I watched this blender guru tutorial on Making Fire. Around 34:00 he starts explaining how to use a particle system to create "fireflies". The result is something like this

enter image description here

Now I have this idea to create a "burning earth". For this I have a UV sphere inside the earth as an emitter of fire and smoke. And the smoke domain is placed like this.

enter image description here

This results in an image like this.

enter image description here

So far so good. But when I add a particle system to my "emitter sphere" the whole sphere is emitting fireflies and I want only fireflies around my fire. I thought to solve that by creating a circle under the fire and add a particle system to that circle. But how to get this working like that the circle emits fireflies that are driven upwards by the smoke domain ??

I guess (with hindsight) this question is a possible duplicate for this question How can I control where smoke and fire are emitted from? but I think because my question is specific for the Particle System it adds new knowledge to Blender SE

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    $\begingroup$ possible duplicate: blender.stackexchange.com/questions/23226/… $\endgroup$ – user1853 Mar 1 '16 at 11:47
  • $\begingroup$ @cegaton yes, with hindsight you are probably right. But I did not know about vertex groups and my question was related to the particle system. $\endgroup$ – Old Man Mar 1 '16 at 12:05
  • $\begingroup$ that's why I wrote "Possible" :) $\endgroup$ – user1853 Mar 1 '16 at 12:10

You should either define a vertex group on your sphere and change the particle settings (also for your fire and smoke) to limit emission to that vertex group or, seeing that you seem to be using this sphere for nothing else, simply delete the parts of the mesh that should not emit particles or smoke.

Quick explanation of vertex group approach:

  • Select your mesh,
  • go into Edit mode,
  • then select the vertices/faces that you want to emit particles/smoke,
  • then go to the object data tab and create a new vertex group by clicking the "+"-button in that area. You should give the group a meaningful name.
  • Then click the "Assign"-button beneath the list of vertex groups while your new group is selected and the selected vertices will be assigned to that group with a weight of 1.0.
  • Next, go to the particle settings under Vertex Groups and select your new group for the Density setting.
  • For smoke, look at the Smoke Flow Advanced section of the emitter object's smoke settings. You can select the vertex group there.
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    $\begingroup$ could you tell me more about your solution with vertex groups ? This is new to me $\endgroup$ – Old Man Mar 1 '16 at 10:42
  • $\begingroup$ OK, done. ;) See updated answer. $\endgroup$ – Oliver Giesen Mar 1 '16 at 11:21

Weight paint the sphere where you want the particles to emit.

  • $\begingroup$ could you explain a little more, this is very new to me. I guess your suggestion works like a mask in Photoshop ? Or maybe suggest a good tutorial that explains weight painting ? $\endgroup$ – Old Man Mar 1 '16 at 10:32
  • $\begingroup$ Yes. You can define a vertex group (select vertices and add them to group in the mesh panel) and use it in the Particle System. $\endgroup$ – AdamTM Mar 1 '16 at 10:38
  • $\begingroup$ ok, I have defined the Group and assigned the vertices to that Group. How can I now connect that to the particle system ? $\endgroup$ – Old Man Mar 1 '16 at 10:54
  • $\begingroup$ I see Vertex Groups under Properties>Particlesystem. But what fields to use ? $\endgroup$ – Old Man Mar 1 '16 at 11:01
  • $\begingroup$ thanks, this is a good solution. I now understand I can use that vertex group also for my fire emitter, cool !! $\endgroup$ – Old Man Mar 1 '16 at 11:14

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