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rhino:diagnostics [2016/05/02]
 rhino:diagnostics [2020/08/14] (current)
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 +======Diagnosing Bad Geometry======
 +
 +>This information is buried in deep Rhino F1 help. Here it is brought up to the light.
 +
 +Sometimes a model can become damaged and the damaged areas can cause problems.
 +
 +It is possible to build bad models using Rhino tools. For instance, if you trim a surface with a self-intersecting curve, Rhino will let you do it, but the result will be a poorly defined model that causes problems later.
 +
 +Another problem is having a tiny, trimming edge that then gets joined to a larger trim curve on an adjacent surface. If Rhino matches the large edges, sometimes the tiny trim curve edge can get compressed even further so that it is really just a point. That compressed edge no longer has a meaningful orientation and causes problems.
 +
 +There are modeling techniques you can use to increase the robustness of your models.
 +
 +Drawing tiny little lines to connect pieces of a trim curve instead of moving the two endpoints of the curves together generally messes up joining other edges together and tends to cause problems.
 +
 +Sometimes the microscopic edges can be generated through other means, like Booleans where the objects are just off from each other by a little bit.
 +
 +Trimming edges that are very small or curved back on themselves are the biggest cause of problems in models.
 +
 +There are Rhino tools you can use to examine your model for these defects.
 +
 +The first one to try is the **Check** command. If your model doesn't pass **Check**, then it will list some specific problems. The list shows where you might tune up the model. If a model passes **Check**, it doesn't automatically mean that it is 100% properly structured, though. Some bad model parts, like having surfaces that fold back on themselves or self-intersect, are very time consuming and difficult to automatically detect. **Check** doesn't check for those things, but it can check the general overall structure of the object.
 +
 +The workaround is to **Explode**, **Untrim**, **Trim** again, and **Join**. If there are lots of tiny edges, then you may need to use the **SplitEdge** command to split all edges so they have a compatible structure, and then use **JoinEdge** to manually mate the proper pairs.
 +
 +When there are long things and tiny things next to each other, the **Join** command can get confused. When that happens, the low level manual **JoinEdge** can work as a replacement.
 +
 +These tools are on the **Analyze** menu under **Edge Tools**. You may need to use several of these tools to fix difficult broken models as well.
 +
 +===Avoiding modeling errors===
 +
 +  * In general, try to avoid creating tiny edges in models.
 +  * Do not use curves where there is a tiny line in the middle of the curve that joins two pieces together.
 +  * Try to make sure that adjacent parts mate cleanly with a good, simple edge-to-edge matching.
 +
 +You can …
 +  * List data structure of an object
 +  * Check objects
 +  * Select bad objects
 +
 +
  

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