Now that the fun part is over i will take the low poly version i have done in the beginning and change it to conform better with the high rez version. I use topogun for this ... import the low version and one of the higher levels as a reference model and i will change the topology however i want and i will make sure that the low poly will resemble as best as i can with the high version in order to get good normal maps when baking normals.
I will repeat the same process for every piece i have sculpted separately and when all are over i will be ready to go to the next stage : baking the normal maps.
4.3 Transfer Maps:
At this point the low poly version and all the high rez pieces are ready and i will continue with the uv mapping.
There are a lot of tools for UVs that you can use :UVLayout, Unfold 3D, plugins for pelt mapping etc... and some say one is better than other but i do all my uvwork with the tools built within maya, they might require more attention and planning on where to cut the UVs and sometimes will produce junk UVs but after a second trial things work well. I have tried Headus UVlayout and Unfold also but i like better the maya unfold ... works faster for me .
I won't show you how i worked on uvs because lots of the people i know don't use maya for uvmapping and most likely the information i will give will be redundant.
The idea is to unfold the uvs with little stretching ,a good hint is to keep your cuts in the less visible parts of the model(like for the arms and legs keep them on the inner part) and you could break down the uvshells accordingly to the pieces in the high rez version ( for instance boot will go as one shell , each leg as one shell etc ... )
After the UVs are done i will be ready to bake normals and other maps if necessary.
I used transfer maps tool within maya for this ( but render to texture within 3dsmax works the same way ).
I will exemplify this process on the boot:
-before starting keep in mind that the uvs on the piece of geometry you are going to bake normals for should not overlap (in the end you can overlap uvs for arms or other similar objects but for accurate results move the overlapping uvs outside the 01 space or shrink them down in a corner or unused space while baking)
-import both low and high versions into maya and make sure they are on top of each other
-open the transfer maps dialog ( found in Rendering menus in Lighting/Shading-> Transfer maps... )
-select the low poly version and in the Target Meshes click on add selected , then select the high version and in the Source Meshes click add selected (see image above)
( if you do not add any geometry to the Source Meshes then maya will sample all the geo in the scene for the process )
-in the Display option for the target mesh select Envelope ( or you can select both to display both the target mesh and the envelope)
-this will create an user-editable geometry ( merely an offset of the current low poly version ) that will be used as an envelope to look for the source meshes. You can change the offset of the envelope by changing Search envelope% slider ( or by typing a value ); the idea is that you will get better results if you will have the high rez version inside the envelope (like in the third case in the next image)
-if you go too far with the offset the baking might not work properly , usually i will trial and error some values for the offset until i have most of the high rez inside the envelope like in the image below
and then select the envelope and tweak its vertices/faces/edges until the high rez will be completely inside the envelope
-then select the maps you will like to bake ;i will resume to normal map ( you could also bake ambient occlusion maps ... this way you will sample the ao from the high rez version but i did not have too much time to compute ao maps also because they require some time to render ... depending on your machine ... mine was too slow at that time for this ; instead i used Batch bake mental ray with the normal mapped low poly to bake a Final Gather pass for occlusion ... works a lot faster with comparable results... see later on for details) also make sure you browse for a path to save the file ,select file format,map dimensions and other details you want, also make sure you set the search method to inside envelope only since the high rez will be inside the envelope