. Setting Maximum aspect ratio to zero turns off the option. Zero means no limit.
The default value for this option is zero and the suggested range, when not zero, is from 1 to 100. This setting is scale independent.
When shading long, skinny objects, use 0.0 for the value. This allows infinite ratios. Control the smoothness of the mesh with other parameters.
If an edge is shorter than the Minimum edge length, the mesh face is not divided further. This is also, approximately, the minimum edge length of the quads in the Minimum initial grid quads.
The default value for this option is 0.0001 units and the usable range depends on the model size. Bigger values result in faster meshing, less accurate meshes, and a lower polygon count. Setting this value to zero turns off the minimum edge length option.
This option is scale dependent. The value is always in the current unit system.
Polygons are further divided until all polygon edges are shorter than this value. This is also, approximately, the maximum edge length of the quads in the Minimum initial grid quads.
Smaller values result in slower meshing and a higher polygon count with more equally sized polygons. Setting this value to zero turns off the option.
The default value is zero and the usable range depends on the model size. This option is scale dependent.
Polygons divide until the distance from a polygon edge midpoint to the NURBS surface is smaller than this value. This distance is also the approximate maximum distance from polygon edge midpoints to the NURBS surface in the Minimum initial grid quads.
Smaller values result in slower meshing, more accurate meshes, and a higher polygon count. Setting this value to zero turns off the option.
The default value is zero and the usable range depends on the size of the model.
Use as a general polygon mesh tolerance setting.
The number of quadrangles per surface in the initial mesh grid. This is the first stage of meshing. Rhino splits the surface into the number of rectangles you input. From this point, Rhino can either refine the mesh by checking the other parameters. If necessary, it splits the rectangles.
Rhino uses at least as many polygons as you designated and maybe more.
Bigger values result in more evenly distributed polygons, but slower meshing. The suggested range is from 0 to 10000. To turn off, set the value to zero.
After its initial meshing, Rhino uses a recursive process to refine the mesh until it meets the criteria defined by Maximum angle, Minimum edge length, Maximum edge length, and Maximum distance, edge to surface options.
The mesh is refined until the angle between surface normals along a polygon edge is smaller than this value. The default is 20 degrees and the suggested range is from 5 to 90 degrees. Setting Maximum angle to 0 turns off the option. It is scale independent.
No refinement results in faster meshing, less accurate meshes, and lower polygon count. If you clear this checkbox, untrimmed individual surfaces and surface areas away from trim edges and joined edges are meshed with evenly sized quadrangles.
All surfaces mesh independently and Rhino does not stitch the edges of joined surface edges together. Meshes for each surface in a polysurface do not necessary meet to form a watertight mesh. If Jagged seams is not checked, watertight meshes are created.
Checking Jagged Seams causes faster meshing, a lower polygon count and cracks between joined surfaces in the rendered image. Rhino does not support watertight quadrangle meshes unless you are meshing a single untrimmed surface. In this case, clear Refine mesh and use Jagged seams to generate quadrangle meshes.
All planar surfaces are meshed by meshing the surface edges and then filling the area bounded by the edges with triangles.
Simple planes causes a slower meshing and a minimum polygon count on planar surface, especially for complex trimmed surfaces.
If Simple planes is selected, the settings, except Jagged seams, are ignored for planar surfaces and the planar surface is meshed with as few polygons as possible.
Note: The meshes created by the Mesh command are visible and editable, and separate from the NURBS objects they were created from. The meshes created by Rendered Viewport and Shaded Viewport on NURBS surfaces and polysurfaces are invisible, not editable, and cannot be separated from the NURBS object, except to destroy them with the RefreshShade command. Render meshes are controlled by a different set of meshing settings, which are on the Document Properties dialog box Render page.