Brep vs nurbs

I have an STL file having surface mesh data. I would like to convert this into a volume mesh. Is there any such option in meshlab?

Any insight into this would be much appreciated. One of the best maybe. Well, I think i might have come to a partial solution, there is a software called mesh2solid. I am working on Biomechanics field and i need it since we can get only a surface mesh data from our "sources".

Also, is there any possibility of getting a volume mesh from Rhinoceros? I couldn't find it. The interface looked like a modeling one rather than a meshing software What do you exactly mean with "volume mesh"? A polyedral decomposition of the space enclosed by a triangulated surface? A tetrahedral decomposition? In that case MeshLab is not the best tool, because it is oriented to the management of surfaces and not volumetric representation.

Seems I came close Beware: It keeps the faceted outline. If you just want to to Booleans - by any means - use Blender or Art of Illusion. Rhino can do both - Mesh and Nurbs- Surfaces and a little bit of Solids. You should be able to read in STL and there are plugins you can load as trial that helps you reengineering the surface data to nurbs and solids in case of watertight surfaces of course.

But even then: What exactly are you going to do in your "biomech" field with the data? With knowing the exact goal people here might be able to serve and help you better In the field i work, there are companies that provide the surface meshes of a part of the human body, lets say the pelvic bone. These are given as an STL file mesh. And we would like to have them as a solid volume.

So, i began to hunt for some software that converts a surface mesh into a solid. I tried the trial version of Rhino but couldn't find any option for this kind of a conversion. We would buy the full version if only i could be sure that Rhino could do this.

And yes, all the surfaces I am talking about are watertight indeed. Thanks all :. But may I ask another time: What do you do with your "solid" meshes or better Breps in that case? Maybe there are free, open source or just better suited packages available I am also facing the this problem did any find the solution. Help Create Join Login. Operations Management.Skip to main content. Autodesk Knowledge Network. Fusion Learn Troubleshooting Forums.

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The MeshToNurb Command

Issue: You have imported a mesh file. STL or. OBJ into Fusion and you would like to convert it to a solid body to edit.

brep vs nurbs

Causes: Mesh to BRep is only available if you are not capturing design history. Mesh files can be difficult to work with when adding features such as holes or extruded cuts compared to solid b-rep bodies. If your mesh body contains more than 10, facets, it is possible the conversion process will fail or errors will occur.

To convert a mesh body to a b-rep body in Fusionyou must be working in the direct modeling environment at least temporarily. If you would like to work with the design timeline enabled after inserting and converting a mesh, you can insert the mesh as a base feature. If you plan on working in direct modeling after inserting the mesh, you can simply disable the design timeline.

To enter direct modeling mode and convert a mesh body to a solid B-Rep: Click the gear icon in the bottom right hand corner of Fusion and select Do Not Capture Design History. This removes the design timeline and enters Direct Modeling mode. Find related content. Get answers fast from Autodesk support staff and product experts in the forums. Visit Fusion Forums. Need Help? Tell us about your issue and find the best support option.

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Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. We need to discuss the scope for the applicable geometries to be included in the IFC4 Reference View.

HI, i suggest to keep it as simple and reliable as possible. I ran some numbers on files sizes and memory usage, and put together a PowerPoint with the findings:. The benefit of tessellation is clear for arbitrary mesh geometry e.

027 Differences between NURBS and polygons

Now the benefit also seems clear where occurrences have varying geometry such as the scenarios tested. Though are these scenarios representative? Can anybody propose other typical scenarios? Thank you for your excellent presentation. Overall, it is good, but I think there are a few issues with it. One other thing to consider: There is a separate workflows for handover and reference.

NURBS vs. Polygons

However, many times the need is mixed. The sender do not know whether the model is used also for handover purposes. It would be advantageous to combine these two workflows to a single IFC model.

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In IFC4 this is now possible. Data loss is not acceptable. As an end-user I strongly agree with Lassis' point regarding accuracy. Perhaps if it were a mandatory cert. Great points here. For those scenarios tested, some underlying assumptions were made, which may not necessarily hold true across different building types and application software.

A The idealized scenario assumes that there is only one geometric model of a given pipe cross section, and occurrences use IfcMappedItem with non-uniform scaling along axis of pipe -- similarly to how IfcExtrudedAreaSolid can refer to a shared IfcCircleHollowProfileDef and each IfcExtrudedAreaSolid has different length and positioning.

Going further, if the thickness of the pipe doesn't matter, then pipes of all sizes could refer to the same cylinder being able to scale the radius and the length for all mapped geometry.

The same assumption is made for pipe bends -- there would be a single representation for each pipe radius and bend angle 45, 90, etc.

B Another assumption made here is that pipes and pipe segments are represented by primitive geometry that can be scaled without taking into account flanges, etc. For smaller pipes, perhaps this is good enough; for larger ones, perhaps not. If ends of pipes need to be modelled specifically, then that would also need to be taken into account either tessellation or in some cases NURBS to be modelled exactly. C Another assumption is that implementations make optimized conversions to mapped geometry, which they may already be doing internally -- rather than translating IfcSweptDiskSolid into IfcTriangulatedFaceSet, implementations would use the underlying reference curve and generate IfcMappedItem for each segment i.

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D Stepping back, use of tessellation for anything curved sort of implies that a tradeoff is made where accuracy is compromised. Perhaps we should define the required uses of the Reference View -- e. Should the Reference View require a particular tolerance? Should such tolerance be declared in files such that apps or users can determine if adequate for the intended use?

Perhaps some applications could give the user control over accuracy? I would assume most clash detection algorithms ultimately reduce down to intersection of triangles after narrowing down efficiently based on space partitioningrather than using exact mathematical formulas. Also, what other uses are foreseen of the Reference View?It is defined internally as a list of vertices points and faces each face connects either three or four vertices. Meshes also support per vertex normals and colours, as well as a host of other properties.

brep vs nurbs

A surface is, well, a surface. It consists of a single smooth area but may have custom edges. A brep is one or more surfaces joined together. If a brep only contains a single face, then it is the same thing as a surface.

For surfaces to be joined together into a brep, they need to share some of their edges. This consensus is what makes me wonder, why even work in surfaces if meshes are superior in compute time? What are the advantages and disadvantages of both?

Surface data is a set of numbers which can be used in a formula to determine the coordinates of a point anywhere on a surface. Also the direction perpendicular to the surface, the curvature of the surface and other characteristics can be determined anywhere on a surface. A mesh is a set of points called vertices, and information about how the vertices are linked.

By itself a mesh does not define anything between the vertices. There are other schemes such as sub-sivision for filling the spaces between mesh vertices. Repeat sub-division repeatedly and the set of points approaches a surface. However sub-division generally offers only limited control over the resulting shape.

Whether a mesh or a surface is better or faster depends on the task and the geometry involved. Meshes are inherently faster for the computations involved in displaying geometry on a screen. Rhino creates a display mesh whenever a surface is to be displayed. The display mesh is automatically updated when the surface is changed. Meshes may be easier to use to model a complex shape such as a face, plant or rock.

Surfaces are usually better if smooth surfaces or geometric shapes are involved, such as automobiles furniture, boats, aircraft, consumer products. Accurate modeling is usually easier with surfaces. Surfaces also provide any desired level of control of the shape.

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Operations such as intersection or trimming can be simpler due to the inherent ability to calculate the coordinates anywhere on a surface. Such operations with meshes usually use the faces which is equivalent to using a set of simple surfaces.

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Creating a mesh from a surface, even a complex surface, is computationally simple or even trivial, and is easy to automate. Creating a complex surface from a mesh can take orders of magnitude more computations and may require significant human intervention.

Distinctions between meshes and surfaces becomes somewhat blurred for planar surfaces and faceted shapes. Perhaps an edit would be useful.Sue passed away in late April from an aggressive form of cancer. I know many of you enjoyed working with her to solve your issues. She was a tremendous asset to our company and will be greatly missed. She worked for us for about 10 years. Sue contributed greatly to the usability of our products and their professional look. We will all miss you Sue!

Power Surfacing 5. This is a major upgrade with many new features in RE. See the 5. Power Surfacing 4. This is a major upgrade with many new features. See our partner page here. See the press release here. Read more. Sub-D modeling excels at producing and modifying complex, freeform organic shapes with smooth surfaces, explains the company, while NURBS modeling is good at combining shapes using Boolean and feature operations, as well as refining shapes with operations like filleting, blending, and face editing.

Power Surfacing uses a hybrid modeling kernel to bridge the gap between freeform modeling and CAD's geometric precision. Let me introduce you to a soon to be released product. Power Surfacing. Your SDS model becomes a feature in the tree. Power Translators Universal.Hi, Can anybody tell me the differences between these classes?

My problem is I load a surface a polygon with a hole on it as brep in GH, then I want to get this surface in GeometryBase type. It seems I can only get a solid polygon, the hole is missing. I have tried to get a surface first by x. Faces[0], it is a brepFace, displayed as something like a plane. Share Tweet Facebook Facebook.

Views: GeometryBase is an abstract class that unifies as many functions and properties as makes sense that apply to all geometry everywhere.

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Curves, Points, Surfaces, Meshes, you name it. This is useful because now all geometry can derive from GeometryBase making the things they have in common a matter of definition. Surface is another abstract class that unifies as many functions and properties as it can that apply to all surfaces. All surfaces have an area for example. And they all have U and V domains.

Rhino supports a number of different surface definitions, among which are PlaneSurfaces filled rectangles, basicallyRevSurfaces revolutions of a curve about an axisSumSurfaces one curve is moved along another and NurbsSurfaces. NurbsSurface is a non-abstract class that derives from Surface and therefore also from GeometryBase which implements the mathematics of Nurbs surfaces.

So every NurbsSurface has control-points, knot-vectors and so on and so forth in addition to whatever Surface already defines. For example a Box would need to be a Brep because it contains 6 surfaces that are joined at their edges. The filled letter O would also need to be a Brep since it has trim curves that remove portions of a surface. A Brep maintains many lists of geometric entities, including faces, edges, trims, loops and vertices. All of these are associated with each other via topological relationships.

Brep is a very complicated class so don't worry if you don't understand how it works.

brep vs nurbs

BrepFace represents a single surface in a Brep.In solid modeling and computer-aided designboundary representation —often abbreviated as B-rep or BREP —is a method for representing shapes using the limits. A solid is represented as a collection of connected surface elements, the boundary between solid and non-solid. Boundary representation of models are composed of two parts: topology and geometry surfaces, curves and points.

The main topological items are: facesedges and vertices. A face is a bounded portion of a surface ; an edge is a bounded piece of a curve and a vertex lies at a point.

Other elements are the shell a set of connected facesthe loop a circuit of edges bounding a face and loop-edge links also known as winged edge links or half-edges which are used to create the edge circuits. The edges are like the edges of a table, bounding a surface portion.

Compared to the constructive solid geometry CSG representation, which uses only primitive objects and Boolean operations to combine them, boundary representation is more flexible and has a much richer operation set. In addition to the Boolean operations, B-rep has extrusion or sweepingchamferblending, drafting, shelling, tweaking and other operations which make use of these. Baumgart at Stanford for computer vision.

How to convert a mesh to a BRep in Fusion 360

Braid continued his work with the research solid modeller BUILD which was the forerunner of many research and commercial solid modelling systems. Following Braid's work for solids, a Swedish team led by Professor Torsten Kjellberg, developed the philosophy and methods for working with hybrid models, wire-frames, sheet objects and volumetric models during the early s. Initially CSG was used by several commercial systems because it was easier to implement.

Boundary representation is essentially a local representation connecting faces, edges and vertices. An extension of this was to group sub-elements of the shape into logical units called geometric featuresor simply features. Features are the basis of many other developments, allowing high-level "geometric reasoning" about shape for comparison, process-planning, manufacturing, etc.

Boundary representation has also been extended to allow special, non-solid model types called non-manifold models. As described by Braid, normal solids found in nature have the property that, at every point on the boundary, a small enough sphere around the point is divided into two pieces, one inside and one outside the object. An important sub-class of non-manifold models are sheet objects which are used to represent thin-plate objects and integrate surface modelling into a solid modelling environment.

The common generic topological and geometric models are defined in ISO Geometric and topological representation. The following Application Integrated Resources AICs define boundary models that are constraints of the generic geometric and topological capabilities:. Further information about Boundary Representation can be found in a variety of papers and the following books:.

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