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BA_1157523810-Marble
10-Marble
July 30, 2025
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Struggling with surface that requires more than two intersections

  • July 30, 2025
  • 1 reply
  • 554 views

Hi everyone,

 

I'm a fairly new user, but I've been getting comfortable with most of the tools: using sketches, datums, and building surfaces. I've been working on a project and I'm stuck on one part that I’d really appreciate some guidance on.

 

I’m trying to model a back surface (see images below) that has a complex 3D curvature. I initially tried using the Intersect tool, but it didn’t give me the full shape I needed; it only creates sketches at the intersection of two surfaces, and this back surface seems to requires at least three reference surfaces or profiles to fully capture the curvature.

 

I’m trying to approach it using 3D sketches and datums to define guide curves and then generate a surface from those. I’d prefer this more parametric and controlled route over something like the Warp tool. But I haven’t found a clean way to do this yet. The curvature is irregular enough that I’m not sure how to lay out the sketches or organize the build sequence.

Has anyone tackled something similar or have suggestions for the best way to approach this kind of surface?

Thanks in advance!

BA_11575238_0-1753836408173.png

BA_11575238_1-1753836420328.png

BA_11575238_2-1753836657389.png

Currently using Creo Parametric 11.0.0.0

Best answer by tbraxton

A general best practice for this type of surface is to build a 4-sided surface (bounded by yellow curves) whenever possible. You can use the boundary blend feature with the 4 curves shown in red (#s) to get the surface. Curves 1&2 in direction 1 and curves 3&4 in direction 2. If you need additional control over the topology then you can add the two internal grey curves (blue #s) within the boundary blend feature.

 

For some geometries a variable section sweep can be used and may be preferred but I am not able to tell from your pictures.

 

Once you have the surface as required then trim the perimeter using construction surfaces or curves.

 

 

tbraxton_0-1753839113218.png

 

1 reply

tbraxton
22-Sapphire II
tbraxton22-Sapphire IIAnswer
22-Sapphire II
July 30, 2025

A general best practice for this type of surface is to build a 4-sided surface (bounded by yellow curves) whenever possible. You can use the boundary blend feature with the 4 curves shown in red (#s) to get the surface. Curves 1&2 in direction 1 and curves 3&4 in direction 2. If you need additional control over the topology then you can add the two internal grey curves (blue #s) within the boundary blend feature.

 

For some geometries a variable section sweep can be used and may be preferred but I am not able to tell from your pictures.

 

Once you have the surface as required then trim the perimeter using construction surfaces or curves.

 

 

tbraxton_0-1753839113218.png

 

    B
    BA_1157523810-MarbleAuthor
    10-Marble
    July 30, 2025

    Thanks for the reply!

    For orange curve 2 — do you have any suggestions on how to make sure its outward curvature consistently follows or mimics the shape of internal topology curve 2? I'm trying to maintain the same curvature relationship between the two. Or can the internal topology curve override curve 2?

    BA_11575238_0-1753851688483.png

     

    tbraxton
    22-Sapphire II
    tbraxton22-Sapphire II
    22-Sapphire II
    July 30, 2025

    Without a complete understanding of your design intent, I am speculating on how to best create the features. If you are using a commercial license of Creo then you can post the model here to be reviewed. If you are using a student license, then most here will not be able to open the file.

     

    If you build the internal curves before creating the boundary blend and then use those curves in the boundary blend feature, then the internal curves influence the geometry of the resulting surface. If you need to explicitly control the tangent vectors (proximal & distal) of the construction curves, then you would need to build them accordingly.

     

    You can control the continuity of this surface relative to parent geometry where needed. If you need to control this then make sure that the construction curves are built to support the level of surface continuity desired. The curves used to build the surface must have equal or greater continuity connections to that needed at a given surface boundary.

     

    Within the boundary blend feature UI you can access this optional function.

    Optionally, click the following tabs to further develop the boundary blend:
    ◦Constraints—Controls the boundary conditions including tangency conditions for edge alignment and side curve influence.
     
    Check out this video with details on boundary blend creation.
    https://www.youtube.com/watch?v=12CYdjy3LUk&t=9s 
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