Strange effect when bridging loops

PilotFerdi · September 23, 2020, 6:36pm

I’m trying to create a hole in a plane, pretty basic stuff. The steps I took are the following (please see attached images):

Create the plane;
Subdivide the edges;
Delete the required center vertices (rectangular hole in the plane):

Add a circle with the same number of vertices/edges:

Select the two edge loops;
Apply “Bridge Edge Loops”:

The result is a weird bridging, and no matter how I rotate the circle (X, Y, or Z) it doesn’t come out right:

Please help me understand: What did I do wrong? How can I correct it?

Thank you for your consideration!

Lumpengnom · September 23, 2020, 7:24pm

Try the “twist” parameter in the Bridge Edge loops menu.

PilotFerdi · September 24, 2020, 2:59am

Try the “twist” parameter in the Bridge Edge loops menu.

Thanks, Lumpengnom! I tried - it worked, albeit not by itself. However,

twisting a certain amount (in this case, Twist: -24) until the vertical vertices became aligned, albeit crisscrossed;
selecting only the circle, and
rotate 180 degrees around X-axis

did the trick. (NOTE: the alignment can be done on horizontal vertices, too, with the Y-axis as rotation axis.)
Please see the results below:

Any idea why this happened? I’ve made holes in planes before (true, with fewer vertices), and never had this problem.

Also, what can I do to prevent this issue in the future?

Warm regards.

a59303 · September 24, 2020, 6:10am

This appears to have to do with this, not sure why.

This seems to work:

Hope that helps.

PilotFerdi · September 24, 2020, 7:25am

Thanks a59303! Your solution works beautifully, and, IMHO, much cleaner than twisting (which must be attempted several time until the vertices align properly)

It also helps to understand why it behaves so - it’s right there in the ticket: “The Bridge Tool calculates the wrong direction for the start and end points in different situations.” The response of one of the developers was that exactly side-by-side edge loops are not supported. (Huh??)

From a developer standpoint, I would check the math formulae or the flowchart that were applied to the bridge function. However, from our (i.e., users) standpoint, this is a bug, and we can work around it (for now) with some little hacks, like the twist + rotate, or the one you provided: offset between the edge loops (since side-by-side loops aren’t supported).

Again, much appreciated for shedding light on the problem, and providing a solution.

Warm regards.

a59303 · September 24, 2020, 7:04pm

Great. I couldn’t actually get a reliable solution the way you were doing it so I had to try something different. I also don’t get the developers explanation.

Greets.