4. Add Ground Contact¶

Add ground collision and compare bounce, friction and particle contact size.

Use the fountain scene¶

Open lesson 3 and save as 04-collision.blend. Keep its Emitter and three effects.

Add the ground¶

1. Add a cube named Ground, Dimensions (12, 12, 0.3), Location (0, 0, -0.15). Its top surface is Z 0.
2. Apply object scale.
3. In Effects, use Add Effect... > Collision and assign Ground as its collider object.
4. Set Bounciness 0.2, Friction 0.5, and Apply to: All.
5. Place Collision after Drag in evaluation order, at the top of the visible Lists stack.
6. Replay frames 1–72.

Ground contact and particle radius¶

Particles land on Ground. Their centers sit approximately one Radius above the surface. Bounciness controls rebound; Friction reduces sliding at contact.

Particles can overlap each other here. Collision handles the assigned ground; Granular or Self Collision would add particle-to-particle contact.

Keep physical Radius 0.025 m and Substeps 4 while checking contact. Increasing Point Cloud display size does not enlarge the physical contact radius.

Optional: compare bounce and friction¶

Compare Bounciness 0 and 0.6, with a replay from frame 1. Restore 0.2. Compare Friction 0 and 0.8 separately, then restore 0.5.

Troubleshooting¶

• Particles pass through: check the collider and effect, apply scale, then increase Substeps only if fast motion still misses contact.
• A visible gap remains: inspect Radius and collider padding or offset before moving Ground.
• The mound does not support itself: this setup has no particle contact solver. Use the Sand Pile workflow.

Reference: Collision.

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