In this lesson, you set up the particle geometry to change over time as the smoke disperses. You also set up the Particle Flow system so it uses fewer particles.

Set up the scene:

1. Continue from the previous lesson or open pflow_01.max.

Change the particle geomery:

1. Restore Particle View (6).
2. Click the Birth 01 operator to highlight it, then change the Amount of particles emitted to 250.
   
3. From the depot, drag a Shape Facing operator, and drop it on top of the Shape operator, to replace the Shape operator with Shape Facing.
   

   Unlike the blue line that appears when you add an operator by dropping the operator between two others, the line for replacing an operator appears red.

   

   In viewports, the particles change to square shapes that are larger than the small cubes you generated before. However, their orientation is random: This is because the particles aren’t yet oriented to anything.

4. Move Particle View so you can see a viewport with the camera visible in it. (The lower-left Orthographic view is good for this.)
5. Click the Shape Facing operator to highlight it.
   
6. On the Shape Facing operator rollout, click to turn on the Look At Camera/Object button (at present it is labeled “None”), then in the viewport, click Camera01.
   

   Click the Look At button to turn it on.

   

   Look At button after you pick the camera

7. Hide Particle View (6).
8. Drag the time slider.

   Now particles face in a uniform direction, and always face the camera, as you can see most easily in the Perspective viewport.

   

   Shape facing particles always face another object. Usually this is a camera: The idea is to assign the particles a material that makes the scene geometry appear to be more complicated than it actually is. (The tutorial Particle Trees is another example of this technique.)

9. Restore Particle View (6).
10. In the Shape Facing parameters rollout Size/Width group, make sure In World Space is chosen, and then change the value of Units to 5.0.
    

    Now when you drag the time slider, smoke particles are easily visible even in the Camera01 viewport.

    

Set the particles to grow over time:

The smoke particles should grow over time: As the smoke rises, it also disperses. To model this, you use a Scale operator.

1. Drag a Scale operator from the depot to Event 01, and drop it between the Shape Facing and Force operators.
   
2. Click the Scale operator to highlight it.
   
3. In the Scale parameters, choose Relative Successive from the Type drop-down list.
   
4. Make sure Constrain Proportions is turned on, then change the value of Scale Factor X % to 100.2.
   

   Because Constrain Proportions is on, the Y % and Z % factors update to 100.2 as well.

   The factor by which the particles grow doesn’t need to be great. Even two-tenths of a percent increase at each frame adds up quickly.

5. Hide Particle View (6) and drag the time slider.

   The particles increase in size as they rise.

   

Create a dynamic material for the particles:

The next step is to create a material that changes over time while the particles change in size.

1. On the main toolbar, click (Material Editor) to display the Slate Material Editor.
   TipIf this is the first time you have used the Slate Material Editor, you might have to resize it to make it larger so you can easily see all the panels.
2. In the Material/Map Browser panel on the left, locate Materials Standard Standard, and drag the Standard material entry into the active View.
   
3. In the active View, double-click the Standard node so you can see its parameters on the Parameter Editor panel to the right.
   
4. Name the new material Smoke.
   
5. On the Material/Map Browser panel, locate Maps Standard Particle Age, and drag the Particle Age entry into the active View.
   
6. In the active View, wire the Particle Age map output to the Standard map’s Diffuse Color input.
   
   NoteWhen you wire the Particle Age map, 3ds Max also adds a Bezier Float controller node. You won’t be using that in this tutorial.
7. Double-click the Particle Age map node to display its parameters.
   

   The Particle Age map specifies three colors: By default, Color #1 is the color at a particle’s birth (0 percent), Color #2 is the color when the particle is halfway through its life (50 percent), and Color #3 is the color at the particle’s death (100 percent). You can change the ages, but we won’t do so in this tutorial.

8. Change Color #1 to yellow, Color #2 to green, and Color #3 to blue.
   

   Don’t worry about the precise values: These are just arbitrary colors to test the Particle Age effect. Once Particle Age is working as we want it to, you will replace the colors with more realistic patterns.

9. In the Material/Map Browser panel, scroll so you can see the Sample Slots group. Drag from the output socket of the Smoke material node (at the right), and drop it on an unused sample slot. In the Instance/Copy dialog, choose Instance, then click OK.
   

Add the new material to the particle system:

1. Minimize the Slate Material Editor and restore Particle View (6).
2. Drag a Material Dynamic operator from the depot, and drop it on Event 01 between the Force and Display operators.
   
3. Click the Material Dynamic operator to highlight it.
   
4. In the Material Dynamic parameters, click the Assign Material button.
   

   3ds Max opens a modal version of the Material/Map Browser.

5. Scroll to the Sample Slots group, and double-click the Smoke material.
   
6. Hide Particle View (6).
7. Activate the Camera01 viewport, click (Go To End), and then click (Render Production).
   NoteThe Particle Age effect doesn’t appear in viewports, so when you use this map, you have to render to see the result.
   

   The particles still have a uniform yellow (birth) color.

   The reason for this is that the particles don’t yet have a defined life span. The Birth operator controls particle creation, but not particle death.

Define the life span of particles:

1. Restore Particle View (6).
2. In Particle View, drag a Delete operator from the depot, and drop it on Event 01 between the Birth and Position Icon operators.
   
3. Click the Delete operator to highlight it.
   
4. In the Delete parameters, choose Remove By Particle Age.
   

   Choosing By Particle Age enables the Life Span and Variation parameters.

   
5. Change the value of Life Span to 350 and the value of Variation to 50.
   

   The Variation setting introduces a random variation in the life span of particles, so the system doesn’t appear too uniform.

6. Hide Particle View (6).
7. Render frame 300 once again.
   

   The particles begin with a yellow color, which shades to green at their half-life, and then to blue as they near the end of their existence.

Now you are ready to change the particle colors from the test colors to a pattern that simulates smoke. This is the subject of the next lesson.

Save your work:

• Save the scene as smoke_dispersing.max.