Modeling Steps in Rhino

Discussion in 'Software' started by YachtElements, Jan 11, 2020.

  1. YachtElements
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    YachtElements New Member

    I have been struggling with adding steps to a hull model in Rhino, and wondered if anyone had some suggestions. If I have to explode the surfaces on the solid (closed) model, I need to be able to close it back up easily afterwards. I have been using the Orca CFD software and requires a perfect closed surface or mesh.

    Thank you
    Marc
     
  2. DCockey
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    DCockey Senior Member

    How much experience do you have with Rhino? CAD modeling?
    Are you trying to inset steps into a hull and deck model? If you create a model of the steps with sides which extend beyond the hull and deck then you should be able to use either
    a) BooleanDifference
    b) Trim the hull and deck with the steps, Trim the steps with the hull and deck, and Join the results
    c) Intersect the hull and deck with the steps, use the intersection curves to Trim the hull and deck and the steps, and Join the results.
    If the model was closed (no naked edges) before exploding then Join should create a closed model. Problems with trimming and joining frequently result from coincident surfaces or bad parts.

    The Rhino forum is an excellent resource for help using Rhino. McNeel Forum https://discourse.mcneel.com/ Posting a file which contains the parts causing problems will help with an answer. General questions like the one above are difficult to answer.
     
  3. YachtElements
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    YachtElements New Member

    Hi David,
    I have been using the Boolean command for other components. I'm just having difficulties when it i a complex shape. I was just wondering if there was another way. I have only been using the command with surfaces and wondered if using a mesh would give different results.

    Thank you very much,
    Marc
     
  4. TANSL
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    TANSL Senior Member

    The combination of solid models with surfaces or the decomposition of solids on surfaces can result in objects difficult to understand and handle by Rhino (and other CAD programs). Try to build the model with the original objects, without mixing objects of different types. Boolean algebra, on the other hand, produces very good visual effects but greatly complicates the model. The simpler everything is, the better.
    I do not advise you to use the meshes, since determining the physical properties of the models created with them can be difficult.
     
  5. DCockey
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    DCockey Senior Member

    Perhaps it should be noted that TANSL is not a Rhino user.
    Rhino does not use "solid" objects like some other CAD systems. Instead in Rhino solid objects are modeled as a set of surfaces which are joined into a polysurface with no "naked" edges.
    I have no idea why Boolean algebra and visual effects are mentioned together in connection with Rhino. Perhaps there is a connection in some other software.

    Rhino has a set of Boolean commands which can be used with working with combinations of closed polysurfaces (and in some situations, open surfaces/polysurfaces) to create geometry with is the union, intersection or difference of the input geometry. The Boolean commands are essentially a semi-intelligent combination of Trim and Join, and are used for geometry creation and modification. Rhinoceros Help https://docs.mcneel.com/rhino/6mac/help/en-us/index.htm#seealso/sak_boolean.htm?Highlight=boolean The results are exactly the same as would be created using the Trim and Join commands. The results are not more complex.
    The Rhino analysis tools work with meshes as accurately as with NURBS surfaces. Perhaps the situation is different with other software.
     
  6. DCockey
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    DCockey Senior Member

    Meshes are not inherently less prone to Boolean problems in Rhino so I would find and fix the current problem rather than hope substituting a mesh for a NURBS surface will fix the problem. Typically the Boolean operation on the corresponding mesh will have the same problem.
    The Boolean commands are essentially a semi-intelligent combination of Trim and Join. The Boolean commands are essentially a semi-intelligent combination of Trim and Join. Rhinoceros Help https://docs.mcneel.com/rhino/6mac/help/en-us/index.htm#seealso/sak_boolean.htm?Highlight=boolean
    A first step in diagnosing a Boolean problem in Rhino is to Intersect the objects. The result should be a valid closed polycurve. If it is not then the cause needs to be found.

    One of the most common reason for Rhino Boolean commands fail is when two objects have surfaces which are coincident or almost coincident with each other. I'm assuming the Edge command was used to check for naked edges. Another possibility is a problem with the geometry of one of the objects.

    A frequent mistake new users of Rhino make is to assume the Boolean commands replace the need to learn to use Intersect, Split, Trim and Join.
     
  7. TANSL
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    TANSL Senior Member

    I have not said that Rhino uses solids. If I have said it, please tell me where and I will correct myself immediately.
    Nor have I said that Rhino working with meshes is not accurate. I say that extracting physical properties from a model of meshes, with Rhino, with AutoCAD or with any other program, can be difficult.
    Thank you for your always solicitous attention to what I say or what you think I say but, please, read well what I write and, if due to my little ease with the language, it is difficult to understand, I will gladly try to explain myself better. Not knowing how to explain myself in English is my problem, I know, that is why I can and I want to try to improve my expressions and my speech to make myself understand correctly.
     
  8. DCockey
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    DCockey Senior Member

    TANSL, I agree that you did not say "Rhino uses solids". I did not say that you said it. However you did talk about solids in responding to a question about modeling in Rhino. A reader of your response talking about solids may have concluded that Rhino uses solids. That is why I responded with the explanation that Rhino does not use solids.
     
  9. TANSL
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    TANSL Senior Member

    This is what the OP poses. I have interpreted that he has had, or will have, to decompose solids on surfaces. I suppose, since I, even if you don't believe it, I also know Rhino, that this decomposition has to be done before importing the model to Rhino. If I was wrong, you tell me and I will gladly rectify my statements.
    Even if you don't believe it, I'm not criticizing anything about Rhino. Just notice that, in summary, the more complicated we make the generation of a 3D model, the more difficult it will be to work with it. As, I think, you know, the model is only a tool to carry out some calculations. If that model, while being very beautiful, does not allow these calculations, it is useless. And that, simplicity, for me, is an axiom, talking about Rhino or any other CAD program.
    I repeat once again, as I do in each of the discussions I have with you, that I have nothing against Rhino. I simply indicate its limitations when I think it can be useful for the person who describes the problems he has with his 3D model. Fortunately I have experience in 3D molding with several software and I believe, I hope, to be able to help people with my observations. I have nothing against Rhino.
     
  10. DCockey
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    DCockey Senior Member

    Who said anything about importing a model into Rhino? I assume the OP created his model using Rhino and Orca3D (a Rhino plug-in). He did not mention using any other software.

    Perhaps you are confused by the OP's use of the term "solid (closed) model" in reference to his Rhino model and assumed he had imported a "solid model" as created by software such as SolidWorks. As I explained above in the Rhino world the word "solid" refers to a closed object which is made up of one or more surfaces which are joined together with no edges which are not joined to one other edge (no naked edges). That is the only way Rhino represents a solid object, and is sometimes refered to as a BRep model or Boundary Representation model.

    In contrast some other software such as SolidWorks software uses a fundamentally different mathematical formulation to directly represent some solid objects without using surfaces. It is true that when such a model is imported into Rhino the surfaces representing the boundary need to extracted to create a boundary representation model in Rhino. However the original question did not say anything about importing such a model into Rhino.

    Unfortunately that experience with other software has apparently lead to confusion about Rhino due to a lack of sufficient, relevant experience with Rhino.

    What limitation of Rhino do you believe is involved with he OP's problem?
     
  11. TANSL
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    TANSL Senior Member

    @DCockey, I strongly urge you to read carefully what I write before responding to my comments. If I explain myself badly, please tell me and I will try to improve my explanations. I do not say that the OP has said anything, what I say is that I suppose he had, or was going to have, a solid model that he wanted to break down into surfaces. That transformation, in my opinion, together with the mixture of solid objects and surfaces, in my opinion, can lead to difficulties. And I assumed that if that solid model, broken down on surfaces, is to be exòrted to Rhino, he could have difficulties.
    I really do not know how to explain myself better but I assure you that I do not say what you affirm that I have said. Please believe me, even though my experience with Rhino is not as big as yours. And, I also affirm that my much or little experience with Rhino does not take away or add validity to what I say.
    For me, our conversation is over since I will never say what you say I will say. So .... end of this story.
    Cheers.
     

  12. YachtElements
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    YachtElements New Member

    Thank you. @DCockey, Good advise. In my experience 80% of failures is because I find out there is a missing intersection. The other 20% I am still working on...
     
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