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Introduction to Parametric Modifiers in GMAX

Started by joelyboy911, March 03, 2010, 02:14:50 AM

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This tutorial will deal with a little tool in Gmax called the Parametric Modifiers. You may have seen them there in the Modifiers Roll-out and wondered what the heck they were for. This tutorial should help you learn to use them, but to get used to using them and figure out all the things they can do, you'll need to experiment and play around with them yourself.

Before reading this tutorial you should already know how to move, resize and rotate shapes, as well as use the "Edit Mesh" function.

Getting Started

To demonstrate the different modifiers in this tutorial, I'll be using basic geometry such as cubes and planes, but there is one very important pre-requisite to the objects you use Parametric modifiers on: They need a lot of vertices. To do this, change the number of "segs" (segments) for width, height and length. As you get to know the modifiers you can get used to knowing how many of each you need to get the desired effect. If you use too few, the surfaces you modify won't appear smooth. These modifiers only move the existing vertices, they can't make any more.

When you have the object you're going to modify, click the blue rainbow and open the Modifier List and scroll down to Parametric Modifiers. Here you will find roughly 15 different terms. This Tutorial will explore 11 of them.

When you choose one of the options, a new input dialogue-type thing will appear under the Modifiers roll-out. Manipulating these controls is what will make you good at Parametric Modifying.


To put a simple bend in your object, simply choose the axis you want, and add or subtract from the "angle".

For more complex bends, you can change the value of "direction" or use the Upper and Lower Limit values. You can also click the little + next to "Bend" in the Modifiers Stack

Then you can use the "Gizmo" or the "Centre" to move the effect of the bend in relation to the object. As with all Gizmos, you move it using the Move tool, just as you would move any object in Gmax.

The Bend modifier is among the most useful of the Parametric Modifiers. You can use it to make curved roofs, for example, or to bend plumbing, as Driftmaster asked me how to do.


The taper tool is also a useful one. It is used to make the object more pyramid-shaped (it squashes/englarges one side of the object). This happens when only the "Amount" figure is changed in the command panel.

When the "Curve" figure is changed, it gets more exciting.

If you use "Curve" but no "Amount" you get either a bulge out or a suck in on the axis of the shape selected in "Effect"

When you use both figures, you can make useful/interesting shapes.

Maybe this could become the top of a post-modern minaret?

This could be the Capital of a Pillar?


This modifier's name is pretty self-explanatory. It has one main input figure - "Angle".

That figure is the number of degrees the shape will be twisted. Limit can also be used, and Bias has an effect as well. I advise you to experiment with these if you want to know more. (I can't spoon-feed you all the info :P)


This is one of the (on the whole) less useful features.

By selecting "Fractal" and adding to the "Strength" on the axes you want to add noise, you can add a degree of roughness to the object.


The push function appears (to me) to act like inflating the shape. By adding a positive number to the "Push Value" you get something like this:

I beleive it means that the corners (not to confuse with vertices) and edges are all pushed out from the centre.

However, if you put a negative number as the "Push Value" you may get something like this:

Interesting, no doubt, but not overly useful. :P


The Relax function is used to soften the edges of shapes - it can make a square box almost right into a sphere (but not quite).

By adding to "Relax Value" and then to "Iterations" you can achieve a progressively more exaggerated result.


The ripple effect adds ripples to the object. For that reason, I'll demonstrate on a plane.

The Amplitude figures should be kept equal if you want to have a pebble-in-the-millpond style ripple. If they are different, you will have a different effect (you should experiment with it if it interests you).

The wavelength determines how many ripples will appear on the object - the lower the wavelength, the more ripples in the space.


Wave works in a similar way to Ripple, but instead of creating a circular pattern, it makes a linear one:

There are still two amplitudes, and Wave Length. If you use Decay, the waves will lose amplitude (decay) with each phase of the wave. If you use the Phase command, the wave moves along its phase in relation to the object. Once again, I urge you to experiment with each and every one of the functions that you use.


Skew is quite simple. Its the same as skewing an image in MS Paint. You choose the amount, direction and Axis, and it skews the object accordingly.

Affect Region

Affect region is one of the harder modifiers to get right, as it can be somewhat complicated.

You change the effect that "Affect Region" has by moving the "Points"

Moving these is the same as moving the "Gizmo" and "Center" in the earlier examples.

If you change the "Falloff" then the Region that is being Affected changes size, and you can get something like this:

Once again, I haven't provided all the details, give it a go yourself and play until you get it right.


This modifier is a very interesting one. It works by adding a bitmap to the object to raise vertices, like transferring a relief map into 3D.

I made this grayscale bitmap:

Then, I clicked on "Bitmap" and navigated to the bitmap I created.

By adding "Strength", you can control the height of the mapping you've done. As you can see, I've ended up with a perfect model of a err... volcano. This function can be used to make a gmax model of your region if you have the grayscale of your map available. Otherwise it can be used to add detail to objects without moving individual vertices.

I can't stress enough the importance of experimentation. If you try and don't succeed, try again.

There are some of the Parametric Modifiers not included in this tutorial. They are Slice, Xform and Preserve, because I don't know what they do, and Mirror because that one is very self-explanatory.

Best of luck using Parametric Modifiers to improve your BATs!
SimCity Aviation Group
I miss you, Adrian


My BATs or here but it is in french ;)



that's a really handy guide Joel, :thumbsup: :thumbsup:

I've figured most of this stuff out now,but this would have made the process a lot less painful, and I'm sure it will help others.


I'm a little confused about a step. Right after the box is changed to a arch you have it turned into a arching tube. To ensure that I understand the tools functions can you explain how this was done. I have tried to reproduce without success. Thank you for this tutorial btw.