I add the SUBSURF MODIFIER and then appeared some strange lines

Support Modeling
1

Hi:

I created a silhouette

I extruded to give it a volume

I created faces

I smoothed with SHADING: SMOOTH

I add the SUBSURF MODIFIER

and then appeared some strange lines in the right arm and leg…

Why?

Why does lines appear in the right arm and leg?

How can i remove it?

The left arm and leg are ok.

I attach the original blend file

One solution: slice the mesh in half

Delete the right side

Duplicate the left side

Rotate the left side

Join the original left with the rotated one

But I want to know why blender do that.

Can i remove it?

Can i avoid it in future mesh?

Thank you in advancecaso foro.blend (247 KB)caso foro.blend (247 KB)

caso_foro.png1000×300 15.6 KB

2

Hi, feesgo.

You have a problem in your mesh because some of the normals are facing the wrong direction.

To fix this problem Select all faces in edit mode and then click “Recalculate” under the normals tab.

You can also check the direction that the normals are facing in edit mode by clicking the display face normals button.

3

Man Candy is right. You need to recalculate normals. Select the whole mesh in Edit Mode with A and then hit CTRL+N. The lines will disappear.
Here:caso foro.(normals recalculated).blend (363 KB)