Discovering Blender Sculpt: The Final Installment

Multires Sculpt

So you have put all your time and effort into sculpting your character or object and finally its finished and your very happy with the result. Now you may want to have your newly sculpted model in a game  or animation but as I have mentioned in the previous installments, a blender multires sculpt takes up so much of your system resources it would not be practical to use it in your project.

This is where render baking comes into play, think of it as a cheat… by using normal maps and displacements maps we can fake the a appearance of Blender sculpt model.

Displacement maps: will affect the topology of the mesh, some 3d Artists love using them and some don’t. I wouldn’t use them on character’s at all because they might end up giving you problems, if there going to be any deformations of the mesh, as you would see in an animated character. I would use them however if the object that the displacement map is going to be applied too is primitive, a plane or a sphere. For example a simple plane can transform into a mountainous landscape  or a simple sphere transforms into a craterous asteroid. Displacment map

Normal maps: do not affect the topology (they do not displace the objects/models surface), but it can fake the appearance of displacement. Normal maps are  usually related to gaming but are also used in animations and cinematic’s due to the increase in render times. Because it fakes the appearance of displacement there are some limitations to be aware of.Normal map

  • They’re great when viewed at a distance but not up close.
  • They’re best viewed head on and their limitation become apparent when viewed at extreme angles.
  • They should only be used to add medium to small amounts of detail to a model. For large detailing either model it yourself or add a displacement map

Bump maps: not an option when render baking but still worth the mention. Should only be used for the finest detail like fine wrinkles on skin.

The Second Model

Before we start baking we need two models in our 3D view, one is our blender sculpt model it has all the geometry and detail, the other will be the model used to bake the maps too, it is also the model we will use in our game or animation depending on the project your working on. This model should look almost identical(except for the detail), be the same size and occupy the same space as our sculpt model, it will also need to be UV unwrapped.

Retopo toolThere are a few ways of creating this second model either you can duplicate the multires/blender sculpt model and then “apply” the multires to one of them on a low level(I would suggest level 2 for animation purposes). You could use the Retopo (Redo topology) tool to create a new model using the blender sculpt model as a template(ideal for creating game characters). Or you could use a combination of both method’s to make the duplicated model animation ready.

Render baking simple as Pie

For render baking to work both your models have to occupy the same space in the 3D view. Put it simply one has to overlap the other, so to stop your self from getting confused I suggest putting the blender sculpt model in layer one of the 3d View and the other in layer two, and activate both layers when you need to. I will mention again to make sure that the second model is unwrapped with a saved image texture in the UV window. UV unwrapped modelThis image texture is important because any map(normal/displacement/AO) you wish to bake will be baked to this image.

  • Now it fairly simple from here(make sure both models are visible in the 3D view), select the blender sculpt model first then select the second model.
  • Press F10 in the buttons window and look for the bake Tab.bakeoptions
  • There are  few buttons and a big one that says Bake but before we click on that we have to press the “Selected to Active” button(it means the last object selected will be the one that will receive the baking).
  • Now look at the list of options on the right.  I want create a normal map so I click on the “Normals” option.
  • Notice a drop down menu has appeared, listing different ways of mapping, for character models it best to use Tangent.
  • You can play around with the other settings but I find the default values work just fine.
  • Now lets press that big Bake button, If you have the UV window open you’ll notice that the image texture is being overwritten by the Normal map.
  • Once it has finished select Image menu in the UV window and click on “save as” to save your file.

Thats pretty much it, all you need to do now is apply that normal map to the model and render it out.

Multires Sculpt model Compared to a Subsurf model with a normal map

Faking the look

There is some thing that  you may notice after applying your normal map and rendering it out, comparing it to a rendering of the raw blender sculpt model there will be a slight loss in quality. This to be expected though as you are no longer relying on those millions of polygons to give you the detail, but consider this… would you rather have a render that takes 2 hours or a render that takes two minutes? You might not notice the difference between the two renderings  until ambient occlusion(AO) is applied to the scene.  On the blender sculpt model there are plenty of cracks, bumps and crevices that AO can take hold but on our second model the surface can be completely smooth.

You can get around this though, by baking an AO map, as you would the Normal map, then adjusting that map in in you favorite image editor by increasing the contrast then importing it back into blender via the texture channel and in the “Map to” panel located in the Material settings set the “col” to multiply.

AO adjusting contrast

The reason why I have adjusted the contrast is that If I kept the gray colour it would effect the colour of the material/shader.

Another thing worth mentioning with regards to baking Displacement maps, there is no point baking a displacement map from a level 7 multires model (a normal map should be used at this level), displacement maps should only be made from the lower levels like level 2 or 3. If you have a model at level 7 but want to bake a displacment map at level 3 set the render setting in the multires panel to 3.

Well this is the end of Discovering Blender Sculpt and I hope these articles have been of some help.

<–Discovering Blender Sculpt: The Third Installment

Content Copyright© 2009 Lindsay C. Kerr


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