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So I've been in animation a long time but am new'ish to Blender.

Two things I cannot seem to do are fairly simple to code:

Firstly, I need particles to emit particles when they hit a surface.

Secondly, If I have a particle system, the particles must have a direction so how do you get this to drive instanced object direction?

I am massively simplifying these questions, but thats what they need. I have had several needs for the second one, say arrows showing the flow of fluid / gas / electrons, and the first is just where I want a sprite flash to appear where a glowing line hits a wall - I'm copying a 1982 hand drawn animation, surely we can do these basic things in 2020?! :o)

Thanks in advance

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  • $\begingroup$ Please show your current work in a Blender screen capture. You can have the initial particle direction come from the surface normal. Then the speed is adjusted in the particles panel. I am addressing the second question first because it is simpler. $\endgroup$ – atomicbezierslinger Feb 14 at 16:51
  • $\begingroup$ At this site typically the question should be as small as possible and not multiple or tutorial questions. It seems you need a tutorial. In the past, this site is not about tutorials. You can find tutorials about the basic setting of particles in video tutorials on a famous web site that rhymes with noonoob. $\endgroup$ – atomicbezierslinger Feb 14 at 16:55
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    $\begingroup$ Hi. Please only ask one question at a time. You are welcome to ask multiple questions, but as separate posts. $\endgroup$ – Ray Mairlot Feb 14 at 18:41
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First question: it can be done in Blender in versions before 2.5, for example in now very old 2.49b. The file locations for download is here [1]. The mechanism you are looking for is called 'reactor particles'. It was unfortunately not re-implemented in 2.5+ series.

In Blender versions from 2.5 to 2.83 you can not do the effect of spawning particle with another particle easily. Particle system in Blender in it's current form is on it's end-of-life state, and there will be no updated to it, because it is planned to replace it by Particle Nodes. Example [2,3]. Some workaround for this poor situation is to introduce Animation Nodes [4] and find your way thorough them. This requires a lot of learning and is considered to be advanced stuff, so no point to explain it here. You really need a tutorial.

Second question: animation of flow can with direction can be done kind of easy using small custom object arrows and particle flow controllers like 'curve field' (curve guide) or 'keyed' particles [6]. This however requires also a tutorial, for example this (first from google): [5]

  1. https://download.blender.org/release/Blender2.49b/
  2. https://www.youtube.com/watch?v=A05UghlpVPs
  3. https://www.youtube.com/watch?v=2tKpHuq9qEk
  4. https://www.youtube.com/watch?v=8pvX2_ZH1l0
  5. https://www.youtube.com/watch?v=PYHOV3bVIG0
  6. https://docs.blender.org/manual/en/latest/physics/particles/emitter/physics/keyed.html
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  • $\begingroup$ Hi, thanks for the volumintous reply! I used to program so I know these things do not need to be difficult to use. maybe there should be a basic but well thought out system for particles and the ability to switch to nodes as, frankly, its nice to have that control but in other packages users are left just copying a tutorial an with the clock ticking its time consuming, clunky and unfriendly. SoftImage went down this route with ICE, LightWave with it's nodes, C4D with it's complex system but Houdini, ah, perfection! $\endgroup$ – Prince Westerburg Feb 14 at 23:21
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For the first one you can use the dynamic paint, make the object which will collide as brush and which it will hit as canvas(can be found in physics tab). Then put the output to weight paint and apply the output weight paint to object with canvas applied(subdivide the mesh first). Then you can make particle system on canvas and use weight paint for editing particles(you will have to increase length of emission for long animations).
For the second one you may use force such as wind force in order to to drive them in direction you want.

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