# simple questions from newbie....

Question 1)

What are “coincident” vertices? I’ve checked the dictionary, but there’s no second definition beside the meaning of “happening simultaneously”…

Question 2)

What is the function of “recalculating normals”?

Question 3)

What is the function of a cursor that looks like an “aim” of gunshooting which is a ring of red and white color?

Question 4)

How is “median point” different to “3D cursor” in pivot point?

thanks for any help

verticies that are at the same place

the normals define which side of a face is the inside of the mesh, and which side is the outside.

in the game engine [and other programs] by default you can only see the outside of a face, so having the normals properly calculated is a must

usually blender will work okay, but not always. Also, you sometimes want the normals to point inside [control+shift+n] such as in a building.

new objects are added at thate position

it’s called the 3d cursor

also, it is possible to rotate and scale around it [hit the period key to switch to scaling and rotation around the 3d cursor]

yeah, I just described that… the median point is the center of what you have selected [hit comma to scale/rotate around it]

the 3d cursor can be anywhere you like

thx z3r0 d!!

however, I still dont get the function of “recalculating” normal…

For example, when I make one side of a ginger man, and duplicate that side and flip one of them 180 degrees, ie, a side which is a reflection of another, and then, I set smooth all of them… However, you can see a funny line in the middle… by pressing “recalculating normal” function, the line disapears.

How does “recalculating” normal alter that?

It is possible to determine which side of the mesh is outside/inside if it is manifold. Recalculate normals exploits this fact and turns all normals so that they point outside.

If you have a non-manifold mesh, meaning that it’s impossible to determine which side is outside and which side is inside, recalculating normals doesn’t work normally.
ctrl-shift-alt-m shows you the part of the mesh that are non-manifold. It is a very useful tool for finding mistakes in mesh.

You can see the normals drawn if you hit “Draw Normals” in Editing\Mesh Tools 1 while in Edit Mode.

The line in the middle is caused by ‘bad’ normals, or normals that are flipped the opposite way to the surrounding ones. Before you recalculated the normals, you would have noticed that when you select the object and press ‘F’, the normals in the center would have been pointing inwards. The recalculate normals option just flips all the normals outside.

I hope you understand what I am trying to explain…

From Daniel

What is “manifold”?

sorry for the ignorance…