Particles can be made semi-transparent by setting their
Transparency particle property.
Transparency value of 0.0 lets a particle appear fully opaque, while any value in the range 0.0-1.0 renders the particle translucent.
The easiest way to set the
Transparency property is the Compute property modifier.
Simply enter the desired transparency value into the expression field and the Compute property
modifier will assign that value to all particles.
Sometimes you want to make only a subset of the particles semi-transparent. For this, first select the particles,
then apply the Compute property modifier.
Activate its Compute only for selected particles option to restrict the assignment of the
Transparency value to the currently selected particles only. Unselected particles will keep their transparency values (0 by default).
For demonstration purposes, in the example shown on the right, the Compute property
modifier was used to set the
Transparency property according to a simple math formula:
Thus, instead of assigning a uniform transparency value to all particles, each particle’s value is computed
individually from its X position divided by the simulation cell size,
which varies between 0 to 1 from one side of the simulation box to the other.