Rendering menu > Environment > Environment and Effects dialog > Environment panel > Atmosphere rollout > Add > Fire Effect
Use Fire to produce fire and smoke effects. Possible uses for Fire effects include campfires, torches, fireballs, clouds, and nebula.
Note: In earlier versions of Autodesk VIZ, Fire was known as the "Combustion effect."
You can add any number of fire effects to a scene. The order of effects is important because effects near the bottom of the list are layered in front of effects near the top of the list.
Each effect has its own parameters. When you select a fire effect in the Effects list, its parameters appear in the Environment dialog.
Fire renders only in Camera or Perspective views. Orthographic or User views don’t render Fire effects.
Tip: Fire doesn't support completely transparent objects. Set the transparency of Fire objects accordingly. Use visibility rather than transparency to make Fire objects disappear.
Note: The Fire effect does not cast any light or shadows in the scene. To simulate illumination, you must also create lights. To cast shadows, you need to go to the Shadows Parameters rollout of your lights, and turn on Atmosphere Shadows.
Example: To create a campfire:
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Click Helpers on the Create panel and choose Atmospheric Apparatus from the subcategory list.
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Click Sphere Gizmo. Drag the cursor in the Top viewport to define an apparatus radius of about 20 units. Turn on the Hemisphere check box in Sphere Gizmo Parameters.
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Click Non-Uniform Scale. Click Yes in the Warning dialog (this warning doesn't apply to atmospheric gizmos), and scale the apparatus 250 percent along its local Z axis only. You can then model logs, embers, and rocks around the base of the apparatus.
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Open the Modify panel of the Sphere Gizmo. On the Atmosphere rollout, click Add and choose Fire from the Add Atmosphere dialog.
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Highlight Fire in the Atmospheres list under the Atmospheres & Effects rollout. Click Setup.
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Set the following parameters under Shape and Characteristics:
The Fire effect doesn’t cast any light in the scene. If you want to simulate illumination from the fire effect, you must create lights as well.
You create a fire apparatus, or "gizmo," to position the effect in your scene and to define the maximum boundaries of the effect. The apparatus is a Helper object found in the Atmospheric Apparatus subcategory.
There are three kinds of apparatus: BoxGizmo, SphereGizmo, and CylGizmo..
You can move, rotate, and scale the apparatus, but you cannot apply modifiers.
Using non-uniform scale is a good way to change the shape of the apparatus for effects. (You will see a warning when you use this transform. Because you don't modify atmospheric apparatus, you can safely ignore the warning.)
You must assign an atmospheric apparatus to a fire effect before you can render the effect. Use buttons in the Gizmos area to manage the list of apparatus objects.
Pick Gizmo—Click to enter Pick mode and click an atmospheric apparatus in the scene. The apparatus displays the fire effect when you render. The name of the apparatus is added to the apparatus list.
Multiple apparatus objects can display the same fire effect. For example, torches on a wall can all use the same effect. Assign a different seed to each apparatus to vary the effect.
You can assign single apparatus to multiple fire effects. For example, one apparatus can display both a fireball and a tendril flame effect.
You can choose multiple gizmos. Click Pick Gizmo and press H. This displays a Pick Object dialog on which you choose multiple objects from the list.
Remove Gizmo—Removes the gizmo selected in the gizmo list. The gizmo remains in your scene but it no longer displays the fire effect.
Gizmo List—Lists apparatus objects assigned to the fire effect.
You can set three color properties for a fire effect using the color swatches under Colors. Click a color swatch to display the software’s Color Selector.
Inner Color—Sets the color of the densest part of the effect. For a typical fire, this color represents the hottest part of the flame.
Outer Color—Sets the color of the sparsest part of the effect. For a typical fire, this color represents the cooler, dissipating edge of the flame.
The fire effect is colored using a gradient between the inner and outer colors. The dense areas of the effect use the inner color and gradually blend to the outer color near the edges of the effect.
You control the shape, scale, and pattern of flames within the fire effect using controls under Shape.
Two options set the direction and general shape of flames.
Tendril—Creates directional pointed flames with veins along their center. The flames orient along the local Z axis of the fire apparatus. Tendril creates campfire-like flames.
Fireball—Creates round puffy flames.
Stretch—Scales flames along the Z axis of the apparatus. Stretch works best with Tendril flames, but you can use it to give Fireballs an oval shape.
Values less than 1.0 compress flames, making them shorter and thicker.
Values greater than 1.0 stretch flames, making them long and skinny.
You can combine Stretch with non-uniform scaling of the apparatus. Use non-uniform scale to change the boundary of the effect and scale the shape of the flames.
Use the Stretch parameter to scale only the flames inside the apparatus. You can also use Stretch values to reverse the effect that scaling the apparatus had on the flames.
Regularity—Modifies how the flames fill the apparatus. Range=1.0 to 0.0.
A value of 1.0 completely fills the apparatus. The effect fades near the edges of the apparatus, but the overall shape is still very noticeable.
A value of 0.0 produces a very irregular effect that might occasionally reach the boundary of the apparatus, but usually gets trimmed back and is smaller.
You set the size and appearance of flames using parameters under Characteristics. All of these parameters depend on the apparatus size and are interdependent on each other. Changing one parameter affects the behavior of the other three.
Flame Size—Sets the size of individual flames inside the apparatus. The size of the apparatus affects the flame size. A larger apparatus requires a larger flame size. Use a range from 15.0 to 30.0 for the best results.
Large values work best for Fireballs.
Small values work best for Tendrils.
If the flame size is very small, you might need to increase Samples to see individual flames.
Flame Detail—Controls the amount of color change and edge sharpness seen within each flame. Range=0.0 to 10.0.
Low values produce smooth, fuzzy flames and render faster.
High values produce patterned, sharp flames and render slower.
Use higher detail values for large flame sizes. If the detail value is greater than 4, you might need to increase Samples to capture the detail.
Density—Sets the opacity and brightness of the fire effect. The size of the apparatus affects the density. A large apparatus with the same density as a small apparatus appears more opaque and brighter because of its larger size.
Low values make the effect less opaque and use more of the outer color. High values make the effect more opaque and brighten the effect by gradually replacing the inner color with white. The higher the value, the more white the center of the effect is.
Samples—Sets the rate at which the effect is sampled. Higher values produce more accurate results but take longer to render.
You might consider raising the samples value under the following conditions:
Use the parameters in the Motion group to adjust the churn of the flame.
Phase—Controls the rate of change for the fire effect.
Drift—Sets how flames are rendered along the Z axis of the fire apparatus. The value is the amount of rise in units.
For the best fire effects, drift should be a multiple of the height of the fire apparatus.