Model Rendering Oddly!

So I’m relatively new to Blender, I’ve started many models but never completed any, because Blender always inexplicably messes something up. I tried making a simple model tonight, and again Blender caused a problem that I can’t solve because I have no idea what’s causing it.

When my model is rendered with hard shading (top) nothing looks wrong. But when I try the same exact thing but with soft shading (bottom), it takes a scoop out of the side of my model for no obvious reason. Anyone know why??

do you only have smooth shading turned on?

Difficult to tell from screenshots. If you can post a .blend file (e.g. on others can d/l and check what’s going on.

My guess is that you’ve got some doubled up vertices messing with the normals/shading. In edit mode select all (A-key) search (spacebar) for remove doubles, and enter. This is also available in the Tools panel>mesh tools.

recalc normals

Which means go into edit mode (TAB) select all (A) and calculate normals outside (CTRL-N). Don’t worry about having to do this occasionally. I get messed up normals all the time, and I’ve been doing this for years. Nearly all the time a good old CTRL-N will clear it right up.

If that doesn’t fix it, you probably have some non-manifold edges. To find them, go to edit mode (TAB), de-select all (A), Go into edge-select mode (CTRL-TAB, 2) and hit (CTRL-SHIFT-ALT-M) and blender will select all edges that have a number of faces connected other than 2. That should give you a good idea where to find the oddness. This can be from generating multiple faces on top of eachother, holes in the mesh, or faces that are bridging edges that you didn’t intend, usually inside the mesh so you don’t notice. This happens to me occasionally as well, though most often when working with a lot of dense geometry, adding noise, and then removing doubles.

If you’re feeling daring, simply delete all the edges selected this way, which should leave you with a few holes in your mesh. To clear up the holes, select non-manifold again (CTRL-SHIFT-ALT-M) fill (F) triangulate (CTRL-T) and convert tris to quads (ALT-J). Works like a charm.

Good luck with learning Blender! Don’t get too discouraged. I know there’s like a million buttons and stuff, but you’ll get your bearings eventually.