Applying a nCloth preset to the shirt

When you play back the simulation, you notice the following:

• Around frame 1033, the shirt collar is stretching too much to resemble the fabric it's trying to emulate.
• At frame 1033, some of the shirt’s vertices are self trapped within the object, and interpenetrations between the shirt and pants appear around the characters waist. This is caused by inaccurate collisions between the nCloth shirt and nCloth pants objects.

  

• At frame 1037, the shirt is riding too high on the character’s body and the polygon faces in the front of the shirt are deforming poorly.
• Between frames 1040 and 1098, some of the shirt’s vertices are becoming trapped within the object, and there are interpenetrations.

  

A useful way to solve a number of these simulation problems simultaneously is to apply an nCloth attribute preset to the nCloth shirt object.

To apply an nCloth preset to the shirt

1. In the scene view, select the nCloth shirt.
2. In the Attribute Editor, select the nCloth_ShirtShape tab.
3. Click-hold the Presets button.
4. Select the tshirt preset, and then Replace (tshirt > Replace).

Some important attributes adjustments made by the t-shirt preset are the following:

• Stretch Resistance is adjusted from 20 to 35.
• Bend Angle Dropoff is adjusted from 0 to 0.4

  Bend Angle Dropoff adds resistance to bending forces in response to the strength of the bending force. In the simulation, Bend Angle Dropoff effectiveness in reducing the nCloth tendency to bend can be observed when the nCloth shirt is beginning to bundle up at frame 1032.

• Mass is adjusted from 1.0 to 0.6.

  The reduction in Mass reflects the light to medium weight material of a cotton t-shirt.

• Damp is adjusted from 0.0 to 0.8.

Wrapping the high resolution mesh

In this section of the lesson, you use a wrap deformer to create an influence object for the high resolution shirt.

To wrap the high resolution mesh

1. In the scene view, show the Shirt_HighRes object by selecting it in the Outliner, and then selecting Display > Show >Show Selection.
2. -select the nCloth shirt object.
3. From the Animation menu set, select Create Deformers > Wrap.

   A wrap node appears in the Attribute Editor, and a Shirt_LowResBase object appears in the Outliner.

   

4. In the Attribute Editor, click the wrap2 tab.
5. In the Wrap Attributes section, turn on Exclusive Bind.
6. Hide the Shirt_HighRes object, and play back the simulation.

Identifying problem areas in the simulated nCloth

When you play back the simulation, you notice the following:

• At frame 1032, the excessive stretching around the shirt's collar is reduced. However, this area of the nCloth is still stretching too much.

  

• At frame 1033, in the waist area, some previous instances of self trapped vertices have been resolved, however some interpenetrations still remain.
• Between frames 1039 and 1049, in the chest area, the shirt deformations have improved, but the polygon faces still protrude too far outward to resemble the realistic behavior of a t-shirt.

  

The nCloth t-shirt preset has improved many of the simulation issues, however some Dynamic Properties attributes need further adjustment.

When editing the Dynamic Properties attributes, cache your simulation and then play it back between attribute adjustments to see how your new settings affect the nCloth shirt's behavior. For comparison purposes, you can also display the reference character in the scene. To do this, in the Display Layer Editor, turn on Visible.

To edit the shirt’s Dynamic Properties

1. In the Attribute Editor, click then nCloth_ShirtShape tab.
2. In the Dynamic Properties section, make the following settings:
   • Stretch Resistance: 55
   • Compression Resistance: 3
   • Bend Resistance: 0.3

     

3. Cache your simulation, and play it back.

Editing the Quality Settings and resolving interpenetrations

When you play back the simulation, you notice the following:

• Between frames 1028 and 1034, around the character's waist, there are areas where the pants and shirt no longer overlap. This exposes the nRigid_Body object, which might be a desired result.

  

  The offset between the nCloth object occurs because the collision Thickness is currently set to accommodate the high resolution wrap deformer. Reducing Thickness may solve this issue, but be aware that interpenetrations can result from such an adjustment. For the purposes of this tutorial, Thickness is left at its present value.

• At frame 1042, there are still too many quads bunching up in the shirt at the character’s chest, causing interpenetrations. Although this behavior can be considered realistic, reducing interpenetrations in this area would make the shirt’s more realistic.

  

To smooth the mesh and reduce instances of interpenetrations, edit the Collisions and Quality Settings.

To edit the Collisions and Quality Settings

1. In the Attribute Editor, select the nCloth_ShirtShape tab.
2. In the Collisions section, set the Self Collision Flag to Full Surface.
3. In the Quality Settings section, set the following:
   • Max Iterations: 12000.
   • Max Self Collision Iterations: 8.
   • Turn on Trapped Check.
   • Turn on Self Trapped Check.

     

4. Cache the simulation and then play it back.

   

Fine tuning the simulation

To further improve the quality of the simulation and reduce the instances of interpenetration in problem areas, such as the bunching of the shirt in the chest area (see frame 1040) you can set Push Out and Push Out Radius. Try setting the attributes values between the following ranges:

• Push Out: 0.1—20
• Push Out Radius: 10—50

Experiment with your settings by creating duplicates of the meshes at specific frames of the simulation. For example, create mesh duplicates at frames 1040 and 1043. Cache the simulation, and then scrub through the Timeline and compare your simulation with your duplicate mesh to see the results of your attribute edits.

Comparing the final low resolution simulation with the simulated reference character mesh

In the section of the lesson, you compare the final simulation result of the nCloth shirt and nCloth pants objects with the simulated reference character object (the original simulated high resolution mesh).

To compare the simulations

1. Hide the Shirt_LowRes and Pants_LowRes objects, selecting by selecting them in the Outliner, and then selecting Display > Hide > Hide Selection.
2. Show the Shirt_HighRes and the Pants_HighRes objects by selecting them in the Outliner, and then selecting Display > Show >Show Selection.
3. If you have not done so already, using the Displays Layers Editor, turn on Visible to display the Reference_Character object in the scene view.
4. In the Shading menu, turn off Wireframe on Shaded.
5. Scrub through the Timeline, to compare how nCloth meshes behave in the animation. Dolly and tumble the scene so that you can closely observe the problem area.

   

   

There are subtle differences between the way both the high resolution and reference character objects simulate, but overall the nCloth behaves in similar ways. Considering the amount of time saved of repeatedly working through the simulation workflow of caching the simulation and adjusting attributes on the low resolution mesh, the low resolution mesh workflow provides good results. Although the reference character object can be improved by optimizing the simulation, however, the higher resolution mesh would slow down caching and simulation time and might require more attribute adjustments.