this tutorial shows how you can create the infection effect above in blender simulation nodes
video tutorial: https://youtu.be/sgsvmXPW4Kw
create a vertex group of vertices where you want the effect to start, and name the group infection_start
you can use this to create a mask that grows every frame using simulation zone, this is going to be the base of the whole project onto which we shall create different layers of effects.
there are 4 main parts of the effects
the mask generation
this stage turns the vertex group into a mask, that can be used by the other effects and in the shader editor.
the mask is generated by blurring the vertex group attribute, and adding it back to it self as a stored attribute in the simulation zone, giving the effect of the mask growing every frame.
Face swelling effect
for the face swelling, when you add the normal node directly into the offset of the set position note, the mesh will swell in every angle, if you use the mask from the simulation you can use it to determine what parts of the mesh swells, i added extra nodes like the float and blur node to make the swelling smooth.
since the mask is animated, the swelling will also animate.
this is built ontop of the swelling, distribute some points onto the swelling face, and instance a boil mesh onto them using the distribute points on face node, and the instance on point node.
if you plug the mask from the simulation into the scale, the instances will scale as the mask grows but they wont stop, to make them stop, i add a map range and set the max value to a noise to have some random scale so that each boil has a random scale.
the veins animation is also built on top of the swelling effect, using the shortest path to generate curves that are turned into veins.
the shortest path nodes generates a path of curves from a starting point to any other point on the mesh.
the start point in this case would be the vertex positions of the vertex group we created, then the end position is a random vertices on the mesh selected with the random value node.
to animate the growth effect, use the trim curve and use the mask animation from the simulation inverted with a ramp or float curve node plugged into the trim curve
now just join the effects