2.3 - Black Body Node [Dynamic Parameter Control]

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One very useful feature of the UE4 Material system is the Black Body Material Expression node , which can be found in the Material Editor. Beware, we now have to dive into SCIENCE!

Black-body is a type of radiation that specific types of objects (or bodies) emit at a certain temperature. One of the visible characteristics of this radiation is the spectrum of color of the light that is emitted.

In simple terms, you give the node a real-world temperature in Kelvin, and you get a real-world color corresponding to that temperature. This solves that age-old problem of "what color should this explosion/fire be?" Using the Black Body material node, you can guarantee a realistic color to use on effects. To make the most of the Material Expression, it will help to have an understanding of Black-body radiation.

In this specific example, we use a Dynamic Parameter module within our Particle System. This allows us to create an arbitrarily named parameter that can then be used to drive some aspect of a Material. So we have a custom Dynamic Parameter named Temperature, whose value runs from 4500 to 0 throughout the lifespan of the particle.

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When sent into the Material via a Dynamic Parameter Material Expression, it is used to drive the Temperature input of the BlackBody node. This means that the particle's color is going to reflect what a black body surface would look like as it dropped from 4500 Kelvin down to 0, or in more literal terms, from bright orange down to black.

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