3D Modelling for Computer Games - Normal Maps and Baking

In 3D modelling, every artist needs to consider Parameters, specifications and budget when modelling, as there can be multiple of each of these within any given brief.

Exaggeration is always used to display emphasis on reality, a model with very small sections of mesh, such as fine edges, lips or ledges will subsequently have very small resolutions in a texture, as such the model, whilst looking real to life, does not display as well as it otherwise could, due to the texture space being restricted.
This is why it is necessity to exaggerate the models features, giving more detail to otherwise flawed parts of a mesh, making the detail pop giving it more visual appeal.

Holes are to be avoided within a mesh and must be filled before baking, they can either be represented using an alpha map or can be filled. Holes can present a multitude of problems within baking. These are present for example in a gun muzzle brake or a heat guard on a gun barrel, provided the artist can produce a good quality alpha map the holes can be represented as such, but in most cases the holes will be painted black, unless the section of the gun is to be seen at specific angles on a frequent basis, alpha maps are not necessary.

It is always necessary to ‘kitbash’ a mesh, for this purpose any artist must produce their own library of kitbashing meshes, this can consist of screws, bolts, rivets, wires, panels and much, much more. Each kitbash piece of geometry can be parented to the main body geometry also for ease of selection, triggering everything to be selected upon selecting the main high poly mesh.

It should be habit when modelling to save the file regularly, especially when gearing up to perform a bake.

When baking a high poly mesh down to a low poly, it is necessary to be in the habit of three things. Saving frequently, using a different iteration name each time so to have a history you can return to if necessary. Returning the mesh to the centre of the world, freezing the transformations and deleting the history, this allows for the bake to be completed more accurately with as few issues as possible.

Render file type is down to your own workflow, and can be rendered as a Targa (TGA) for the sake of speed, however I prefer to bake as a PSD file, as this is native to PhotoShop and can be modified if necessary, this acts as a master document to export from following any subsequent changes

It should also be habit when baking to set both Maya Common Output and Mental Ray Output to an identical map size, if you set one to 1024, the other should be 1024, the same with 2048 or 4096 texture size.  

The UVs are pivotal to the bake of any model, due to seams created through the process of unwrapping.
Seams will occur in absolutely every model ever created, and there are multiple ways to hide seams from sight.

• Hide the seam with detail, for example adding a coat to a character to hide certain body seams, or adding certain features to a hard surface model.
• Using seam lines provided by material changes. Finding a spot within a mesh which can be used for seam creation is incredibly useful too, for example the containment chamber I am intending on producing has a steel panel at the rear for maintenance access, this will allow me to insert a seam where the steel begins and the other materials used for the chambers body end.
• By design, the seams can be placed by design, if for example a surface has a separation in the mesh by design, within the details, the edges can be split along this edge, and the seam can be hidden well.

When baking, there must be an adequate level of detail in the mesh to display the bake accordingly, as can be seen below, the bake does not take to the lower polygonal mesh as well as it does to the higher polygonal mesh next to it, with the indentations being represented clearer and and screws also being more pronounced and less skewed. This must be adhered to as well as possible, though it must stay within a poly budget for any given mesh.

Overlapping vertices are NOT allowed within high to low poly baking, as they will not produce a successful bake, the vertices displayed on ANY axis always need to be displayed at an angle, therefore any extrusions created must be scaled in slightly to any angle less than 90 degrees. This will allow the object to bake and the result will represent the extrusions in correct space

Any extrusions from a model are not surface details, as they are modifications to the silhouette itself, a normal map will bake in surface details and not change the silhouette of the model itself.

As can be seen below, the direct vertical extrusion on the left of the two models would not bake correctly if the bake were to be projected downward. The right of the two meshes would project the 3D result in a bake as the vertices are not overlapping at all.

I will be looking to bear all of these in mind through the development of both my high and low polygonal meshes, provided I can stick to these I should be able to produce a high quality model and normal map, ready for in-game use.