Both sides of sword blade get painted simultaneously . Why?

[justaviking]

I have a model of a sword.
When I paint on the blade, both sides get painted at the same time.

This came from a blender model.  It paints each side individually fine inside Blender.
I am including both the .blend and .obj files.

I wanted to engrave a name on the blade, but I get the mirror image on the other side of the blade, so that's not acceptable.

I'm told that no mirroring options were used in Blender (I didn't make the model), but it sure behaves that way.  The UV map looks okay, though.

Can anyone figure out what might be wrong?

P.S.
This started as a file someone gave me, and I think it came from Sketchup.
It behaved oddly.  There were some "distorted" facets in addition to this "mirror-image" painting.
I had my son re-create it from scratch in Blender, but I'm still getting this strange behavior even on the brand new model.

P.P.S.
When you open a mesh, it displays the .blend file, as if you could open it like you do a .obj file, but SP crashes if you try and open the blender file directly.

ATTACHMENTS:
1&2) ReModeling... the blender and obj files for the re-created sword.  This should be a clean model.  This is the one I really care about.
3) ReUnwrapping... the original Sketchup model, put into Blender to make a better UV map.  You can see the strange distortions on the blade edge, and it also has the issue where it paints both sides of the blade at the same time.  This is of less concern to me, but if anyone can figure out why the blade looks strange (but looks okay when imported into Blender) I'd love to learn.

[Malo]

The problem is the brush size.
A bigger brushradius paint through the thin blade.

Make a simple test, radius with 0.1 dont paint throug a radius with 2.0 paint through.
Maybe you need a option that ignores the backfaces, but i am not sure if this is implementet in SP.

[justaviking]

THANK YOU!   

I would never have guessed that, but it fixed it.

I purposely used a larger brush, especially when I was using a stencil to engrave a name onto the sword.
Somewhere around size 5 it starts to do the "both sides" behavior (on the blade of this model).

It really makes no sense to me.  It wasn't bleeding around the edges (it wasn't wrapping around the blade).

Seems like a bug to me, but at least I now have a workaround.

Thanks again.

[michael_11]

Would be great, if Allegorithmic would adress this issue; This would be a great implementation for the 2D view - painting ONLY in 2D view (due to the nature of UV´s, avoiding painting backfaces).

For me this is a problem with SP that makes it almost unusable for now. I used a workaround by separating thin geometry parts, but this is too tedious for production.

[Jeremie Noguer]

If you switch your paint Alignment (in the advanced options of your current tool) to Camera or UV, does it fix the issue?

[justaviking]

Camera = No improvement.

UV = Works great, even with a large brush size.

I still consider this a bug.  Why would "Tangent" and "Camera" paint THROUGH your object to the back side?  Even a brush that is smaller than the sword blade width can still paint through.  If it bled over the edges, it might make sense to me, but it goes right through the middle of the blade to the other side.

This behavior might make an interesting tool option.  "Paint through" or "paint back faces too" or something like that.  But in my opinion, it should never paint the back faces, unless I told it to do that.

THANKS for the second fix.  This one is better for me.

[michael_11]

If you switch your paint Alignment (in the advanced options of your current tool) to Camera or UV, does it fix the issue?

thanks for the hint!

[i.woitas]

I got the same "error". I also use Blender for my models. I made a medieval well with a roof. The painting works great on very part of the model, except the roof. And the roof is not as thin as a sword. It stops by a brush size below 8. Also the paint Alignment with UV works. But I also think (hope), that this is just a workaround and not the solution.

[Jeremie Noguer]

We will add an option to disable backface painting at some point.

[kevintraywick@gmail.com]

Helpful topic. I had the same problem but thought it was a bug in symmetry. Painting alignment doesn't fix it but I'll try a different brush size and see if that does it. Thanks,Kevin

[justaviking]

We will add an option to disable backface painting at some point.

Awesome.  Thank you.

I humbly suggest that "Backface Painting = Disabled" should be the DEFAULT setting.

[nickzucc]

I personally want the option to paint straight through the model and have an option to mask the model as it faces away from the camera. Both are important to me!

[justaviking]

I personally want the option to paint straight through the model and have an option to mask the model as it faces away from the camera. Both are important to me!

Agreed.  I can see both options being useful.

I think of the models as "solid," so having paint appear on the back side came as a surprise (the bad kind of surprise).  That doesn't happen to me when I paint my walls at home.

So that's why I propose "Backface Painting = Off" as the default, with the option to turn it on when desired.

[cesar3dartist]

I used MARI for a long time, and I'm now using Substance for the first time. MARI has an option to define the back/front painting of polygons, but it is also set ON by default. It should be OFF in my opinion.

Substance should also make use of a curve in order to define the profile of polygons to be painted, in relation to the camera. For example, you can then avoid painting the sides of polygons NOT facing the camera. THis transition could be smooth, or could be sharp. This will depend on the gradient used and defined by the user on the interface. Check at the MARI implementation. It works great for doing architectual work that has lots of geometrical shapes, where you want to really just paint specific areas without smudging the sides.

It feels good to be a total noob in painter.