Original Question (Edit below):

enter image description here

I want to make a "fluid pressure" representation. That image was my "first" try, but I can't rotate or move the matrix. Why do I want to move it?

I want a "room" made of "pressure representation" walls. So, If I can copy the matrix, I could rotate it. I could, even, animate as a child of an object.

But the real effect I want is in this tutorial: https://www.youtube.com/watch?v=Vxc4P0YI2rI&t=493s

Because in this way, I could have "pressure arrows" for all the volume, no matter the shape/surface form.

But instead the instanced/matrix/particles objects rotating...

  • Scaling (with a minium visible size to something larger but no huge)
  • Rotating (45º because the effector or direction effector).
  • Changing color (Blue neutral, Red affected by effector.
  • Along surface (as the tutorial shows for the "scales").

Here are my nodes and blendfile:

PS: I made that one blendfile, but I took the next blendfile from here:

enter image description here https://drive.google.com/file/d/0ByYo18t3qZRLajNDejF6eFVnYmM/view

and tried to split and understand what is happening in order to achieve the effect I want.

EDIT because it's not solved yet

Thanks to Omar Ahmad, now I have a clean node way to scale the "pressure arrows" from a empty with a "sphereic falloff" and I mix that idea with a "vertical falloff".

The color works only in "vertical falloff" but the rotation is child of normals... would be to difficult affect the local rotation of the arrows to the same "world side"? I have upper arrows rotating correctly, but below arrows rotating in the opposite direction and middle arrows nothing at all. With the inner faces of a sphere is samething.

enter image description here enter image description here

  • $\begingroup$ Where exactly are you stuck in your implementation. It seems you have already achieved a great deal of what you wanted to achieve. In other words, what exactly is your question? $\endgroup$
    – Omar Emara
    Commented Apr 5, 2018 at 19:50
  • 1
    $\begingroup$ Hi, Omar I edited my post so I can share images, links and a blendfile easily. In that last new Blendfile is another attempt to get what I want. I want to put arrows pointing the inner faces of a volume (a room, a bottle, a box, etc...) and animate the "pressure changes", represented as red, bigger and rotated arrows, while the "neutral pressure", the one in "0 state)/not affected by waves, are blue, straight agains the internal faces of the volume/container, and of a regular size. $\endgroup$
    – Jota
    Commented Apr 5, 2018 at 21:12
  • 1
    $\begingroup$ maybe something like this blender.stackexchange.com/questions/48519/… but also changing color and rotation. While ALL objects rotate a little $\endgroup$
    – Jota
    Commented Apr 5, 2018 at 21:15

1 Answer 1


To put arrows pointing along the normals of the vertices of a room, you can sample the vertices normals, convert them to Eulers through the Direction To Rotation Node and use that euler along with the vertices locations ro compose a list of matrices representing the transformations of arrows. Then we you can offset those matrices just as you did implementing the variable scale and rotation, and the color can be set as a vertex color just as you did (Making sure Deep Copy is enabled in the instancer node):

Node Tree


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