Multi/Sub-Object Material

The trick to having multiple materials assigned to a single object is to use a multi/sub-object material. A multi/sub-object material is simply a container for other materials. As its name implies, it works at the sub-object level, assigning different sub-materials to different sub-objects of the model. (A variety of object types have sub-object levels, especially the surface models: editable mesh, editable poly, editable patch, and NURBS.)

Assigning sub-materials is a two-part process:

• Assign Face sub-objects a material ID value.
• Match materials contained in the multi/sub-object material to the ID values on the faces.

You can do these steps in either order.

Set up the scene:

You can use a prepared file, or the file you worked on before. Do one of the following:

• • Choose File > Open. Locate chairs_assigned.max in the \tutorials\designviz folder, and click Open.

    If you see the File Load: Units Mismatch dialog , choose the option Adopt The File's Unit Scale. This will change your system unit, so be sure to reset your system unit after completing this tutorial .

    To reset your system unit, go to the Customize menu and choose Units Setup > System Unit Setup > System Unit Scale > Inches.

    If the geometry is not visible in the viewport, click the Zoom Extents All button twice to correct the display.

  • Choose File > Open. Locate the file you created (chairs_with_materials.max), and click Open.

    The chairs have materials assigned, but Leather Parts and Wood Parts are still two separate mesh objects.

  

  Wireframe views show that the leather and wooden parts of the chairs are two separate meshes.

Plan and assign material ID's:

When you work with sub-object materials, the first thing to do is to plan how to map the material ID numbers. The values on the geometry must match the values in the material, and vice versa. This is not a task for the 3D software, but for a design document, even if it’s only a scrap of paper.

For this model, the wood parts will retain the default material ID of 1, and the leather parts will have a new material ID of 2.

1. Select the Leather Parts mesh.
2. Go to the Modify panel. The modifier stack display is the window below the object name and the drop-down Modifier List. This is where you choose a sub-object level. Click the plus icon next to the name Editable Mesh to see the mesh’s sub-object levels.

   

   

   Top: After clicking the plus icon, the stack shows sub-object levels.

   Bottom: The sub-object levels in the stack display.

3. Faces are the smallest renderable portions of a mesh. Click Face in the hierarchy.

   

   The stack with the Face sub-object level selected.

4. Choose Edit > Select All.

   This selects all the faces in the Leather Parts object. By default, sub-object selections display in red.

5. On the Modify panel, go to the Surface Properties rollout. (This is the last rollout on the Modify panel.) In the Material group, increase the Set ID value from 1 to 2.
6. In the modifier stack display, click Editable Mesh again to return to the top, object level.

Combine the two meshes:

1. In a viewport, select the Wood Parts mesh.

   The wood parts have material ID 1, so it makes sense to make them the basis of the combined mesh.

2. Go to the Modify panel. On the Edit Geometry rollout, click to turn on Attach. Then, in a viewport, click the Leather Parts mesh to attach it.

   An Attach Options dialog is displayed.

   

3. In the Attach Options dialog, choose Do Not Modify Mat IDs Or Material, then click OK.

   This option leaves the material IDs on faces unchanged.

   TipAfter attaching the parts of your model, be sure to turn off the Attach button. If you don't do this and want to make other object selections, you will inadvertently attach objects you don't want attached.
4. In the object name field at the top of the Modify panel, type Chair Group.

Create the multi/sub-object material:

1. On the toolbar, click Material Editor.
2. In the Material Editor, click the third, unused sample slot to make it active.
3. To the right of the material name field is the Material Type button. At present, its label says “Standard.” Click this button.

   The Material/Map Browser is displayed.

4. In the Material/Map Browser list, double-click Multi/Sub-Object.

   A Replace Material dialog is displayed.

5. Choose Discard Old Material, then click OK.

   The Multi/Sub-Object Basic Parameters rollout is displayed in the Material Editor.

   

6. By default, the multi/sub-object material contains 10 sub-materials. The chair group model needs only two. On the rollout, click Set Number. In the Set Number Of Materials dialog that is displayed, reduce the Number Of Materials value to 2, then click OK.
7. Drag the sample slot that contains the Black Leather material to the Multi/Sub-Object Basic Parameters rollout, and release the mouse when you are over the button for the second sub-material. This button is in the column labeled Sub-Material.
8. In the Instance (Copy) Material dialog that is displayed, leave Instance chosen, and click OK.

   The new sub-material corresponds to Material ID 2.

   

   Controls in the Multi/Sub-Object Basic Parameters rollout after dragging the Black Leather material to the second sub-material’s button.

9. Drag the sample slot that contains the Wood 1 material to the Multi/Sub-Object Basic Parameters rollout, and release the mouse when you are over the button for the first sub-material. As before, accept Instance and click OK.

   This sub-material corresponds to Material ID 1.

   TipYou can change material ID assignments in the Material Editor, by editing the values in the ID column of the Multi/Sub-Object Basic Parameters rollout. You can also change them on the geometry side by using the Material group of the Surface Properties rollout.

   

   Sample sphere for the multi/sub-object material

Assign the material to the mesh:

The multi/sub-object material is now complete. The last step is to assign it to the model.

1. In a viewport, click to select the Chair Group model.
2. In the Material Editor, click Assign Material To Selection.

   The appearance of the model is unchanged, but it now consists of a single editable mesh, so you can use it with the Substitute modifier.

   

Save your work:

• Save the scene as chair_group_single_mesh.max.

Next

Creating 3D Materials: Another Approach to Wood