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3D Coat low poly Retopology
Entry posted by YouGroove
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A quick overview of 3D coat Retopology with some tips also.
The goal is to retopology previous high poly model from Sculptris into a Low poly model in 3D coat :
Fisrt step is import obj model in 3D coat as Reference model, we will use the model below from sculptris.
Begin in symmetry mode to add a polygon to start :
Then use 3D coat quads to very quicly add quads over the model :
You will need to have a good toplogy so follow lops and edges
The goal si very low poly enought so not lot of detailling
In early steps we will check if normal map rendering is ok.
So let's begin to make some UV seams loops and Click unwrap
On normal map generation parameters :
You can adjust the two values if needed or if you have map glitches
The second paramter choosen is : keep cage point weld to exterior surface
Choose low resolution to render and test fast
Than launch render normal map.
In paint view in sub objects panel : hidde default hight poly
Than check low poly retopo and normal map
Some tip on Preference window of 3D coat :
I choose alwats Maya as parameter for normal map calculation insteda of 3D coat ones and results are really good.
Continue Retopo following loops
Use loop cut when needed (specially where it will be bending animation possible)
From cylinder create more faces for a bigger cylinder jonction
I could use lines drawing , but quads are fast enought in some cases to make a cylinder
Begin legs area :
Add more polygons to make some round circel from where we will make the legs parts
Special method here some time faster for some stuff :
instead of drawing lines make a long cylinder
Than use Lopp cut
You will have to adjust vertex and sometimes delete / remake some quads
So better use draw lines, but this method can work also.
The vertex seems deep inside the model like below , because Zbias paramter is low like 3.0 not always good.
Change it to 10
The vertex will be outside of the model and you will be able to move them or do anything else now.
Main parts are done, you can make uv loops and test normal map generation to see if
some correction are needed.
Now for the arms we will use a standard and fast technique : Drawing lines
Click enter to generate the polygons
Once this is done, sometimes you will see lot of polygons that can be reduced manually to optimize your low poly model.
Just move vertex very near another to join them , or use "Fusion" tool on 3D coat.
For foots, its just polygon drawing
Beginning the hands
Making additionnal objects retopo
Once all is done make the loops semas UV and check model
picture below UV are not colored, a 3D coat big appeared in fact
Because of symmetry retopology and texture, you will use half texture mirrored in game.
But the with the normal map it will be lot more visible than a simple diffuse map
Like below :
Because of the UV semas beeing in the middle symmetry line :
This will be oubvious in game on your 3D engine if your camera will be not too far from character
To avoid that you'll have to use a different UV mapping to hide the UV seams :
Some another good example to avoid the middle visible line seam on character
So here is how to do that in 3D coat :
Uncheck Virtual mirror :
Apply symmetry retopo and UV to all layers :
So all Retopo and UV seams will be copied in other side.
Next step is remove all middle line UV seams , and make new UV seams loops on entire character as examples above.
Because you no more use Symmetry to optimise bitmap size, you can adjust similar UV islands to be in the same place in the bitmap, for example the arms or hands :
You'll have to mirror Uv semas : Flip U or Flip V in 3D coat , than rotate/move UV seams to be perfectly one over the other
You have some usefull tools in 3D coat :
-Auto UV for non 3D artists, not best results indeed but can be good in some cases
-Relax tool to use on UV when they are too shrinked on some zones
So the model is ready to bake normal map :
After normal map baking here is the low poly model with normal map ready to paint :
3D coat wireframe view :
(Next step perhaps model painting in 3D coat ? )
As you can see 3D coat retopo is very fast and easy and fun.
I hope you have enjoyed that retopology overview 
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