What is topology?
The arrangement of geometry of a model, the flow of edges around and throughout the 3D form.
What is retopology?
Creating (good) topology after the model – with all its parts and detail – has been created.
Basic sculpting-retopo workflow (using Sculptris, Max, and Xnormal):
1. Sculptris – sculpt your model, not worrying about poly count, or good topology. Just concentrate on good proportions, anatomy, design, and attention to detail.
2. Sculptris – export hi-res model as an obj
3. Max – import hi-res
4. Max – retopo, creating a new model (much lower poly, with good flow) that conforms/sits right on top of the existing, hi-res geometry
5. (optional) Max – delete hi-res from scene, keeping new lo-res retopo-ed model
6. Max – lay out UVs for lo-res
7. Max – export lo-res from as an obj
8. Xnormal – import both lo-res and hi-res models, generate normal map by baking hi-res detail onto the UVs of the lo-res
Workflow tips for retopoing a Sculptris model in Max
1. Export obj (“hires”) from Sculptris
2. Import into Max, in import dialog everything should be UNCHECKED except: Import as Single Mesh, Flip ZY axis, Normals-From SM group
3. Shaded (not Realistic) in viewport
4. Right click Shaded in viewport, Viewport configuration, check “display selected with edged faces”
5. Rename object to hires, convert hires to editable poly
6. In ribbon, select Freeform tab
7. Draw on (“Grid”), select Draw on: surface, pick, click on hires
8. Click on Polydraw to expand, click “New Object”, rename lores
9. Open Schematic View to be able to select both objects
10. Right click hires, choose Object Properties, select Freeze, see-through, hit OK
11. Select lores (use schematic view if needed), add a symmetry modifier (X axis), select editable poly, click on Show end result on/off toggle under modifier stack so you can continue to see the symmetry
12. Begin creating new topology (polys) on top of the hires by clicking on Step Build (freeform tab of ribbon) – click to create four points, shift-left click in the middle to create
Great retopo tutorial video: http://www.youtube.com/watch?v=-o8NgLJ1MJ0