...
Preview > Render Options > Renderer > Maxwell Render
Renderable
Each node can be excluded from the render with this switch. With “Yes” (the default setting) the node will be visible in the preview. Please note that the node's viewport visibility is not taken into consideration by default, and the “Yes” and “No” states work independently from the “Set Selected Visible” and “Set Selected Hidden” options. If you want to use the current state of visibility in the viewport for the node, choose “Same as display”.
...
This parameter is directly related to the “MultiPoint” feature. RealFlow creates the new particles within a certain radius around the particle and here you can specify this radius. This parameter accepts floats and is given in metres [ m m].
Radius
Here you can specify the size of the particles in your Maxwell Render preview. In cases where the particles are hardly visible, appear too small or too big, you can define a new radius here. “Radius” is only available in combination with the “MultiPoint” option. This parameter accepts floats and is given in metres [ m m].