Adjusting nParticle Shading attributes

By adjusting nParticle Opacity, you can mimic the way smoke disappears into the air as the nParticles age. You can then set the Color ramp to add shades of white, gray, and blue to the smoke.

Like the nParticle Radius attribute, Opacity and Color can be set on a per nParticle object or per-particle basis. Using the nParticle object's Shading ramps, you can map per-particle Opacity and Color to nParticle properties such as particle Age, Particle ID, and Radius.

To set nParticle Shading attributes

1. To make it easier to see the changes you make to the nParticle object’s Shading attributes, you can hide the Volume Axis field shape by selecting Field_Smoke1 in the Outliner then selecting Display > Hide > Hide Selection.

   The Volume Axis field still affects your nParticles, but you no longer see the volume shape in the scene view.

2. In the Outliner, select nParticle_Smoke.
3. In the Attribute Editor, click the nParticle_SmokeShape tab.
4. In the Shading section, set Opacity to 0.1.
5. Play the simulation.

   Notice that the emitted nParticle cloud appears thinner and more like cigarette smoke than before.

   To further improve the appearance of the smoke as it rises and dissipates in the air, you can use the Opacity Scale ramp to adjust the opacity of individual nParticles as they age.

6. In the Opacity Scale section, click in the ramp to create additional markers then set an Opacity ramp by setting the following marker settings:

   Marker	Selected Position	Selected Value	Interpolation
   1	0.299	0.980	Spline
   2	0.560	0.915	Spline
   3	0.709	0.580	Spline
   4	0.984	0.0	Spline

7. Set Opacity Scale Input to Normalized Age.

   As each nParticle ages from birth (emission), its opacity changes from the opacity values specified by the left marker to the one specified by the right marker.

8. Set Opacity Scale Randomize to 0.116.
   
9. To set the color of the nParticles when they are first emitted, click the far left circle marker of the ramp (at Selected Position 0) then click the color swatch beside Selected Color.

   The Color Chooser appears.

   
10. Select HSV from the list in the bottom right corner of the Color Chooser.
11. Either use the sliders to select a white color with a little grey, or type the following color values into the HSV (Hue-Saturation-Value) fields:
    • H:210
    • S: 0
    • V: 0.95
12. Drag your mouse off the Color Chooser to close it.
13. To set the color of the nParticles as they continue to age, click inside the ramp to create a marker, set the Selected Position to 0.834, then click the color swatch beside Selected Color.
14. In the Color Chooser, type the following color values into the HSV (Hue-Saturation-Value) fields:
    • H:210
    • S: 0
    • V: 0.75
15. Select the far right marker of the ramp (at Selected Position 1.0) and set the color to the following color values into the HSV (Hue-Saturation-Value) fields:
    • H:191
    • S: 0.084
    • V: 0.85
16. Set Color Input to Normalized Age.

    As each nParticle ages, its color changes from the color specified by the left marker to the one specified by the right marker.

17. To improve the way the nParticles colors blend as they age, do the following:
    • Set Interpolation to Smooth for each marker.
    • Set Color Randomize to 0.5.

    When you play the simulation, the nParticles look more like cigarette smoke.

    Adding more volume to the smoke would further improve the simulation. Instead of reducing the nParticle Opacity values, you can emit more particles and increase the nParticle Radius to create more smoke volume.

    

To add volume to the nParticle smoke

1. In the Outliner, select nParticle_Smoke.
2. In the Attribute Editor, click the nParticle_SmokeShape tab.
3. In the Lifespan section, set Lifespan to 10.
4. In the Particle Size section, set Radius to 6.5.
5. In the Attribute Editor, click the Emitter_Smoke1 tab.
6. In the Basic Emitter Attributes section, set Rate (Particles/Sec) to 128.4.
7. Play the simulation.

   You can continue adjusting the Opacity Scale and Color ramps to create the exact dissipation effect and color you want for the smoke.