Problem understanding T-Spline topology problem

[cyangaze]

Hi,

I'm stuck on figuring out where the problem lies with the topology in this file and as a consequence I can't move to render.  The utilities repair body doesn't show any red stars or other errors that I can see, and autorepair doesn't seem to change anything.  I'm guessing there may be an issue with extra edges but I can't actually delete all asymmetrical edges without deleting faces and whenever I do delete faces to start over again, the bridge option just creates way more subdivisions.  I know in Blender I can easily dissolve edges and create single faces, but I can't seem to figure out how to do that here.  Anyway, please let me know what I am doing wrong.

I have attached the file.

Thanks

[TrippyLighting]

You can double click on an edge loop and hit the delete key to "dissolve" it.

The bridge command allows you to adjust the number of segments/edge loops you want bridge with 😉

You can insert edges where needed, and you can also slide edges just as you can in Blender.

You can even bevel edges, even though I believe this functionality is buggy at the moment.

[cyangaze]

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@TrippyLighting wrote:

You can double click on an edge loop and hit the delete key to "dissolve" it.

The bridge command allows you to adjust the number of segments/edge loops you want bridge with 😉

You can insert edges where needed, and you can also slide edges just as you can in Blender.

You can even bevel edges, even though I believe this functionality is buggy at the moment.

---

Yep I figured out how to select and delete edges, but sometimes they still end up deleting a face for me.  However, I was able to close and open the file again and I could delete the unwanted edges.  Thanks for the tip on the number faces in bridge...didn't even see it was set to 3 automatically.

However, even though I was able to figure these out, it still won't convert to render.  The message now says "invalid surface".  And I didn't see any errors in Repair Body.

[laughingcreek · Accepted solution]

There is a lot of weirdness at the front corner of the cushion.  That's readily apparent if you uncrease all the edges, and then look for edges with a heaver line (creased lines and boarder edges look the same on a t-spline.)  Here is a screen cast of finding the problem area.

You could try to untangle this area, but I would just delete it and rebuild it.

General t-spline rules of thumb-

-work in box mode most of the time (alt1)

-only use as many faces as you need (you have way more here than you need)

-avoid triangles

-place star points at relatively flat/low curvature areas 

[TrippyLighting]

This is one of those objects I would not build in Fusion 360, at least not at the start.

The ability to have edge weighting such as in Blender would make this a snap to model in blender with absolutely minimal  polygon count.

Edge weighting is one of those things that T-SPLines would tremendously benefit from

To the tips that @laughingcreek posted (and to which I agree 100%) I would add to never model with a crease applied.

If you need a crease, then do it when you are done editing.

If you continue to model with creases the internal tangent handles of the T-Spline (no accessible to the user) it will lead to undesirable behavior that can only be fixed y exporting and re-importing the T-Spline control cage.

[cyangaze]

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@laughingcreek wrote:

There is a lot of weirdness at the front corner of the cushion.  That's readily apparent if you uncrease all the edges, and then look for edges with a heaver line (creased lines and boarder edges look the same on a t-spline.)  Here is a screen cast of finding the problem area.

You could try to untangle this area, but I would just delete it and rebuild it.

General t-spline rules of thumb-

-work in box mode most of the time (alt1)

-only use as many faces as you need (you have way more here than you need)

-avoid triangles

-place star points at relatively flat/low curvature areas 

---

Thanks it totally worked!  Really great tips I never knew about (unfortunately there appears to be way less tutorials out there that talk about sculpting in Fusion, let alone topology so this has been really needed.  I uncreased everything, found a heavy edge, found the face you showed (as well as some other surrounding ones) and bridged the faces one by one until it was sealed again and worked in the render mode.  I will try to delete as many unnecessary edges as well.

[cyangaze]

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@TrippyLighting wrote:

This is one of those objects I would not build in Fusion 360, at least not at the start.

The ability to have edge weighting such as in Blender would make this a snap to model in blender with absolutely minimal  polygon count.

Edge weighting is one of those things that T-SPLines would tremendously benefit from

To the tips that @laughingcreek posted (and to which I agree 100%) I would add to never model with a crease applied.

If you need a crease, then do it when you are done editing.

If you continue to model with creases the internal tangent handles of the T-Spline (no accessible to the user) it will lead to undesirable behavior that can only be fixed y exporting and re-importing the T-Spline control cage.

---

Actually it's funny I modeled this a while ago in Blender and it's taken me a few months of learning Fusion to get to the point where I could model it in sculpt using similar methods.  The reason I used Fusion was because I couldn't accurately export the model for CAD and real world dimensions are not user friendly in Blender (IMO).  Agreed though, using creases during editing is bad practice.  Too bad there isn't a subsurf option where you could use loop cuts to tighten edges and keep the poly count down.

[TrippyLighting]

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@cyangaze wrote:

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  The reason I used Fusion was because I couldn't accurately export the model for CAD and real world dimensions are not user friendly in Blender (IMO).  

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Maybe not "user friendly" but perfectly accurate. I often stat something in Fusion 360 move it to Blender and then move it back to Fusion 360. Makes for a very powerful combo!