MODELLING CONCEPTS
Ridge clusters.
A ridge cluster is a set of six vertices which begin a change of direction (normally inside a boundary). The angles between some of the vertices which are naturally created during extrusion with scaling along a plane, create an arrangement of angles which are not well interpreted by the subdivision surface modifier and need to be fixed.
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A corner vertex and the two vertices to either side of it form the top of a ridge cluster and these are normally left in place. The three vertices that these are directly connected to in the direction of a boundary edge. They are normally fixed before control loops for that boundary are inserted.
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![A ridge cluster on a blender mesh](https://static.wixstatic.com/media/288aaf_544d384199fe4d219cd2b871a9b7e702~mv2.jpg/v1/fill/w_600,h_337,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Ridge%20Cluster.jpg)
A Ridge Cluster
![A fixed ridge cluster on a blender mesh](https://static.wixstatic.com/media/288aaf_5d49f7c815de4b008f283ff4859a7ba0~mv2.jpg/v1/fill/w_600,h_337,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Ridge%20Cluster%20Fixed.jpg)
A fixed Ridge Cluster
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The two vertices at the outside are normally placed incorrectly during an extrusion and need to be moved until they are perpendicular to the top vertices in the cluster.
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You can see a (probably much clearer!) demonstration of this exact process when we create The King for the chess set.
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If they are not fixed, a thin ridge will be apparent in renders and the general spacing of your vertices will not be optimal for deformation and general use.
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Ridge clusters can also be used to your benefit in recreating shapes and ridges often seen in architectural design!
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