The Select operator allows you to manually select particles in the viewport for further processing.
Send out selected: when this mode is enabled, particle selections will be processed during the simulation, and selected particles will be output from the operator. Selections made in this mode will affect the integrity of the simulation. Changing the selection will require the simulation to be reset for consistent results.
Cull selected: when this mode is enabled, particle selections will only affect the visibility of particles during display/rendering. Selections made in this mode will not affect the integrity of the simulation and do not require the simulation to be reset for consistent results.
Select from entire flow: all particles in the flow will be available for selections, even if the particles are not present in the Select operator’s event.
Select from this event only: only particles in the event of the operator will be available for selections.
If “select from entire flow” is enabled, particles may be selected from other events (even though only particles within the operator’s event will be sent or culled). The reason for allowing particles from other events to be selected is simply because the alternative may be counter-intuitive in some situations. For example, when in “send out” mode with “select from this event only” enabled, if your flow is set to auto-reset and you select some particles, they will be immediately output from the operator and thus become un-selectable (because they are no longer in the event). The logistics of this behavior may be consistent but it can be jarring to no longer have selection access to particles you just selected simply because you selected them. That is why “select from entire flow” was added as the default selection mode.
Select particles: activating this checkbutton enabled particle selection mode. Once activated, particles can be selected in the viewport with a mouse.
Clear selection: when pressed, the internal list of selected particles will be cleared.
Regular selection menu items accessible from 3ds Max’s Edit menu (invert selection, clear selection, select all) will work in particle selection mode, as well as regular undo/redo commands.
Selected/Unselected display modes: controls how selected/unselected particles will be displayed in the viewport.
Always display selection: selected particles will be marked in the viewport even when selection mode is not activated.
Disable non-geo display while selecting: when enabled, Display operators set to non-geo (point) display will be disabled while selection mode is activated. This helps to prevent Display operators from obscuring particles displayed by selection mode itself.