Hi,

I have a basic pyro simulation (a variation of fireball setup from shelf). I have the following questions regarding heat and temperature fields:

1- Although no fuel is injected in the grid, temperature is increasing? If there is no fuel in the grid, why temperature keeps increasing? I set cooling rate to 1.0 and I still see temperature going up and down (according to the documentation 1.0 should remove all temperature!)



2- What is the difference between heat and temperature? I know Mantra renders “heat” as fire, but what makes it different? Why not just say and temperature > 10 will be rendered as fire or black body?

Thanks,

Okay, first part is answered, i.e. I still have fuel in the system due to fuel efficiency …
second question is still not answered …

Heat and Temperature have different uses in the sim, so can contain different data, which may be useful at render time to combine them in different ways. Heat comes directly from the burn field so is more directly shaped by the flames. Temperature directly controls the simulation through buoyancy (or as a control field,) and is often modified by the artist to control behavior. This leads it to sometimes be less ideal for use directly in rendering, especially if random noise (disturbance) is added to temperature, then the flames will render everywhere if it is the sole emission control. Due to its noisier content and wider range, temperature is typically used to control black body emission, with the cleaner heat field acting as an intensity scale. Keep in mind that the shaders and solvers are completely editable, some artists discard them in favor of their own workflow, so this convention is by no means set in stone.

Okay, so to make sure I understand you correctly:

> Temperature is controlled by artist (i.e. an artist can paint temperature profile in the grid), also, Temperature could be adjusted by noise (disturbance), finally it's part of the physical simulation parameters (i.e. density moves from high to low temperature).

> Heat is where there is enough fuel and temperature is high enough (another way to say it, Heat is the intersection of fuel and temperature fields). It could be that there is high temperature but no fuel, and hence no Heat or burn occurs, and that's why high temperature is not enough to detect “burn”

Thank you