Game Development and Simulation with Unreal Technology by Alireza Tavakkoli

Author:Alireza Tavakkoli
Language: eng
Format: epub
Publisher: CRC Press
Published: 2015-08-17T14:00:00+00:00

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Game Development and Simulation with Unreal Technology

(a)

(b)

(c)

(d)

FIGURE 6.17: (a) Radial Gradient Exponential Expression Output. (b) One Minus Radial

Exponential Value. (c) The Noise Expression. (d) Multiplying the Noise (by 1-Radial Gradi-

ent).

would like to achieve a more fuzzy look (Figure 6.17(d)).

To achieve this effect, we will use a Noise expression. The output of a regular

noise expression looks like Figure 6.17(c). If we calculate the value of one minus

the output of the Radial Gradient Exponential we get values shown in Fig-

ure 6.17(b). Using 1-Radial Gradient as the bandwidth of the Noise expression

will give us the results we seek (Figure 6.17(d)). The full equation of the emissive

color from network created in Figure 6.14(b) is calculated by:

EMrgb = PColrgb × N (1 − ( RBF(·)))

(6.1)

where EMrgb is the RGB color that the material emits, PColrgb is the RGB color of each particle, RBF(·) is the Radial Gradient Exponential Expression, and N

is the Noise function.

• Material’s Opacity: The opacity channel of the material uses the same calculates

as the emissive color, except the final step. We multiply the output of the noise

expression by the Alpha channel of the Particle Color modules to calculate

opacity (Figure 6.14(b)), see below:

α = PColα × N (1 − ( RBF(·)))

(6.2)

where α is the Opacity channel of the material, PColα is the Alpha value of each

particle color, RBF(·) is the Radial Gradient Exponential Expression, and N is

the Noise function.

INITIAL SPRITE EMITTER PROPERTIES

After setting up and assigning the Sprite’s materials, it is time to set the particle

system up. As we discussed earlier in this chapter, a visual effect is made of one

or more Particle Emitters. Each emitter, in turn, is made of two or more modules.

If you remember, the Required and Spawn modules are mandatory modules

and must be present in each emitter. For most other modules, you can add it as

an initial control module, or an overtime module.

For this particular sprite emitter, we added four modules: three initial modules,

and one lifetime module.

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