One of the most difficult effects to achieve in 3d animation is accurate and attractive cloth. From clothes to curtains, cloth is a desirable but very difficult material to simulate. In the following article we will look at and compare the three most popular cloth simulator plug-ins for 3dsMAX: Reactor, SimCloth3, and Stitch.

Reactor is a dynamics system designed by Havok for Discreet. It is included with 3dsMAX 5.0 for free. This system handles fluids, rigid bodies, soft bodies, rope, and cloth. Each of these are handled by the same simulation layout, which make it a powerful general use dynamics simulator. Reactor’s Cloth has a number of controls to adjust the movement of the cloth. There are 2 models for calculating the forces on the cloth. These are the simple force model, and the complex force model. While the simple force model is faster, it does a poor job of simulating fabric based cloth. The cloth created by the simple force model looks rubbery like latex. The complex force model takes longer to simulate, but has much more accurate movement. There are additional controls regarding how the cloth folds, self collisions, and vertex based controls. The vertex based controls are a useful feature but are limited compared to Stitch. Additional options are common to all Reactor simulations and include values such as gravity and iterations per second. Reactor Cloth has a very satisfactory simulation engine and feature set, especially being a free plug-in with 3dsMAX 5.

SimCloth3 is a free plug-in developed by the Chaos Group. Before Reactor in 3dsMAX 5, this was the only good free cloth simulator for 3dsMAX. SimCloth3 has the most simple and straight forward workflow the three simulators tested in this article. However, the drawback is that it is the most limited as well. There does not seem to be any way to simulate air resistance, which greatly reduces the realism of the simulation. Also, even with SimCloth3’s more advanced force and bending models, the cloth looks rubbery. SimCloth3 is also by far the slowest of the 3 simulators looked at in this article. While it can handle low polygon count simulations quickly and easily, simulations above a few thousand polys quickly bog it down.
One major advantage SimCloth3 has over Reactor and Stitch is that it is open source. SimCloth3 is protected by the GNU General Public License, which essentially states that you can use the source to modify the software. However, you must also release the source code along with any products based off of SimCloth3. For larger studios, used to writing custom software, SimCloth3 gives an infinitely customizable solution.
A major complaint lies in SimCloth3’s stability. SimCloth3 crashed 3dsMAX a number of times during testing. This greatly reduces its usability in a production environment. However, SimCloth3 is still considered to be in beta and may be fixed in later releases

Stitch is a cloth simulator for 3dsMAX developed by Digimation. This plug-in is not free. However, from the comparisons tests, you will see that you get what you pay for. There are 2 components to Stitch: Garment Maker and Stitch. Garment Maker is a plug-in designed to create clothing. It allows you to ‘sew’ flat cut outs of material together into full items of clothing. This allows you to create clothing much like it is created in the real world. It gives the clothing seams and other small details that can not be achieved with a simple editable mesh. These GarmentMaker based clothes only work with Stitch’s cloth simulator however.
The stitch modifier is the second component of the Stitch plug-in and performs all of the cloth simulations. Stitch contains the same type of controls as Reactor Cloth and SimCloth3, but with far more freedom into customizing the cloth as a specific fabric. There are more than 20 controls for adjusting the look and movement of the cloth. To make these controls less intimidating, a number of presets are accessible from a pull down menu. These presets include burlap, cotton, leather, rubber, silk, and wool among others. There are also more than a dozen controls based on vertex level adjustments. You can select vertices much like the edit mesh modifier (including soft selection) and control the flexibility and other values based on the selected vertices. This gives infinite control to how the cloth bends and reacts to air resistance or collisions with other objects. There is also a feature called Live Drag! which allows you to push and pull the cloth while it is being simulated. This is invaluable when arranging clothing onto a character, or getting the look of ruffled cloth just right.

Head to Head Comparisons
Stitch has by far the most powerful and robust feature set, however, real world performance is what counts. Following is a head to head comparison of Reactor Cloth, SimCloth3 and Stitch. To make this comparison fair, GarmentMaker was not used in any of the simulations. All of the tests are using simple primitives or editable meshes.

The first test involves a very low polygon count scene of 112 faces. All three simulators performed the test quickly and easily. Below is a link to the resulting animation. Judge for yourself which simulator is more accurate.


Click image above for animation

To test a more complicated scenario a medium polygon count scene was created. This scene contains 4520 faces. With these extra polygons, the simulators slowed down considerably. Each simulator was adjusted to get as close to real looking cloth as possible. A flexible, but quickly settling cloth is ideal. Stitch came the closest to this look with its default values. With Reactor, the defaults were changed to more accurate models and a number of other adjustments were made. SimCloth3 also required a number of adjustments, but without any wind resistance, it was not possible to reduce the settling time of the cloth.
Below is a graph showing the time needed to simulate these medium complexity scenes

In this scene Stitch performed more than 5 times faster than Reactor, and more than 8 times faster than SimCloth3. Below is the animation of the simulation. Observe the high settling time of SimCloth3, and the rubbery bounce in the Reactor Cloth simulation. Stitch had the most flexible cloth with the lowest settling time.



Click image above for animation

For a real world test, motion capture data was imported into character studio to animate a woman wearing a dress. This scene contained about 20,000 faces in the cloth simulation. The image below shows the edged faces view of the model used for animation.

SimCloth3 took about 20 minutes to perform the simulation. However, when the animation was viewed, the dress had been erased from the scene. A number of settings were tweaked to help the simulator, but to no avail. It seems that this scene was too complex for SimCloth3. Reactor had similar issues. After 2 or 3 frames into the simulation, the dress ‘exploded’. This ‘explosion’ is a common side effect of soft body dynamics simulators breaking. It is caused by the spring and dampening values conflicting with the simulator’s limits. A number of different settings were tried with Reactor, but it refused to simulate. Stitch was the only plug-in which performed the simulation without any issues. After some tweaking and adjustments, a satisfactory simulation was obtained in about 7 minutes of calculation time. The below animation shows the result.


Click image above for animation

Conclusion
As these tests show, Stitch is by far the best cloth simulator of the 3 compared. However, it is not a free plug-in and you will have to pay for the additional speed, stability, and accuracy. Of the free plug-ins, Reactor stands out because if its stability and accurate simulation. SimCloth3 could not handle complicated scenarios and was unable to simulate any fabric. For now it is limited to rubbery materials with no air friction.
For large studios willing to put in the time to customize and edit the software, SimCloth3 is worth looking into. For 3dsMAX users on a tight budget, needing simple cloth simulations, Reactor’s Cloth will do the job. However, for studios and artists willing to pay for a professional level cloth simulator, Stitch is hands down the best cloth simulator available for 3dsMAX.