3D Crash Course
Note: I was building this blog post while watching Harry Potter and the Sorcerer's Stone. If at any time the writing starts sounding more like spells than coherent sentences I apologize in advance.
Since I went to school for 3D like most I assume a lot of this is common knowledge. It is actually really hard to know exactly where to start when a colleague asks what they should know about 3D to get into VR. I guess it is best to not talk in terms of Maya this or Max this and just define the commonalities of workflow, geometry, performance, general good practice when it comes to 3D.
When you reduce all the crazy character models(+200k polys for film at times) down to the most simple part it is a single polygon. a flat little plane. It always has the same features as I note above. Inside of 3D modeling software a user is able to use any of these as handles for manipulation. You could move a single vertex or a cluster. Same as edges and faces.
Here is the same breakdown with a complete piece of geometry. This cube is above is triangular(three sides). Triangulation is most common in gaming models. The cube below is made of quads(four sides). In any case models should not have ngons. Ngons are polygons with more than 4 edges. E. Vertex F. Edge G. Face H. Border Edge. Important to note, UVs(for texturing) are most typically paired with a vertex.
I. This is an example of proper more complex quad geometry. Sometimes quads can look funny but in 99% of the cases it is better to have a goofy quad over a ngon or a tri(if your geometry is all quad).
J. This geometry is an example of two cubes intersecting. If you are deleting faces this is fine for lets say a chair. But, if it were a hand or something that will be dynamically animated it will not work well. Best to avoid.
K. This is an example of non-manifold geometry the edge. Do not do this!
L. Another example of non-manifold geometry two polygons only linked by a vertex.
M. Basic Geometry
N. Geometry unfolded by its UVs. This is usually in a particular fashion for efficiency sake. Avoid distortion in the layout.
O. UVs are laid out and sent over to photoshop for a bit of a paint job. There is a diffused texture layer. That would be basic colors etc. There is also a multitude of different texture layers most consisting of a greyscale 0-100%.
P. Here is what this geometry would look like after the texture has been applied.
Here is an example of a model that has a "rig" it is basically a skeleton that the animator will use to animate. The rig itself usually has handles as you see around the models head. IK stands for inverse kinematics. The short of IK is as an animator you can move the hand and the arm chain follows it around which is quicker and tends to look more natural. FK stands for Forward Kinematics for animators this will usually take more time to key and animate. If I wanted to have a character point I would need to rotate shoulder and set key. Then, I would need to rotate elbow and set key. Then, I would need to rotate wrist and set key. Downward to the fingers. There are times when you have to switch from the IK chaining. Typically, there will be a switch for that. On the far right are head shapes that are called "blend shapes" these are bound to the main head and referenced by the main head when they are both connected to the facial control(middle). So, in a lot of ways although you can get unique looks from the character the extreme facial expression positions are very much established well before animation happens.
Lots of different 3D files. OBJs and FBXs are fairly universal. They work fine in Unity. I should note you can retain animations in an FBX vs. a OBJ. MA and MB can be used in Unity as well. The nice thing about MA and MB for Unity is you can quickly iterate.