Modifier Stack Standards

3D Modeler and Core Fundamentals

01. Getting Started

The Modifier Stack is one of the most powerful features of 3DS Max – however if not used properly it can make models very difficult to work with – especially in a high volume pipeline.

We have developed a set of rules and best practices to make sure that your models will work efficiently within a pipeline. Read through this document thoroughly to understand the requirements.

02. The Big Rules

a. Editable Poly at the bottom of the stack.
You should always have an Editable Polygon at the bottom of the modifier stack. This is because modifying a primitive (Box, Sphere, etc.) at the bottom of the stack can break all the other modifiers above it. Any other sort of “Editable” (Mesh, NURBS, etc.) is not allowed, due to most 3DS Max tools only working with Editable Poly.

b. Subdivision modifiers should not be collapsed.
These modifiers should not be collapsed. Subdivision modifiers include: HSDS, MeshSmooth, OpenSubdiv, Quadify Mesh, Subdivide, Tessellate, TurboSmooth. Generally we recommend using OpenSubdiv. We do not want collapsed subdivision modifiers because these can make the model very difficult to edit due to the high polycount.

c. Use the Symmetry modifier whenever possible.
The Symmetry modifier is very powerful and will mirror you mesh in a non-destructive way. However if you must use the Mirror Tool, use it only in Geometry mode. Transform mode will invert your mesh’s normals.

d. Unwrap UVW can be used above a subdivision modifier, but only to relax the UVs.
Placing an Unwrap modifier above a subdivision modifier will slow down the Unwrap modifier almost to the point of being unusable. In addition if you unwrap a mesh above a subd modifier and then change the subdivision level, you will lose all unwrap data.

e. Make fur with only with the VRayFur object.
Hair and Fur (WSM) modifier should be rarely used, and should never be collapsed into mesh. The only time we have seen Hair and Fur as an acceptable alternative was when rug fibers were shaped like large square strips of fabric. Otherwise VRayFur works every time.

f. For displacement use the VRayDisplacementMod modifier.
The VRayDisplacementMod modifier allows for much more detailed control over the displacement of a mesh, compared to what you will get from simply plugging displacement into a material node. For more information on how to use VRayDisplacementMod, see this tutorial.

03. Editable Poly Rules & Tips

Remember that we don’t want any other modifiers at the bottom of the stack:

INCORRECT

CORRECT

We generally discourage having a primitive at the bottom of the stack. You can add an “Edit Poly” modifier mid-stack to convert any object to an Editable Poly by using “Collapse To”.

05. Mirroring Geometry

a. Symmetry modifier
This is the best method for mirroring geometry. It is a modifier available in the modifier list and will (optionally) slice the model along the mirror axis and weld the two halves together. The mirror axis can also be transformed.

b. Mirror Tool
This tool is found at the top of the 3DS Max window and will open a separate dialogue box. It has more options than the Mirror modifier but it also creates a Mirror modifier in the stack. In this tool you can also use “Copy” or “Reference” to create a clone or an instance of the model, respectively.

When using this tool, you should always use “Geometry” – not “Transform”. This is because Transform mode will apply a negative 100% scale on your model, flipping it inside out. When you collapse the modifier stack, this will flip all the normals of the mesh and cause issues.

c. Mirror Modifier
We do not recommend using this modifier on its own. Even though using the Mirror Tool will create a Mirror modifier, creating a Mirror modifier from the drop-down list in the Modifier stack has less options than the MIrror Tool.

04. Subdivision Modifiers

Subdivision modifiers include TurboSmooth, Meshsmooth, and OpenSubdiv – though we only recommend using Turbosmooth and OpenSubdiv, and prefer that you use OpenSubdiv exclusively.

a. Why not collapse them?
In this example, the modifier stack is set up properly:

When a modification is required, such as lengthening the sphere into an oblong shape, it’s easy to just select a single face and move it:

However, if the subdivision modifier is collapsed then it becomes very difficult to perform that same operation. The modifier stack below is incorrect:

b. Why do we not put modifiers above subdivision?
Modifiers above subdivision can play havoc when the subdivision count is changed. Many 3DS Max modifiers rely on the amount of vertices from one modifier to another to be unchanged – and of course changing the subdivision count of a model will change the amount of vertices in it.

Below, an Edit Poly modifier was added above a TurboSmooth. The vertices were selected and moved:

But when the Turbosmooth iteration is changed from 3 to 4, the vertice count changes and the edits above the Turbosmooth break in the Edit Poly:

c. Exceptions to this rule:
There are a few exceptions to this rule – modifiers that do not rely on vert counts can be placed above a subdivision modifier.

i. Cap Holes
ii. Chamfer
iii. Clone
iv. Cloth
v. Map Scaler
vi. mCloth
vii. Noise
viii. PatchDeform
ix. SurfDeform
x. Unwrap UVW (only to Relax UVs!)
xi. VRayDisplacementMod
xii. VRayHairFarmMod
xiii. World space modifiers (WSM)

06. Unwrap UVW, UVW Map, UVW Xform

a. Creating and Editing
Any time you create and/or edit UVs, they should be done below a subdivision modifier:

The one exception to this is when you need to relax the UVs after a subdivision modifier. Applying subdivision can stretch UVs, so the one time you can put a UV above a subdivision is when you are using it only to relax the UVs.

b. After Editing
After you are done editing the UVs, we ask that you collapse the UVs into an Edit Poly. This will “bake” the UV data into the Edit Poly, ensuring that it does not get damaged or changed. Adding an Unwrap UVW modifier above the Edit Poly will allow you to edit the UVs that are baked into the Edit Poly modifier.