You can view the shape types in Textured display mode except for the Noise, Turbulence, and Fractal shape patterns.
When you’re defining the look of a particle type, setting its shape plays a significant role. The Shape shader provides a plethora of 2D shapes from which you can choose, including setting the shape’s position within the particle radius and setting its transparency falloff.
To connect the Shape shader
• Connect the Shape shader to the Color input of the Billboard shader.
By default, the Shape shader is already attached to the Billboard shader when you create a particle cloud: these two complement each other nicely because they’re both useful for 2D effects. The Billboard shader creates the 2D surface while the Shape shader provides the actual shape definition and look.
In the Shape shader’s property editor, you can choose from these shape types on the Shape page:
• Step uses a ratio (its Width) of the particle size to set the shape in a single step.
• Sine creates a particle with a number of rings that are equally spaced from one another. The Sine’s Scale controls specify the number of rings used.
• Star creates a particle with a star-like configuration. You can specify the number of branches used (default is 4).
• Beam gives the particle a long beam shape with a bright center surrounded by a glow effect. You can specify the width of the beam.
• Symmetry creates a symmetrical particle shape whose width you can set.
• Noise can be used to create a variety of chaotic effects. Based on one basic pattern, you can modify the spacing and the level of detail using its Time and Size controls.
Time lets you control the animation of the noise over time by connecting a Particle Scalar shader and setting it to Global Time (or particle age).
• Turbulence creates irregular cloud-like patterns. You can control its size and high and low frequency patterns. This is often useful for creating smoke and fog effects. As with the Noise shape, you can set the Time to control the animation of the turbulence.
• Fractal creates iterative fractal-based patterns. You can set its size, granularity, weight of iterations, and number of octaves. As with the Noise shape, you can set the Time to control the animation of the fractal pattern.
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You can view the shape types in Textured display mode except for the Noise, Turbulence, and Fractal shape patterns. |
Setting the Shape’s Falloff (Transparency)
The falloff for the shape is the rate at which the transparency around each particle decays. For any shape that you select, you can set the type of falloff (transparency), as well as offset it from the particle pattern center. The range defines where you want the falloff to start and end, in relation to the particle pattern center that you specify.
To set the type of falloff
• Select a calculation method from the Type list on the Falloff page in the Shape shader’s property editor.
The type of falloff is the calculation method used to determine the falloff’s general shape. You can select from square, cubic, linear, smooth, Gaussian (bell-shaped), user-defined, or none.
- If you select User-defined, you can set its Exponent value, which controls the transparency falloff rate. Values less than 1 give a steep falloff from the center. Higher values give a more gradual falloff.
- If you select Gaussian (bell curve-shaped falloff) as the type, you can control the Rate of falloff. Higher values give a more rapid falloff.
To set the falloff pattern center
• Enter a value for the Pattern Center X and/or Y text boxes on the Falloff page in the Shape shader’s property editor.
These values determine the center point for the falloff pattern in X and/or Y according to the particle’s center. This lets you offset the falloff from the particle’s center.
To modulate the RGB/Alpha values
• Select the Modulation RGB and/or Alpha on the Falloff page in the Shape shader’s property editor.
This multiplies the RGB and/or alpha components of the base particle color by the falloff value at the intersection point.
• Select Inverted for the RGB and/or Alpha options to invert the shape value when multiplying the RGB/Alpha components.
To set the range of falloff
• Enter values in the Range Start and End text boxes on the Falloff page in the Shape shader’s property editor.
This is the distance from the pattern center at which the falloff value goes from 0 to 1. The falloff value is interpolated between the Start and End values using the Type of falloff you have selected.
Autodesk Softimage v.7.5