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Lesson 3: Creating a liquid simulation with nParticles

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Learning Resources > Tutorials > Getting Started with Maya > nParticles > Lesson 3: Creating a liquid simulation with nParticles > 

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.

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 the simulation to the start frame.

To convert your nParticle object to a polygon mesh

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

   The PolySurface1 object appears in the Outliner, and a new polySurfaceShape node appears in the Attribute Editor.

3. Rename the new PolySurface1 polygon object to Water_Mesh in the Outliner.

   

4. In the Attribute Editor, select the nParticle_WaterShape tab.
5. In the Output Mesh section, set Blobby Radius Scale to 3.5.

   

   In the scene view, the nParticle output mesh is superimposed over your nParticle object.

6. In the Output Mesh section, select Quads from the Mesh Method list.

   Selecting Quads creates your converted mesh using quad-based polygons, while Tetrahedra, Cubes, and AcuteTetrahedra 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, the nParticle output mesh cuts into the nParticle object, and no longer surrounds the nParticles.

     

   • Set Threshold 0.6.

     

8. Set Mesh Triangle Size to 0.2.

   This setting determines the size of the triangles 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 quads, set Mesh Smoothing Iterations to 2.

   

   The output mesh is noticeably smoother.