A Fine Hat
In No Time Flat

A Tutorial for Surface Tools

Tutorial by Jacques Hennequet
Supplement to his 3DA#31 page 26 report on "Surface Tools"

The author's magazine article tells about patch modeling in general, and in particular reports on Digimation Surface Tools (created by Peter Watje).
___ An important point about Surface Tools is that Peter Watje has now created a number of free plug-ins that aid in working with his commercial product. These can be found cross-indexed under "Surface Tools" in the Plug-Ins Keyword Index on The Max2 Page.--Ed.

As an example of what I talk about in my 3DA#31 report, we will build a hat using Surface Tools in Kinetix 3D Studio Max r2. I chose this object for two reasons:

While apparently simple, a hat is not easy to model as a mesh. The initial revolve of a spline requires fairly lengthy modifications to bring it close to a convincing hat.
3DS Max r2 has a hat tutorial illustrating NURBS. I thought it would be interesting for users to see that a similar hat can be built using patches.

Step 1: Creating the crossections

In the top viewport, create a five-sided Ngon with a radius of roughly 100 units. Make sure that the Circular option is checked. In the Modify panel, apply an Edit Spline modifier to the Ngon. Go into Sub-Object mode and select Spline.
___ Switch to the front viewport. On the toolbar, choose Select and Move, and restrict movement to the Y-axis.
___ Shift-select the Ngon spline and move the copy down about 20 units. Shift-select again, creating another copy of this spline, and move it up about 80 units. Leave Sub-Object mode and deselect the spline.
___ Switch to the top viewport and create a circle 80 units in radius. Switch to the front viewport and move the circle up about 40 units.
___ Select the Ngon spline, choose Attach, and select the circle (all crossections must be part of the same spline).
___ Go into Sub-Object mode, choose Spline, select all the splines. Choose Non-Uniform Scaling in the Toolbar, restrict to X-axis, and scale the splines to 80% of their original size.
___ Now select the bottom and the top three splines only. The second spline from the bottom in the front viewport should not be selected (it will become the hat's brim). Choose Select and Uniform Scale in the toolbar, and scale the selection to 80% of its original size.
___ Finally, select the circle spline (the second one from the top, in the front viewport), choose Select and Non-Uniform Scale in the toolbar, restrict the scaling to the X-axis, and scale only that spline to 15% of its size.
___ Your viewports should look like in Figure 1.

Figure 1 (click to see full size)

Step 2: Applying the modifiers

In the Modify panel, apply the following modifiers to the object: First a Surface Tools Crossection modifier, then an Edit Spline modifier, and then a Surface Tools Surface modifier. This order is important. The Edit Spline modifier allows you to manipulate the control vertices later. However, due to an apparent bug, it cannot be applied after the Surface Modifier. (If you forget, just remove the Surface modifier, apply an Edit Spline modifier, and then reapply the Surface modifier.)
___ Go to the Display panel and uncheck Backface Cull.
___ Your display should look like in Figure 2.

Figure 2 (click to see full size)

___ What you have is something vaguely reminiscent of a hat, but I doubt that anyone would want to wear it. We'll fix that in a moment.
___ Notice that Surface Tools properly curved the surface down from the brim, then back up to the top of the hat, and finally back down into the crease (although the crease needs work).

Step 3: Modifying the hat

Surface Tools has generated a patch object that we can now easily modify.
___ Modifications can be applied at two levels:

Going back to the Edit Spline modifier just before the Surface modifier, select Sub-Object and then Vertex (if not the default choice). Lower the Weld Threshold value to 0, which will avoid repeated prompts ("Do you want to weld coincident vertices?") when you are moving vertices. In case you do get such prompts, the answer is No. At this level, you can select any of the control vertices, or groups of vertices, and modify their positioning, type, and/or the placement of their control handles. To avoid opening up unwanted gaps in your patches, use window selection for vertex selection, rather than just clicking on a single vertex.
Going back to the first Edit Spline in the stack, select Sub-Object and then "Spline". A warning window appears; click "Ok". At this level, you can move or scale the crossection splines that make up the surface.
Any time you want to see the results of your edits in a shaded viewport, click on the "Show End Result Toggle on/off" icon; as long as the left mouse button is depressed, you will see the result of your edits. When you let go of the left mouse button, the viewport will return to wireframe.

Using a combination of these tools, modify the hat to your liking. Do this progressively, using "Hold" to preserve steps that you are satisfied with. Be particularly careful when moving handles, as their positioning should be viewed in 3 dimensions, not just two. Remember that you can modify vertex types; Bezier corners are often useful. If you want to change a vertex type, or a group of vertices, select them and then do a right mouse click. The different vertex type options will appear in the window that pops up.
___ While you can use movement in XY, I often find it safer to break those down into two moves, first along one axis, then the other. This takes more time, but it also makes it easier to keep things under control. Use the "Show End Result" toggle often to help you.

Figure 3 (click to see full size)

___ Figure 3 is provided as a guide. It resulted from rescaling (both uniform and nonuniform) some of the crossection splines, then moving control vertices to make the brim bend at the front (adjusting the handles to smooth the curving). The control vertices at the junction of the brim with the hat were turned into Bezier corners, to sharpen that angle. Finally, the handles of the crease's vertices were adjusted to smooth the crease itself. Conclusion The hat was modeled in about ten minutes. It is by no means an object that stretches Surface Tools' capabilities, nor is it a complete tutorial about this plugin. It is just meant to be a simple illustration of what the Tools can do for you.
___ With a little practise, you will soon get the hang of it, and enjoy Patch modeling.
___ Remember that you have the ability to display bitmap images in your viewports; this can be very helpful in building crossectional splines for complicated objects.

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3DS Max & Surface Tools

Revised: 30 Mar 98 rev 1
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