This is my collection of flame particle expressions. I generally clone it to my flame user folder and update as I make changes.
The commonly referenced list is below:
transparency = lifetimeI
transparency = (1-lifetimeI)
transparency = sin(lifetimeI)
transparency =sin(lifetimeI*1.5)
transparency = cos(lifetimeI*1.5)
transparency = sin(lifetimeI*3.14)
transparency = power * ( sin( lifetimeI * 3.14 ) )
This is better than transparency = lifetimeI because with the previous formula you would have particles 'pop' on and then fade. I had some popping occur when I was trying to make smoke from a chimney, but it gave this interesting puffing effect.
transparency = transparency / sin(lifetimeI) * power
fade down in the middle of the particles life, with power control (power is between 0 and 1) (control with power)
transparency = -0.05(pow(tan((lifetimeI-0.5)/0.37, 2)) +1
Produces a very steep up flat top , very steep down curve, no explict control.
transparency = -(magnitude*lifetimeI) (lifetimeI - 1)
transparency = 1 - smoothstep(100,400, length(pos-(100,0,500))))
In this case only near coordinates 100,0,500 - the old light default location, 100 and 400 define the distances close and far - that limit the transparency. I used this when I wanted rain to light up around a street light, - unlike a matte it works in 3 space, like a ball - when the rain enters the ball it lights up- very nice
transparency=pow(lifetimeI,magnitude)
transparency = sin(lifetimeI + turbulence(pos,1))
A great function that acts more naturally in fading off particles
transparency = ( ((1-lifetimeI)<power)*smoothstep(0,1,(1-lifetimeI)/power)) + (((1-lifetimeI)>=power)*smoothstep(0,1,lifetimeI/(1-damping)) )
This amazing function allows you to move the mid point of the fadeup/off and effect the out (via damping) try damping = 25% and power =0.5
transparency = (((1-lifetimeI)<power)*(1-lifetimeI)/power) + (((1-lifetimeI)>=power)*lifetimeI/(1-damping))
fade up to frame set by power -fade down from frame set by damping (don't use damping values lower than power) -change damping to power if you want it to fade up and down immediately. Try power=0.25, damping=75
transparency = (lifetimeI>0.5)*lifetimeI + (lifetimeI<=0.5)*0.5
(lifetimeI>0.5) returns 1 when lifetimeI is greater than 0.5 and zero when lifetimeI is less than 0.5
and likewise (lifetimeI<=0.5) returns 1 when lifetimeI is less than or equal to 0.5 and zero when lifetimeI is greater than 0.5 thus multiplying the then and else functions by their respective conditional expressions and adding them together results in transparency fading down to 0.5 until halfway through the particles life and then remaining at 0.5 till the end....
rgb = (red*lifetimeI, sin(lifetimeI), 25)
Colors shift through the range during their life
rgb=(red*lifetimeI, green*pow(lifetimeI,2), 0)
In Surface/Geometry, keep the diffuse/specular/ambient colours as default (white/white/black). The first frame of the particles will be white, but then jumps to yellow because of the above expression. The green channel drops faster than the red channel, producing orange before red and then black. (tip: great for fire)
rgb=(red*lifetimeI, green*pow(lifetimeI,2),blue*pow(lifetimeI,magnitude))
If you want white to cycle to yellow, you could add an expression in the blue channel that drops very quickly . try magnitude =10
rgb = ((1,0,0)-(0,0,1))*smoothstep(0,1,lifetimeI))+(0,0,1)
This will make the color go from red-purple,
speed = speed + cross ((power, power, power), noise3(pos))
Changing the power and speed affect the turbulence...try power=3.0
speed = speed + cross ((power, power, power), noise3(pos)) * magnitude
Changing the power, speed and magnitude all affect the turbulence... * note:In the above two examples, you can achieve some very interesting effects by keyframing the power, speed or magnitude channels. For instance, start out with very little turbulence and then ramp up into something really chaotic!
speed = speed + cross( (power,power,power), turbulence3(pos,1)
Same as above but using turbulence rather than the more 'random' noise function. note it is turbulence3 as we need the vector version.
speed=(speed+cross(power*((1-lifetimeI)/2), power *((1-lifetimeI)/2), power*((1-lifetimeI)/2)), turbulance3(pos,1)))
Turbulence 1: Speed is defined as speed = speed + another speed vector ,.. plus it scales down the final vector by lifetime.
speed=(speed+cross((power*(1-(lifetimeI/2)), power*(1-(lifetimeI/2)), power*(1-(lifetimeI/2))), turbulence3(pos,1)))/ (magnitude,magnitude,magnitude)
Turbulence 2: As the speed is defined as speed = speed + another speed vector ,.. we also need to scale down the final vector. So you need to divide everything by say (magnitude,magnitude,magnitude)
speed=speed*0.95+turbulence3(pos*0.01,1)
When rendering out thisone with let's say a full light with 180 spread on it as the generator what you will see are the obvious flows and eddies that the particles move through (use lines to see this, only one manipulator for the function).
speed=speed*0.95+turbulence3((pos+(0,0,frame*20))* 0.01,1)
In this formula you begin to see the flows and eddies and then they are suddenly disrupted. In the first formula the variables are 0.95 and 0.01. In the second the 20 is also a variable. A lower number should make the swirls evolve at a different rate. The 0.01 value in both lines effects the apparent lattice scale. A smaller number makes for a bigger lattice, creating bigger/looser swirls. The range for this will be 0.1-0.001.
speed = speed + (sin(lifetimeI/2 + 3*turbulence(pos,1)), sin(lifetimeI/2 + 3*turbulence(pos,1)), sin(lifetimeI/2 + 3*turbulence(pos,1)) )