Paint/Erase: controls which paint mode to enable in the viewport.
Clear all painted particles: clears all previously-painted particles from the operator’s internal cache.
Default radius: the default radius of the paint/erase brush.
Stroke spacing %: the distance between each group of particles painted during a single stroke.
Update flow continuously: when selected, the flow will continuously reset while strokes are painted, allowing the simulation to update on the fly.
Update flow on mouse button up: when selected, the flow will only reset once the stroke’s mouse press has ended, updating the simulation only after the stroke is finished.
Birth particles at paint time: painted particles will be born at the frame the time slider is set to when their stroke is complete.
Birth particles at specified time: painted particles will be born at the specified time, ignoring the location of the time slider.
Birth particles at all times: painted particles will be born at all frames in the timeline.
“Birth particles at all times” makes it easy to use the Birth Paint operator with a history-independent flow. Using another mode with a history-independent flow will cause particles to disappear at unspecified/unpainted frames.
Offset: the distance from the scatter surface a painted particle will be offset.
Alignment X/Y/Z: controls which local transform axis the particle will be aligned to.
Surface alignment %: controls the interpolation between world alignment and surface alignment for particles. Higher values mean particle orientations will be interpolated between their scatter surface, rather than the world.
Random rotation around alignment axis: particles will be rotated a random amount around the specified alignment axis.
Paint particles in WORLD space: particles will be painted in world space, ignoring any post-paint changes made to their scatter surface.
Paint particles in OBJECT space: particles will be painted in object space, remaining linked to the transform of their scatter surface even after post-paint transform modifications.
Paint particles in SURFACE space: particles will be painted in surface space, remaining linked to the geometry of their scatter surface even after post-paint surface modifications.
Changes affect particle scale: when enabled, transform/surface changes will affect particle scale. For example, in SURFACE mode, if the area of a face on which particles are painted is doubled in size, the particles themselves will double in size.
Object and surface space modes allow you to make changes to your scatter surfaces that will affect where particles are born after they are painted. For example, if you paint grass particles on hill geometry in SURFACE space and then make changes to the hill geometry, when the simulation is reset the grass particles will move to match the new hill changes. Note: SURFACE mode requires consistent topology. Changes to vertex/face counts will prevent particles from remaining linked to the surface in subsequent flow updates.
Default density: the default number of particles the paint brush will create, each time particles are painted during a stroke.
Density falloff: a curve which defines how particle density will falloff towards the edge of the brush.
Default scale: the default scale of particles the paintbrush will create, each time particles are painted during a stroke.
Scale falloff: a curve which defines how particle scale will falloff towards the edge of the brush.
Default opacity: the default opacity of the erase brush. Is the probability that any single particle under the brush will be erased, each time particles are erased during a stroke.
Opacity falloff: a curve which defines how particle erase opacity will falloff towards the edge of the brush.
Scatter on ALL surfaces: all surfaces in the scene will be treated as potential scatter surfaces.
Scatter on SELECTED surfaces: only selected surfaces in the scene will be treated as potential scatter surfaces.
Scatter on LISTED surfaces: only surfaces in the surface object list will be treated as potential scatter surfaces.
Spread across ALL surfaces: when enabled, any surfaces under the brush may receive particles, depending on whether a particle from the brush is overtop it during a stroke.
Spread across HIT surface: when enabled, only the surface directly under the center of the brush will receive particles during a stroke.
Filter by face selection: when enabled, only selected faces on surfaces will receive particles.
Filter by material ID: when enabled, only faces with specified material IDs will receive particles.
Filter by normals: when enabled, only faces will matching normals will receive particles.
Scatter NO shapes: particles will not be assigned shape meshes.
Scatter RANDOM shapes in list: when enabled, particles will be assigned a shape mesh from any random object in the particle shapes list.
Scatter SELECTED shapes in list: when enabled, particles will be assigned a shape mesh from a random object from the set of selected objects in the particle shapes list.