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These material graph samples demonstrate how to implement simulation of black-body radiation for physically accurate emissive materials. Two material graphs are included.
The blackbody_box material showcases the change of color based on the temperature on a box.
The horizontal component of UV coordinates taken via the x port adapter from the Vertex UV 0 node is multiplied by the Temperature value (in Kelvin) provided by the Slider parameter node (enabling you to adjust the maximum temperature in the Parameters panel). Thus the changing temperature values are mapped horizontally on the box faces.
Then, we simply pass the temperature to the Blackbody node to get the corresponding color.
Additionally, the source temperature in the [0; 1000] range is remapped (the Rerange node) to the [0; 1] range and multiplied by the U texture coordinate and the color is multiplied by the saturated result preventing cold parts from being red.
Finally, the resulting sRGB color is to be converted to RGB values via the SRGB Inverse node and passed to the material's Emissive port.
Albedo and Specular values are specified directly using the Float nodes.
The blackbody_rifle material graph contains a ready-to-use implementation of blackbody-based emission of hot parts of an object.
Temperature-based colorization is applied the same way as in the previous sample, but this time vertex positions in the object space are used to define the hot parts. The y component of the Vertex Position node is adjusted via the Contrast node to make a sharper transition along the Y axis.
And the resulting mask multiplied by the Temperature parameter is used in the familiar network implementing the blackbody emission.
Albedo, Metalness and Roughness values are obtained from the corresponding textures via the Sample Texture nodes and multiplied by the corresponding intensity parameters. The Specular value is specified directly using the Float nodes.