6 min read

(For more resources related to this topic, see here.)

High poly model import

Different applications are biased to different file formats and may therefore have different import procedures. The Send To functionality between 3ds Mudbox and 3ds Max(which is possible as both are Autodesk products).This is essentially a .fbx transfer. If you are using ZBrush, you will want to get used to the GoZequivalent transfer feature. Note that GoZ must be run from ZBrush to 3ds Max before it can go in the other direction. GoZ also works the free, mini-modeler tool from Pixologic(who make ZBrush too)called Sculptris, which is available at http://www.pixologic.com/sculptris/. In the following example, we’ll directly export from Sculptris, a model made from a sphere(so it needs retopology to get a clean base mesh). We’ll export it as a .obj and import it to 3ds Max in order to show a few of the idiosyncrasies of this situation. With a model that is sculpted from a primitive base, such as a sphere or box, there are no meaningful texture coordinates, so it would be impossible to paint the model. Although many sculpting programs, including Sculptris, do automapping, the results are seldom optimal.

Importing a model into Sculptris

The following steps detail the instructions on importing a model into Sculptris:

  1. Install Sculptris 6 Alpha and run it. Note that the default scene is a sphere made of triangle faces that dynamically subdivide where you paint. Use the brush tools to experiment with this a while.
  2. Click on Open and browse the provided content for this article, and open Packt3dsMaxChapter 9Creature.sc1. The file format .sc1 is native to Sculptris.
  3. To get this model to work in 3ds Max, you will need to choose Export and save it instead as Sculptris.obj.

Importing the Sculptris.OBJ mesh in 3ds Max

After we have imported a model into Sculptris, we’ll move on to see how we can save this file into 3ds Max. The importing part is fairly easy.

  1. In 3ds Max, choose File | Import and browse to Sculptris.obj, the mesh you just exported from Sculptris. You could also try the example .obj called Packt3dsMaxChapter 9RetopoBullStart.obj. The import options you set matter a lot. You will need to make sure that the options Import as single mesh and Import as Editable Poly are on. This makes sure that the symmetrical object employed in the Sculptris scene (actually a separate mesh that conforms to the model) doesn’t prevent the import.

  2. While importing, you should also swap the Normals radio button from the From SM group to Auto Smooth, to avoid the triangulated mesh looking faceted. A model begun in Sculptris won’t contain any smoothing information when sent to 3ds Max and will come in faceted if you don’t choose Auto Smooth. After importing, another way to do the same thing is to apply a Smooth modifier. The Auto Smooth value should be 90 or so, to reduce the likelihood of any sharp creases.
  3. Finally, once the model is imported into the 3ds Max scene, move it in the Z plane so it is standing on the ground plane, and make sure its pivot is at 0,0,0. This can be done by choosing Edit | Transform Toolbox and clicking on Origin in the Pivot section. Note that the model’s edges are all tiny triangles. This is a result of the way Sculptris adds detail to a model. Retopology will help us get a quad-based model to continue working from. The idea of retopology is to build up a new, nicely constructed model on top of the high-resolution model. The high-resolution model serves as a guide surface.
  4. If you are curious, apply an Unwrap UVW modifier to the model and see how its UV mapping looks. Probably a bit scary. A high-resolution model such as this one (250K polys) is virtually impossible to manually UV map,at least not quickly. So we need to simplify the model.
  5. If you can’t see the Ribbon, go to Customize | Show UI | Show Ribbon, or press the icon in the main toolbar.
  6. Then click on the Freeform tab.
  7. With the creature mesh selected, click on Grid in the Freeform tab. This specifies the source to which we’ll conform the new mesh that we’re going to generate next. We don’t want to conform to the grid, so change this to Draw On: Surface and then assign the source mesh using the Pick button below the Surface button, shown in the following screenshot:

  8. Each time you relaunch 3ds Max to keep working on the retopology, you’ll have to reassign the high-resolution mesh as the source surface in the same way.
  9. You could also use Draw On: Selection, which would be handy if the source was, in fact, a bunch of different meshes.
  10. There is an Offset value you can adjust so that the mesh you’ll generate next will sit slightly above the source mesh that can help reduce frustration from the lower-resolution mesh, which is likely to sink in places within the more curvy, high-resolution mesh. If you’re just starting out, try leaving the setting alone and see how it turns out. An additional way to help see what you are doing is to apply a semitransparent material or low Visibility value to the high-resolution model (or press Alt + X while it is selected).
  11. Next, in a nested part of the Ribbon, we have to set a new object or model to work on (that doesn’t exist yet). Click on the PolyDraw rollout at the bottom of the Freeform tab.

  12. Having expanded PolyDraw, click on the New Object button and we’re ready to start retopologizing. I would strongly suggest raising the Min Distance value in the PolyDraw section, so when you create the first polygons they aren’t too small. When using the Strips brush, usually I set the Min Distance to around 25-35, but it depends on the model scale and the level of detail you want. Just like with modeling, when you retopologize, it is best to move from large forms to small details.

    The object will be called something like Box001, an Editable Poly beginning in the Vertex mode. You can rename it to Retopo or something more memorable.

  13. Turn on the Strips mode and make sure Edged Faces is toggled on (F4) so you can see the high-resolution model’s center line. Starting at the head, draw a strip of polygons along the symmetry line so that there’s an edge on either side. As this model is symmetrical, we only have to work on half of it.

    If you hold the mouse over the Strips mode icon , you’ll get a tool tip that explains how Strips are made, and if you press Y, you can watch a video demo albeit drawing on the Grid. Note that the size of the polygons, as you draw, is determined by the Min Distance value under PolyDraw. Bear in mind that apart from the Min Distance value, the size of the polygons drawn also depends on the current viewport zoom. This is handy because when working on tighter detail, you’ll tend to zoom in closer to the source mesh.

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