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help with obj file

Question asked by Sajjan Kc on Oct 8, 2014
Latest reply on Oct 9, 2014 by Chris Dordoni

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Hi everyone,

I am new to the forum but have used solidworks in my school. I am a recent graduate and am trying to learn more about SW. I hope i posted in the right place if not please direct me and i will post it accordingly.

I have downloaded a file from grabcad.com of a motorcycle which has .obj extension. How can i work with the file in SW?

I opened the file in SW and all i got is the following model which i cant break apart or see the parts involved.

I just want to see all the parts involved and get a better look as i am trying to rebuild a similar motorcycle in my garage.

Please help me to figure this out.

Thank you

Chris Dordoni Oct 8, 2014 3:18 PM

Correct Answer

hello,

An OBJ file consists of triangular facets, or quads (which are really two paired triangles). SolidWorks describes surfaces mathematically, not as a finite set of points, like a triangulated file.

Bringing a triangulated file into SolidWorks does not usually give you anything usable, except as a modeling reference. Each triangle gets converted into a surface, and you are limited to about 15,000 surfaces in a solid object (somewhat more if you have an open surface).

If you convert your OBJ to an STL (or VRML/WRL), you can import it, but if it has more than approx 15,000 triangles it will not import as a solid body (import options). You can try surface body, which will allow slightly more triangles. Using the graphics body import options will allow you to import with millions of triangles, but you wont be able to snap to any geometry or extract any geometry, so its useful only as a visual reference.

I think the best way to do this is use a program like Blender (free) that work with polygons or triangles and will let you view and easily hide or delete portions of the model so you can see the inner details.

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Chris Dordoni Oct 8, 2014 3:18 PM

hello,

An OBJ file consists of triangular facets, or quads (which are really two paired triangles). SolidWorks describes surfaces mathematically, not as a finite set of points, like a triangulated file.

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Sajjan Kc @ Chris Dordoni on Oct 8, 2014 4:03 PM

Thank you very much for the reply.

Honestly speaking, my knowledge of SW and how it works is very limited. I just have basic modeling experience and that is all. Could you please describe in detail if you don't mind what the following mean?

1.triangulated file

2. modeling reference

3. conversion of triangle to a surface

4. open surface

5. STL/VRML/WRL

6. Surface body

7. graphics body import option

Also i downloaded Blender which i have no prior experience with and having a tough time figuring it out too. I request for any knowledge that you can provide me with.

Please feel free to refer me to any other website or source for more information if you dont want to spend time explaining these details. I am very eager to learn about SW and i appreciate all the help.

Thank you.

Sajjan

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Chris Dordoni @ Sajjan Kc on Oct 9, 2014 12:35 AM

A triangulated file has surfaces that are broken into smaller pieces (triangles). If you get close enough to a curved surface that is triangulated, you can see the facets in a wire frame or flat shaded view, like the surface of a cut jewel. In SolidWorks, curved surfaces are smooth. If you look at a wireframe view, you will see the surface only in where it connects to another surface and the edges where the surface turns away from the viewing direction.

Modeling reference means the object is used to generate new surfaces in SolidWorks. This is done by drawing new curves or extracting curves/edges on an imported model, and then using the surfacing tools to build the object based on the curves.

Triangles become individual nurbs surfaces, so a triangulated sphere that looks smooth in another program might have 20,000 triangles. Usually this would be just one continuous smooth surface in SolidWorks.

An open surface is like a sheet of paper, you can fold it many times and its still open. It has two sides, and you can see both sides. A closed surface has only one side that you see, like a sphere or box. No matter how you turn it, you are still only seeing the outside. If you put a small hole in it, even one you can't easily see, and it does not connect to another surface (or another area on the surface in the case of the sphere) it becomes open. If the box is made out of material with thickness, like sheet metal or wood, you can put a hole in it and it can still be closed. The side of the hole closes off the inner and outer surfaces, so you are still seeing an outside surface if you look through the hole.

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Sajjan Kc @ Chris Dordoni on Oct 9, 2014 11:11 AM

Thank you again for the detailed reply.

I downloaded and imported the obj file with blender. I can move the parts with right clicking on them but it is a little finicky.

Any pointers on how i go on working on it with Blender?

Following is the image of what i am stuck with.

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Chris Dordoni @ Sajjan Kc on Oct 9, 2014 4:46 PM

It is possible the motorcycle was saved as a single object rather than a group of separate objects. If you can find the listing of the objects in the scene in Blender, and you only see the motorcycle object instead of a group of objects, then you will have to break it into pieces yourself.

You could check over on the Blender forums for more info. I don't use Blender, but most poly modelers have the tools to take a single object and separate it into different objects.

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5 Replies

Chris Dordoni Oct 8, 2014 3:18 PM
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Correct Answer
hello,

An OBJ file consists of triangular facets, or quads (which are really two paired triangles). SolidWorks describes surfaces mathematically, not as a finite set of points, like a triangulated file.

Bringing a triangulated file into SolidWorks does not usually give you anything usable, except as a modeling reference. Each triangle gets converted into a surface, and you are limited to about 15,000 surfaces in a solid object (somewhat more if you have an open surface).

If you convert your OBJ to an STL (or VRML/WRL), you can import it, but if it has more than approx 15,000 triangles it will not import as a solid body (import options). You can try surface body, which will allow slightly more triangles. Using the graphics body import options will allow you to import with millions of triangles, but you wont be able to snap to any geometry or extract any geometry, so its useful only as a visual reference.

I think the best way to do this is use a program like Blender (free) that work with polygons or triangles and will let you view and easily hide or delete portions of the model so you can see the inner details.
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- Sajjan Kc @ Chris Dordoni on Oct 8, 2014 4:03 PM
  Mark Correct
  Correct Answer
  Thank you very much for the reply.
  
  Honestly speaking, my knowledge of SW and how it works is very limited. I just have basic modeling experience and that is all. Could you please describe in detail if you don't mind what the following mean?
  
  1.triangulated file
  2. modeling reference
  3. conversion of triangle to a surface
  4. open surface
  5. STL/VRML/WRL
  6. Surface body
  7. graphics body import option
  
  Also i downloaded Blender which i have no prior experience with and having a tough time figuring it out too. I request for any knowledge that you can provide me with.
  
  Please feel free to refer me to any other website or source for more information if you dont want to spend time explaining these details. I am very eager to learn about SW and i appreciate all the help.
  Thank you.
  Sajjan
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  - Chris Dordoni @ Sajjan Kc on Oct 9, 2014 12:35 AM
    Mark Correct
    Correct Answer
    A triangulated file has surfaces that are broken into smaller pieces (triangles). If you get close enough to a curved surface that is triangulated, you can see the facets in a wire frame or flat shaded view, like the surface of a cut jewel. In SolidWorks, curved surfaces are smooth. If you look at a wireframe view, you will see the surface only in where it connects to another surface and the edges where the surface turns away from the viewing direction.
    
    Modeling reference means the object is used to generate new surfaces in SolidWorks. This is done by drawing new curves or extracting curves/edges on an imported model, and then using the surfacing tools to build the object based on the curves.
    
    Triangles become individual nurbs surfaces, so a triangulated sphere that looks smooth in another program might have 20,000 triangles. Usually this would be just one continuous smooth surface in SolidWorks.
    
    An open surface is like a sheet of paper, you can fold it many times and its still open. It has two sides, and you can see both sides. A closed surface has only one side that you see, like a sphere or box. No matter how you turn it, you are still only seeing the outside. If you put a small hole in it, even one you can't easily see, and it does not connect to another surface (or another area on the surface in the case of the sphere) it becomes open. If the box is made out of material with thickness, like sheet metal or wood, you can put a hole in it and it can still be closed. The side of the hole closes off the inner and outer surfaces, so you are still seeing an outside surface if you look through the hole.
    Like • Show 1 Like1
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    - Sajjan Kc @ Chris Dordoni on Oct 9, 2014 11:11 AM
      Mark Correct
      Correct Answer
      Thank you again for the detailed reply.
      
      I downloaded and imported the obj file with blender. I can move the parts with right clicking on them but it is a little finicky.
      Any pointers on how i go on working on it with Blender?
      Following is the image of what i am stuck with.
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      - Chris Dordoni @ Sajjan Kc on Oct 9, 2014 4:46 PM
        Mark Correct
        Correct Answer
        It is possible the motorcycle was saved as a single object rather than a group of separate objects. If you can find the listing of the objects in the scene in Blender, and you only see the motorcycle object instead of a group of objects, then you will have to break it into pieces yourself.
        
        You could check over on the Blender forums for more info. I don't use Blender, but most poly modelers have the tools to take a single object and separate it into different objects.
        Like • Show 0 Likes0
        Actions

help with obj file

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