How can I use the result of Vertex Weight Mix Modifier as Vertex Group input of Particle System?

Question

I have a Vertex Weight Mix Modifier and a particle System. I want to control the density of the particles with the result of the Vertex Weight Mix. Is this possible?

Answer 1

Yes, it is possible:

A few important notes:

• in the Particle System > Emission > Source section the checkbox [X] Use Modifier Stack must be checked
• the Vertex Weight Mix modifier must be above the Particle Settings modifier
• the group for the mixed result must be defined as Particle Settings > Vertex Groups > Density and as Vertex Group A in the Vertex Weight Mix modifier settings
• you need to change the default values of the Vertex Weight Mix modifier to proper values, especially the Vertex Set and Mix Mode
• you can see the modified weights (Vertex Group A) in Weight Paint mode, and with help of the Vertex Group Weights overlay in Edit mode (make sure the modifier is enabled for Edit mode; check the icons right next to its name).

The faces of the cube in this example have been inset (I) and each of the inner faces has been assigned to a vertex group (Modified Top, Bottom, Left, etc). The modifier modifies the group that is specified as Vertex Group A (=Modified Top) depending on the other settings:

• in the 1st screenshot the modifier adds the verts of the bottom group to the top group
• in the 2nd screenshot it replaces the top group with the left one