pGradientForce Node

pGradientForce reads a connected 2D image, computes its gradient (the direction in which luminance changes) and pushes particles along that gradient.

The result: particles "roll" from bright areas toward dark areas, like water flowing over terrain. Perfect for simulating directional fluids, currents, or stylized motion that follows an artistic pattern.

• Effects Library: Tools > Particles > pGradientForce
• Quick add: right-click in the Node Editor → Add Tool > Particles > pGradientForce

• Particle Input (orange) - particle stream.
• Gradient Image (green) - a 2D image with an alpha gradient that defines the direction and intensity of the force.
• Region Input (magenta/teal) - optional. Area where it applies.

Flow map with Fast Noise:
Fast Noise → pGradientForce Gradient input
pEmitter → pGradientForce → pRender
(particles follow an organic flow map)

Custom flow from an image:
Image (artistic, with values) → pGradientForce
pEmitter → pGradientForce → pRender
(direction controlled by an artistic drawing)

Current over 3D terrain:
Height map (Bump) → pGradientForce
pEmitter (above the terrain) → pGradientForce → pRender
(particles "flow" over the relief)

Strength

Intensity of the force. Positive = normal direction (white to black). Negative = reverse direction (black to white).

Random Seed

Seed for individual variations.

Conditions (Sets)

Force only on certain sets.

• Organic flow maps (Fast Noise) - a Fast Noise connected to the gradient input + pGradientForce = particles following a natural animated "fluid" pattern.
• Currents over terrain - the terrain's height map → pGradientForce = particles flowing like water over the relief.
• Custom artistic flow - a hand-drawn image (dark strokes where the particles should go) = artistic flow maps.
• Noise-based turbulent wind - an animated Fast Noise + pGradientForce = wind that changes direction following the noise pattern.
• Attraction/repulsion by image - an image with white areas (start) and black areas (destination) = particles migrating from light to dark.

• Animated Fast Noise = natural flow - the standard combo: Fast Noise (animated Seethe Rate) → pGradientForce = organic flow that evolves over time.
• Smooth gradient = smooth flow - images with hard transitions create abrupt forces. A light Blur on the gradient image smooths the trajectories.
• Negative Strength for reversed flow - from black to white instead of the other way around.
• Combine with pDirectionalForce - gravity + gradient force = particles that fall while following the gradient.
• For a true fluid simulation (water, realistic smoke), consider dedicated software. pGradientForce is for stylization.