Hi, I figured I’d start contributing, the current smoke engine in blender 2.62 is basically in it’s baby-steps, maybe because we are using a fluid engine instead of one built for fire and smoke erby the physics are incorrect and lack proper controls.
so, I did a scientific study on fire and it’s interactions and gave a few suggestions on an interface to produce fire with ease and total control (which is what artists want)
here is the results of my studies:
Fire and smoke are effected by 6 different sources.
First of all we must understand what is fire and what is smoke, what makes them different?
What is fire:
Fire is not comprised of physical matter but rather plasma, plasma is created by the process of creating heat from a source through the medium of burning materials, the fire itself is not a gas, fluid or solid but rather sin-waves arching between the edges of the combustible materials, these sin-waves are effected by 6 sources:
1: base heat, the base of the fire can be represented as a colour-mat (an image representing hot and cold sections in a topographical format) with certain sections being hotter than others perpendicular to which the sin-waves run, from the apex of these heat sections vertical sin-waves arise and bend the original horizontal sin-waves which represent the base of the fire. These bends create sharp arching points which may move as the base heat colour mat slowly changes over time as the energy or fuel of the fire is spent in certain locations. The bends in the horizontal sin-wave do 2 things; create apexes of the flames (high points) and create new arching points (low points) which can bend the plasmic emissions from the previous arching points.
the center of the fuel zone or center of the fire is usually the hottest point the hotter the point the more energy it contains and the farther it stretches (to a point) the Horizontal sin-waves (HS-wave) as the intensity of the heat drops and then rises again it creates new arching points at the lower points (above the original base). This produces a basic fire shape bend to the plasma
initially the base sin-waves are visibly flat and run in X and Y horizontal directions (can possible be controlled in 2 ways, wave height and number of waves X number of waves Y). The geometry under the waves is the fire, when effected by HS-Waves the fire can be calculated simply by calculating the internal geometry, if a HS-wave cuts out a portion of the plasma base wave that region is no longer filled, HS-waves are always moving upwards this creates initial motion in the flames. when an HS-wave bends the plasma conside the shape it has created around it as a curvesided cone, if there is more than one HS-wave then at the point where the cones meet the fire creates a low point or bend which contains a polarity.
2: heat waves, like above HS-waves are vertically oriented sin-waves that emit from the entire base mat of the fire the rate at which they ripple depends on the intensity of the heat at their emission location, these sin-waves bend the plasma additionally to the basic shape in accordance with it’s outside edge to create extra flickering points and bend the edges of the flames as they go up, the flickering points are created when the heatwave stretches beyond a valid curve of the HS-wave. The stronger the heat; the smaller the ripples in the sin-wave, the lower the heat the larger the ripples in the sin-wave.
3: air pocket temperature, when the plasma’s edge touches a warm or hot pocket of air the edge will bend (side) or curl (tip)towards the warm pocket, when the plasma’s edge comes near a pocket or current of air that is cold it will bend (edge) or curl (tip) away from said pocket if the cold pocket moves through and severs the HS-wave of a section completely it will create a temporary gap between the tip of that arch and it’s base, splitting the fire. The cold and hot pockets of air can be best represented as 3 intersecting heat maps (images), 1X, 1Y and 1Z which can then calculate a air pocket volume.
4: air pocket density, although similar the cold and hot air pockets the interactions of air density are slightly different, a dense volume of air will deter plasma from arching in that direction completely whether it is hot or cold it creates friction on the plasma, a volume of air with very little density is easily permeated by the arching plasma giving very little or no resistance at all. This is best represented as 3 intersecting density maps 1x, 1y and 1z.
5: air currents from moving objects, though the heat/cold air from an object does have some fall-off due to air density, while the hot/warm or cold current coming off a moving object passes by a fire the trajectory of that wind and it’s temperature will have direct effects on the plasma as with air temperature plasma flees from cold and pulls towards warm and hot, however plasma from a fire will always move with a moving air current as if it were a flag in said wind, this wind creates a sin-wave that will effect the whole flame which travels at a trajectory from the center of the hottest base points parallel to the motion of the object, if the object is warm or hot the plasma will arch slightly towards the object breaking the parallel angle, if it is cold the plasma will arch slightly away from the object.
6: Force interaction, plasma cannot permeate electromagnetism at any time, plasma can be bent by the polarities of both electricity (plasma’s fast, strict and stringy cousin which it will arch towards and away from if given the chance based upon the polarity of the electrical source and it’s proximity to the positive and negative arching points of the plasma) and magnetism (from which strangely plasma flees if the magnetic current contains more energy than the sin-wave of the flame)
if there is no magnetism (gravity) or if the fire base is in the shape of a ball with magnetism inside, flames can emit in all directions simultaneously, in order to best simulate a ball of fire the original base sin-waves should already be bent softly into a spherical shape from which HS-waves and heat waves can emit in all directions.
flame colour: flame can be a wide array of colours most distinctively this is based on the colour-heat spectrum; white flame is cold enough to be touched by the human hand without any adverse effects, white flame is only present where blue flame occurs because blue flame is absorbing all the energy and fuel leaving a hollow white plasma inside, blue flame is the hottest possible flame. Green flames happen when chemicals from plastics or certain gasses are burnt the reason being is the toxic chemical is extremely reactive to heat and will flee from it as fast as possible, this energizes the plasma as it travels trough it creating a non-polarity based colour.
So white is the lowest heat; white<yellow<orange<red<violet<purple<blue
this is plasma’s natural colour spectrum. Though through a custom colour spectrum other colours may be achievable. (I suggest displaying a default color spectrum and allow the user to edit each increment of this spectrum via colorband.)
Plasma never mixes colours, each colour is distinctly separated.
Flame energy fall’s off becoming weaker as it travels, this causes a change in colour outside of a certain distance away from the fuel, based of coarse on the temperature and density of the air and the amount of original energy, the colours are based on the colour spectrum of the fire as the fire’s energy falls off the colour changes will happen in closer colour-bands. After the white and sometimes paper-thin colour-band the plasma ceases to hold enough energy to emit light but creates a light-bending and waste filled set of heat waves called smoke. But we will get into that in greater detail later.
A sun: a sun is not just a ball of plasma, but rather a ball of burning gasses, the gasses used and their quantity determine the colour of the plasma, it is actually mainly the quantity that determines colour of a star because more quantity = more gravity= more compression = faster burning= more energy.
The smaller a star the weaker the flames such as the white and red dwarfs a red dwarf usually contains black, used non-burnable gas that gives of a red glow and a few red flames, a white dwarf contains slightly less quantity of gasses than a yellow star, though stars also contain billions of nuclear explosions which in fact actually spawn the plasma and give off flares of flame off the main mass.
On the surface of the sun this can be represented as a series of small cloudy eruptions, as these eruptions conflict flaming gaseous and possibly forked strands are emitted in flares from lines in between the many explosions, theses flares may bend or wrap around the star’s gravitational pull in any direction before they exit it’s domain being effected (bent and expanded) by other explosions as they travel.
Fire can easily be conformed to any shape by manner of simple deflection by a non-fuel material.
Fire can also be bent by fuel materials as it wraps around their geometry violently consuming their solid energies.