Attribute Flow¶

Run a flow simulation of an attribute across the surface of a mesh. This modifier has two versions with mostly identical settings:

Attribute Flow: Static flow simulation is calculated at once, number of iterations is specified up-front.
Attribute Flow Animated: Flow is calculated per frame.

Flow Steps¶

Getting the size of flow step for a mesh is important:

Too low = stepping artifacts.
Too high = very expensive.

Large step, low resolution:

Large step, high resolution:

Small step, high resolution:

Fade¶

The fade value can be positive or negative.

Positive values allow for darker areas to flow into lighter areas.
Negative values fade the attribute each iteration.

No Fade:

Positive Fade:

Negative Fade:

Streaks¶

Streaks are created by a random noise slowing down the flow, by adjusting this noise you can achieve a wide variety of streak styles

Flow Direction¶

The direction of flow can be based on a single direction or vector attribute. Random direction can then be mixed in. For completely random direction set direction to [0,0,0] and random value to 1.

Standard down direction:

Bidirectional on:

Fully random bidirectional:

You can use directions output by Curvature Direction. Bidirectional should be turned on because the curvature direction is bidirectional by default.

Base noise:

Flow along max curvature:

Flow along min curvature:

Outputs¶

Attribute: Output attribute with flow applied.
Color: Output flowed attribute as color (used for visualisation).

Settings¶

Attribute: Attribute to run flow simulation on.
Simulation: Calculate flow all at once or per frame:
- Static: Calculate all flow steps at once, independent of time.
- Animated: Calculate one step of flow per frame.

Direction¶

Direction of flow.

Space: Coordinate space of flow direction:
- Local: Flow direction is in local space (uses object rotation)
- Global: Flow direction is in global space (ignores object rotation)
Direction: Flow direction vector.
Random: Mix in random noise to flow direction. A value of 1 will completely ignore specified direction.

Random Noise¶

Noise settings for the random direction.

Noise Scale: Size of the largest features in the noise.
Octaves: The number of noise octaves. Higher values give more detailed noise but increase render time.
Roughness: Blend factor between an octave and its previous one. A value of zero corresponds to zero detail.
Noise Offset: Offset the noise W position. Effectively a smooth transition between seeds.

Flow Steps¶

Flow simulation settings.

Flow Iterations: How many iterations of flow to calculate.
Step Size: Maximum distance travelled by each flow step. Bigger step sizes are cheaper to calculate but can result in stepping artifacts.
Fade: Fade the head/tail of the flow simulation. Positive values will fade the tail (allowing darker areas to flow over lighter areas). Negative values fade the head resulting in a smooth fade out of the flow.
Minimum Angle Speed: Decrease flow speed depending on surface angle. 0 will completely stop flow on surfaces perpendicular to the flow direction. 1 will ignore the surface angle and full flow speed will occur everywhere.

Streaks¶

Add streaks/noise to the flow simulation.

Amount: Intensity of streaks applied to flow simulation.
Thickness: Scale of the noise used for streaks. Higher value = thicker streaks.
Offset: Offset the streak noise W position. Effectively a smooth transition between seeds.

Noise Values¶

Aditional noise settings to change the shape of streaks.

Noise Octaves: The number of noise octaves. Higher values give more detailed noise but are more expensive. Stop increasing when there is no visual impact.
Noise Roughness: Blend factor between an octave and its previous one. A value of zero corresponds to zero detail.
Stretch: Stretch the noise used for streaks in the flow direction. 0 = No stretch, uniform noise. 1 = Maximum stretch, 2D noise.
Contrast: Increase value contrast of noise, giving higher contrast streaks.
Bias: Midpoint of contrast operation. Higher values will produce a darker noise.

Mask¶

Mask flow with an attribute.

Attribute: Attribute to inhibit flow.