I've failed to use a movie as direct texture density input for both particle system and smoke simulation. It seems that this information is still right or simply my setup is wrong somewhere.
So, as a workaround, I used the following modifiers, starting from a subdivided plane:
- Vertex weight edit: this allow to color a vertex group depending on a texture (and this allows to use an animated texture or video)
- Mask: the mask of the previously create vertex group keeps vertices of the mesh depending on the vertex group. We could use the vertex group directly but keeping vertices allows to round the geometry in the next modifier
- Subdivision surface: to round a bit the remaining vertices corners
- Smoke simulation
Vertex weight edit
It is based on the movie texture and adjusted (default weight, add threshold) so that the plane's vertex group are assigned depending on the alpha channel of the texture. The vertex group has to be created before with no vertex assigned to it.
The texture itself is defined as follow:
This first modifier give this result (weight paint mode):
The mask simply uses the previously defined vertex group, so that the plane geometry is restrained to this:
Not really useful, depending on the base subdivisions given to the plane. It rounds a bit the corners of the remaining geometry.
Nearly the default settings, except for the smoke color:
A cube surrounding the previous plane. The resolution has been adjusted using 'smoke high res' and 3 divisions (if you don't do that, the smoke will appear crenelated). The dissolve/life time is set to 5 here.
From the same base setting we could use a particle system, producing itself the smoke. But when there is no geometry (full alpha image), it seems that particles want to appear anyway from the plane origin. So if you want a setting using a PS, place the origin outside of the camera view.
You may have to bake the smoke before usage.
MicroMachine indicated in the comments that it was not an obligation that the flow comes from the circle edges and could be from the whole surface. Nevertheless I've tried to do it using 2 vertex weight edit modifiers: the idea was to create a kind of surrounding mask from the circle. But I failed to do it correctly.