Convert nParticles to a polygon mesh

To create a smooth surface for your liquid simulation, you can convert the nParticles to a polygon mesh. Converting nParticles to a mesh has many advantages, because you can edit it like any other polygon object.

For example, you can improve the quality and overall look of your liquid simulation by performing polygon smooth operations on the output mesh. Polygon smoothing increases the number of polygons in your mesh and gives it a smoother appearance. For your liquid simulation, this helps create a smooth, continuous surface, like the surface of water. See nParticle output meshes in the nDynamics guide.

Before converting the nParticles to an output mesh, you can set the initial state of your simulation to an advanced frame. Doing this ensures that the nParticles have settled down to the bottom of the pitcher before its animation starts. From frames 1 to 30, Nucleus gravity and the initial collisions between the nParticles and the inside wall of the pitcher cause the particles to move. For a realistic effect, you want the water to be motionless at the bottom of the pitcher at the start of the simulation.

To set the initial state of the nParticles

1. Play the simulation and stop the playback at or around frame 30.
2. In the Outliner, select nParticle_Water.
3. Select nSolver > Initial State > Set From Current.
   
4. Rewind to the start frame and play the simulation.

   If you are not satisfied with how the particles behave in the new initial state, for example they may be still moving in the pitcher, play the simulation for 20 to 30 frames and set the initial state again. Continue setting the initial state until you are satisfied with the results.

To convert your nParticle object to a polygon mesh

1. In the Outliner, select nParticle_Water.
2. Select Modify > Convert > nParticle to Polygons.

   After your nParticle object is converted to a polygon object, Maya no longer displays the particles in the scene view. This reduces simulation time and makes it easier to see how your Output Mesh attribute adjustments affect the mesh.

   The polySurface1 object appears in the Outliner, and a new polySurfaceShape node appears in the Attribute Editor.

   Note

   To make the nParticle object visible in the scene, in the Object Display section of the nParticle_WaterShape node in the Attribute Editor, turn off Intermediate Object.

3. In the Outliner, rename the new polySurface1 polygon object to Water_Mesh.
4. In the Attribute Editor, select the nParticle_WaterShape tab.
5. In the Output Mesh section, set Blobby Radius Scale to 3.5.
   
6. In the Output Mesh section, select Quad Mesh from the Mesh Method list.

   Selecting Quad Mesh creates your converted mesh using quad-based polygons, while Tetrahedra, Triangle Mesh, and Acute Tetrahedra create meshes using triangulated polygons. Output meshes that are quad-based respond better to polygon smoothing (Mesh > Smooth) than triangle-based output meshes.

   
7. Dolly and tumble the scene so that you can closely observe the nParticle output mesh, and experiment with the following Threshold values.
   • Set Threshold to 0.2.

     At this value, the nParticle output mesh extends beyond the nParticle object’s collision width and penetrates the inner wall of the pitcher mesh.

     
   • Set Threshold to 1.5.

     At this value, holes appear in the Particle output mesh because some nParticles are no longer overlapping.

     
   • Set Threshold 0.6 and continue.
8. Set Mesh Triangle Size to 0.2.

   This setting determines the size of the triangles that are used to create the mesh. Small values produce higher resolution meshes with smoother surfaces. Be aware that higher resolution meshes take more time to simulate.

9. To apply smoothing to the corners of the mesh’s quad, set Mesh Smoothing Iterations to 3.
   

   The output mesh is noticeably smoother.

10. Play the simulation.