Backfaces? (noob question)

Hello. In my WIP model, there’s some faces that are selectable and visible on the editing windows, but show up as black in renders. I suppose they’re backfaces, but they’re not showing up as such on anything but renders. Hell, I don’t even know why they were made. Any quick way of identifying and fixing them? Thanks

Probably a flipped normals problem.

In Edit mode, select all faces (A) then Recalculate Normals Outside (Ctrl+N).

Hope that helps!

Thanks for the help. The model now looks less screwy when viewed as “solid” or “textured”. However, the same faces are still showing up as black on renders. Any other ideas?

Post a render and a dump of the mesh, that will help people see the problem. :wink:

And try it with Unified Render on.

Tried it with unified rendering on, and got the same results. Forums don’t support attachments, and I don’t have an account on any image hosting site. But here’s the content of the .blend-(removed)

Hmm, looks like it gets cut off. Damn.

Oh, forgot to mention. I tried looking at the other side of the face, but it wasn’t front-facing either (also black).

Not feeling quite as lazy as I was yesterday.
http://i42.photobucket.com/albums/e333/Baiame/helmet.jpg

The black face is clearly visible at the bottom, surrounded by several half-black ones. I also forgot to mention that I tried deleting the face and making it again- this didn’t work either.

From the render you posted, it looks like a problem I’ve had myself & discussed in an earlier forum:

With a Subsurfed mesh, the area on an object where light transitioned to shadow showed large black squares/triagles. It seemed that while the mesh was rendered smooth, the transition area revealed the geometry of the lower-poly version of the mesh (which is made up of larger square/triange faces, with solid shading).

If you are using the Subsurf modifier, make a duplicate of the model and move the original to another layer (to retain an editable version). ‘Apply’ the Subsurf modifier to your copy and render to see if the artifacts remain.

If this doesn’t solve the problem, check for duplicate faces or verts (maybe try this first if you haven’t already). Select all in Edit mode & Remove Doubles.

I have only a vague idea of what a “subsurface” is, and any use of them I made was entirely unintentional or consequential. I tried applying the subsurf modifier, but the problem remained (and it seems there’s no duplicate vertices or faces, either). Any other ideas?

No other thoughts off hand. Send the .blend to [email protected] and I’ll take a look and see if I can help.

I checked the .blend you sent, and narrowed down (somewhat) the problem. The artifacts only appear on certain faces (why???) when lamps with raytraced shadows are used.

Turning off the the RayShadows of the lamps gets rid of them, but of course you may still need those raytraced shadows!

There is an easy solution: a button . . . in the Shaders tab of the Materials Panel, click the Bias button (tooltip gives an explanation that fit my theory).

Glad I found this . . . helps us and hopefully others who have been asking about similar problems.

Thanks for all your help. By the way (and I should’ve mentioned this before), this is part of a model to be used in a game. So if this is just a rendering problem within Blender, I wouldn’t suppose I have anything to worry about.