Need help with topology

[Anonymous]

Hi,

I am trying to model this container in Fusion360. My problem is the detail in the red triangle.  

The original model was made using NURBS. I can make the basic shape in Tspline but I haven't manage to make the detail in the red triangle. I just don´t know what is the right work flow to accomplish it. Can any one give me a hint?

Thanks

Ricardo

[innovatenate]

Hi Ricardo,

Welcome to the Fusion 360 forum! I was wondering if you could share a file or some more screenshots of different angles.

Thanks,

[deyop]

That is a tricky shape.  I tried several approaches with T-Splines alone but found the difficulty was finding a satisfactory result as the feature moved from the top of the surface to the front.  I exaggerated the issue in image 2 below but this is the basic problem to solve.  I tried a different approach by Thickening the basic shape with the "No Edge" option and then modifying the internal T-Spline shape. I then made a ribbon of T-Spline faces and placed it where the transition was.  I thickened that as well to get another trim edge and converted them all. 

In the Patch workspace I used the Split Body command and trimmed back the inside and outside so that there was a gap between them.  Then with the Loft command I bridged the gap between them.

I am not 100 percent satisfied with the results but I think the approach could work.  I would love to see if anyone has a T-Spline method that would address this case.

Developers are researching some solutions that allow transitioning across the grid of the T-Spline surface but that is still in development.

[innovatenate]

I agree this is a tricky shape.

I think unwelding some edges and then rejoining T-spline surfaces together may get closer. The results are unimpressive admittedly, but I wanted to share the approach anyway. Maybe this will inspire some other ideas! See the attached word doc.

Thanks,

[deyop]

Here is another approach.  Tom Finnigan helped me find this solution.  There are three separate areas that I created from a cylinder to start.  Then I split separate copies of the cylinder and broke them into pieces.  In the illustration the highlighted yellow line is where I extruded Local to create a band of faces around the edge.  I then used Merge Edges to snap a portion of the band of faces to the lower portion.  I did the same with the portions of the front. This left the five side hole to fill.  I used Create Face with the option for Multiple Sides to fill the hole that was left. 

I am not certain about how you were expecting to remove that dark portion from your picture but it looks like a Boolean of a cone shape from the rest of the form.   I think this is a usable strategy for the portion you highlighted in your picture.

[Anonymous]

Thank all of you for the feed back.

I tried the last approach and is looking good. However, I am having a hard time filling the gap between the two main surfaces. If I use the blend command I got a crease on one side ruining the round shape. I am attaching the file.

Ricardo

[deyop]

The reason the crease is forming is because there is an inside corner created by the break at the bottom of your form.  As the faces are filled in or you connect vertices together the smooth shape will return.  You can learn some more about this behavior in the Learning Area " Why did my model turn boxy".

In order to keep that circular form you may need to insert more edges to isolate the inset from the circular shape.  During yesterday's hangout there was a lot of discussion about how T-Junctions and Star Points are used to isolate form changes.  I will get the video recording information for you.

[cekuhnen]

Hey Ricardo,

you are already on a good direction, however think about redirecting the flow of loops as an additional tool for modeling.

But keep in mind that polygon modeling has a disadvantage of placing details locally an area NURBS is perfect for. However organic shapes and transitions are drasticaly easier with polygones in T-Splines.

Like pointed out a good idea and how I work is using each for what they are best for. In the image below I only put in certain details and the rest I would only touch up with NURBS. But playing through ideas for the body styling was a matter of few point and clicks commands compared to labor intensive re networking of a NURBS model in Alias Automotive.

Best

Claas

[deyop]

Claas, Thanks for those insights. Much appreciated.