Modeling with the Snapshot Tool

Ted Boardman tedb@tbmax.com         http://www.tbmax.com


Not much more snow has fallen this month, but there certainly isn’t much less out there, either. It’s not bad though; I drive a VW GTI (small car) and am able to use the snow-covered driveway to my advantage. I back quickly out of the garage, slam on the brakes, and spin the steering wheel quickly while I shift from reverse to first. In one motion I’m at the end of my driveway, headed out. It makes any passengers a little woozy, but I get a kick out of it.

I also get a kick out of using the Snapshot tool in max and VIZ. It’s an underutilized command that has been around for quite a while, which is a shame because it can be an interesting way to model, although that’s not what it was necessarily designed to do.

This month I’ll show a couple of examples of how I use Snapshot. The prime function is useful both max and VIZ, but some other examples are only usable in max 4 or 5. Learn what it does and you should be able to develop new ways of working with it, too.

What is Snapshot

Snapshot was a tool that was an extremely powerful way to create complex arrays of objects and I still find it useful in that roll. Simply put, if you have an animated object you can take snapshots of the object at frames of it’s animate to create clones. A good example would be a line of fence posts that wind up over a hill.

Create a path over the hill and animate one post to travel along the path. TIP: use Constant Velocity and/or Normalize Spline if you want equally spaced posts. Once animated, go to Tools, Snapshot and set the number of clones you want. Viola’, a row of fence posts appear along the path. The original animated post is still in the scene so you would have to delete it, usually.

An example of where I have used Snapshot in this manner is for a piece of artwork that was hanging in a clients lobby that they were not looking forward to reproducing in max because of the handwork involved. It consisted of a column of cloth triangles on a wall that were spaced equally and each was rotated slightly to create a fan effect projecting from the wall.

The easy solution was to animate one triangle moving and rotating 180 degrees up the wall. Then use Snapshot to make each copy. Figure 1 shows an example of what I mean with 20 clones. No math or calculations required.

Figure 1: Reconstructed artwork using one animated triangle and the Snapshot tool.

Snapshot can be used in max and VIZ to help reduce the overhead caused by Displacement Mapping, too. In an example of a mountainous landscape, I used a Swirl map in the Displacement slot of a material and applied it to a dense Plane primitive in the scene. See Figure 2 for the resulting landscape.

Figure 2: Complex landscape made from Displacement Map and Snapshot for an mesh that can easily be optimized. TIP: the appearance of the sun backlighting the mountains is enhanced by applying a Falloff map in the Self-Illumination slot of the landscape material.

In order to see the mesh in the viewport while working, I had applied a WorldSpace *DisplaceMesh modifer. The overhead of the dense mesh and the calculations of DisplaceMesh can slow the workflow for the fastest machines and Collapse doesn’t work on WorldSpace modifiers.

Snapshot came to the rescue again. Once I had the landscape adjusted to my liking, I used Snapshot to create a single new Mesh; a clone won’t gain anything in this case. I could then delete the original and apply and Optimize modifier to the new mesh to reduce the density to a manageable and visibly acceptable level.

In my newest book, 3ds max 5 Fundamentals by New Riders, I use Snapshot to make copies of a bird’s wing that can be used as morph targets. The process uses a Quadpatch that has been modified to represent the flow of air under a bird’s wing as it flies. The wing then gets a *PatchDeform WorldSpace modifier to cause it to deform to the surface. I then move it across the surface and make Snapshots of the wing in various positions. While VIZ doesn’t have object morphing capabilities, this method can still be use to generate some very complex objects that might otherwise be difficult to model.

Use of Snapshot with 3ds max

There are some applications of Snapshot that are only valid in 3ds max 4 and 3ds max 5. For example I needed to create some icicles recently (see Figure 3). I started with a SuperSpray particle system that was set to MetaParticles with a large Size setting and a slow Speed setting and the display set to 100 percent of the particles. See Figure 4 for the relevant settings for my example. When I had the object to my liking, I used Snapshot for a mesh copy for my scene.

Figure 3: Icicles outside a window created from a SuperSpray particle system and Snapshot.

Figure 4: The basic SuperSpray settings to create a reasonable icicle.

All sorts of random static masses could be created with the combination of Particle Systems and Snapshot. For example, rather than the overhead of a particle system waterfall, you might be able to create the water with the particle system, snapshot a copy, and apply an animated material for a much less intensive solution than the “live” particles. Or, perhaps a rock cliff or smoke from a chimney, once you know the potential you should be able to come up with your own uses.

Reactor and Snapshot in 3ds max 5

Reactor, the dynamics tool that is included in 3ds max 5 is primarily considered a special effects tool and, for that reason, I have seen only limited use of it in production environments to date. However, using it in combination with Snapshot opens a new world of possibilities for general use.

I taught an advanced modeling class recently at Virtual Partners in Green Bay, WI http://www.virtualpartners.com for a company that creates the glass blocks with laser cut objects inside. They are often given as trophies or gifts by companies to their best customers or employees and may contain scenes a diverse as game fish, sports figures, vehicles, buildings, or company logos.

The process is to generate a 3d model of the object with the necessary detail, then to process the model in software that reads the xyz surface data and translates it into code that the laser cutters can use to melt a void in the glass, leaving what appears to be a wire frame model inside.

One of the objects that is popular with them these days is flags of various kinds and they were not happy with the results or the time involved in using FFD modifiers, SoftSelection methods, or Patch objects to generate natural looking folds. I wasn’t sure if Snapshot worked on objects with Reactor solutions, but thought it was easy enough to find out.

Here I’ll give two examples of solutions that fit their needs explicitly, saving much production time and resulting in a better looking mesh. One example is a flag hanging from a flagpole at an angle as if it were mounted on the side of a building. The other example is the canvas top on a covered wagon like the Conestoga wagons that roamed the western plains of the US and Canada. The same techniques could be used to create bedspreads, tablecloths, drapes, and clothing for characters.

The method uses the reactorCloth modifier and rigid bodies in the scene.

A Covered Wagon

In this scene I lofted an Ellipse along a path to create a bow that would support the canvas top of a covered wagon. I then arrayed it to make three copies.

The canvas top is a Plane primitive with 30 Length and Width segments that has been placed about 2 feet above the bows in the scene. See Figure 5.

Figure 5: Four lofted bows with a 30 x 30 segment Plane placed about 2 feet above. Two Reactor objects can be seen to one side of the mesh objects.

1. From the Create, Helpers, Reactor menu choose RBCollection and pick in a viewport. Then click CLCollection and pick near it in the same viewport. This creates the necessary Reactor objects.
2. Select the Plane and, in the Modify panel, Modifier List, choose reactorCloth. The default settings will be fine to start.
3. Select the RBCol object and, in the Modify panel, click the Add button. Choose the bow objects from the list. Do not add the Plane object. This lets reactor know these objects are classified as Rigid Bodies.
4. Select the four bow objects in the scene and go to Utilities panel, Reactor, Properties. Near the bottom of the panel, in the Other Properties area, check the Unyielding option. This tells the bows not to react to gravity and not to move when struck by other reactor objects.
5. Select the CLCol object in the viewport and, in the Modifiy panel, pick the Add button, and choose Plane in the list. Plane will not show in the list if you have not applied the reactorCloth modifier in step 2.
6. In the Utilities panel, Animation & Export rollout, check Update Viewports and click the Perform Simulation button. Reactor gravity will pull the Plane into contact with the bows and the dynamics will deform the cloth over them.
7. When the simulation is complete, drag the Frame Slider to a frame where the cloth looks the way you want and use Snapshot from the Tools pull-down menu to create a new Mesh object.
8. You can then trim and modify the new object as you would any other mesh.
9. You can also change the parameters in the reactorCloth modifier for to adjust for weight, air resistance, stiffness, etc for a different draping effect. Then run the simulation again.

See Figure 6 for the result of my example with some of the Cloth settings.

Figure 6: Settings and resulting mesh generated quickly with Reactor Cloth. Snapshot can be used at one or more frames to create various mesh objects.

A Draped Flag

This scene is similar and has four objects: a Cylinder flagpole, a Plane flag, a RBCollection, and a CLCollection. This exercise has an extra process and modifier that allows you to attach one side of the flag to the flagpole.

The flagpole must be added to the RBCollection and it’s properties must be set in Utilities panel to be Unyielding so it won’t fall with gravity. The flag Plane, that has 30 segments in each direction, has the reactorCloth modifier applied, then is added to the CLCollection.

You must then apply a MeshSelect modifier to the Plane, go to sub-object Vertex and select the row of vertices closest to the flagpole. While still in Vertex sub-object mode, apply a reactorAttachToRB modifier and choose the flagpole as the Rigid Body object. I apply a new MeshSelect to that to return control back to the whole plane. It’s not necessary for this example, but is a good habit to get into.

Perform the simulation in the Utilities panel, Reactor panel, Animation & Export rollout. When the simulation is complete use Snapshot to copy one or more draping flags to new Mesh objects. See Figure 7 for an example showing my reactorCloth settings and the end results.

Figure 7: ReactorCloth example using reactorAttachToRB modifier to restrain the edge of the flag to the flagpole.

Summary

You now have a good reason to “play” with Reactor, no matter what your application of 3ds max 5 is (or 3ds max 4 with the Reactor plug-in) is. You also have some new modeling weapons in your arsenal that will work in both 3ds max and VIZ. The key to the process is the old standby called Snapshot that often never gets the respect it deserves.

Try experimenting and see what you can come up with for variations using the other Reactor tools like Water, Soft Bodies, and Rope collections.

Good luck and have fun.

Ted

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