Smoke opacity diagram behavior

[olika]

Hey guys hope you can help me understanding a thing once again,

i`m playing around with the smoke opacity diagram in the volume settings of the emitter.
Situation is, i`m almost having the same setup as created in the ground dust horses tutorial (thats well made great job btw!!).
Now i would like to have the first frames of when the smoke gets emitted to be transparent (just because i`m using a distance map with particles and the placement isn`t so accurate so i want to cover that a bit)
but i`m confused playing around with diagram, i already read something bout a-peak curve etc. but somehow i don`t understand it completly also when turned on with standard settings why it looks so awfully different than just the smoke channel?
Anybody can give me some tips on that one? thanks in advance!

[Gosho.Genchev]

Hey there, olika , I'll try to give you a somewhat structured answer. So:

1. The reason for the difference between the "Based on: Simple Smoke" and the "Based on: Smoke" options is most likely due to the fact that the diagram for the Smoke option starts from 0.1. If you set the first point to X:0 Y:0 , your result should be pretty much identical to the Smoke option.



2. The diagram for the Smoke option works as a remapping tool. The input for the diagram is the values of the chosen channel, and the output depends on the points you place on the curve. Please take a look at the picture.




3.

Now i would like to have the first frames of when the smoke gets emitted to be transparent (just because i`m using a distance map with particles and the placement isn`t so accurate so i want to cover that a bit)

A very cool way to go about doing this is to use a VRay Distance texture to modulate the Smoke Opacity. I'll upload an example scene for you.
What you need to do is to simply enable the Modulate option in the Smoke Opacity tab and give a VrayDistanceTex to the Texture slot. The map will work as a multiplier for the Opacity diagram so you can use them both together. The Distance parameter on the texture will affect the radius around the objects in the VRayDistanceTex Objects list where the texture will evaluate from ~Near color~ to ~Far Color~.
Of course, you can invert the far and near colors if your setup requires it.






The file with a single frame of the cache files is here: https://drive.google.com/file/d/1prH...


Cheers !

[olika]

Hi Gosho!
thank you so much for your well explained answer,
although it seems to me i can`t get it to work with particles, could that be? pls see screenshot

[Gosho.Genchev]

Hm, looking at your setup, maybe a better option would be to use the Time Base option for the emission on the source.

https://docs.chaosgroup.com/display/...ource-Emission

Now i would like to have the first frames of when the smoke gets emitted to be transparent (just because i`m using a distance map with particles and the placement isn`t so accurate so i want to cover that a bit)

Maybe instead of trying to make the smoke transparent in the first few frames you can simply not emit for the first couple of frames of the life of the particle. Do you think that would work for you?

Parameters of the source will be animated based on the age of the particle. This way, values at timeline frame 0 will apply to each particle at the moment of its birth, and e.g. values at frame 10 will apply to the particle 10 frames after it was born.

You need to set the Time Base to Particle Age, go to the first frame, and set the Outgoing Velocity for the source to 0. Then, if you want EACH PARTICLE to start emitting 10 frames after it was born, set a keyframe for the Outgoing Velocity of the Source at frame 10.
The way this works is a bit hard to get your head around at first so I'll copy the important bit from the docs

the Absolute mode will change the discharge of all particles together, while Particle Age will allow each particle to have its own copy of the animation.

Hope this helps. Cheers!

[olika]

Hi Gosho.Genchev ,
sorry for my late reply, that projject kept me crazy busy, super happy i managed it and learned a lot again, thanks for your support!
Here is the official clip:
https://www.redbull.com/nl-nl/track-...18-greg-atkins
and here a little breakdown of the project:
https://vimeo.com/281939493