Glowing/outline effect when particle and object are colliding

Question

How to do a glow/outline of collision effect when particles (objects with same size in a group) are entering other object?

For example when a small box particle is falling into a plane (will fall through), when a box starts touching the plane the place of collision (essentially a square on the plane, around the box particle) is being rendered?

Edit: Adding more info as requested. I don't want to share my real scene, so I mocked a simplified version of it.

Desired effect highlighted with purple colour:

Answer 1

Dynamic Paint and Freestyle

Dynamic Paint. Contrasting particle paint with a mysterious mesh object in the shape of a number moving on the z-axis. The mysterious mesh object is not shown to emphasize the Dynamic Paint process and not mesh movement. No Compositing Nodes. Image Above

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Dynamic paint. Stopping particles with collision plane to show coincident locations.

Dynamic paint with Particle System.

A dynamic paint render. A cyan plane has been colored yellow with fading where the particles have hit the plane. Image above. Please click on image to see a larger version in a different browser window. The images were created by dynamic paint feature and then applied as a texture.

A Blender Render Node system showing a blur node. Please improve and customize.

Dynamic Paint Example. Canvas, Brush, Particle System. Please customize to your tastes. Image above. One panel is pinned to show data from more than one object. Note that using a particles system with dynamic paint may eliminate some options that the OP might find useful in a future version of Blender. The particles above seems to be used for location of the paint effect, disregarding size and shape. The mesh paint effect which is not a particles clearly respect the volume. Particles can be made in meshes by make real. Keep aware of physical forces.

Mysterious Mesh object brush with brush settings for dynamic paint. Not a particle. Image above.

Files created by Dynamic Paint based on particle system typically used as part of a Blender File render. 2 Images above. The yellow blobs show where the particle hit the plane.

• Dynamic paint can detect a contact point / intersection or proximity between

  • Particles and a surface
  • Two objects

and color a surface.

• The Blender compositor can use a [blur node] to create a visual blur because it can recognize different objects by object id. A blur effect can be composed onto the image.

• Freestyle and the compositor. Freestyle topic can be searched here at BSE.

Outlining again.

• You may consider fire/smoke as well.

These three bullet points are high level information. Tutorials exists for these topics on video websites or you may find smaller explanations here at BSE

https://docs.blender.org/manual/en/latest/physics/dynamic_paint/index.html

https://docs.blender.org/manual/en/latest/render/freestyle/index.html?highlight=freestyle

Answer 2

If you set up, say, physics on real instances instead of particles, you may be able to use Dynamic Paint on its own..

Set the Cube(s) up as a Brush.

• It paints white (no alpha) into what will be a black canvas
• From Mesh Volume and Proximity, with the Volume Negated
• And a falloff defined by a color ramp, to give more flexibility with later steps

Set a highly subdivided plane up as a Canvas

• We're painting into vertex colors here. (You could bake the image sequence into a texture instead, if you wanted to work with a less subdivided plane)
• (Drying) and Dissolving are set up to just a couple of frames, so the paint doesn't persist
• We're using the paintmap in this case.. click the '+' to have it set up

Using the paintmap as a mask in a material for the canvas....

• It's picked up by an 'Attribute' node, and used to select between two materials.
• The paintmap is put through a color ramp to give us control over the width/feathering of the rim.

There is some aliasing next to the cube, due to the resolution of the vertex-color layer- So I covered it up by parenting another, slightly larger, inert cube to the smaller one actually doing the painting.

This is the sort of result...

There is an edge-case where a cube-face is exactly parallel to the plane .. then the paint fills the entire square for a frame or two. Haven't found a way round that yet.