Leaf mesh generator properties

The Leaf mesh generator is responsible for generating leaves based on materials and mesh assets. Leaf mesh generators (along with Batched leaf generators) are the primary mechanism by which season transitions occur.

Generation

The properties in this group control how many leaves are generated and where they are placed. Refer to Generation properties.

Forces

The properties in this group control how forces affect the nodes created by this generator. Forces affect only the orientation, not the position, of leaf meshes.

Forces

Property	Description
Allow	When enabled, all forces that are checked will act on the generator.
(Force names)	Each force in the scene has an entry here. Check the box next to the name to enable the force for this generator. The value set here is multiplied by the strength of the force before being applied to the branch. The profile curve controls have no effect on leaves.

Note

Select the force name to edit the force's properties.

Align

Each force has an Align strength in addition to its main strength. This strength causes the original orientation to be affected by the force.

Property	Description
Style	Choose the style of the alignment operations from the following options. None: No alignment will take place. Individual: Each node is aligned without regard for the behavior of any of its siblings. Group: A single alignment is computed for all siblings.
Amount	The alignment strength of each enabled force is multiplied by this amount before being applied.
Match branch parent	Match the force alignment with that of the parent node.

Geometry

The properties in this group control the behavior of leaves when they collide with a geometry force.

Property	Description
Kill action	Choose when to remove leaves that collide with a geometry force. None: Don’t remove leaves. Quick: Remove leaves early in the compute process based on a rough estimate of leaf size. Accurate: Remove leaves after they compute based on the actual leaf geometry.
Tolerance	Set how tolerant of collisions the algorithm should be. Larger values mean more of the leaves will intersect.

Random Seeds

Refer to Random seeds properties.

Leaves

The properties in this group control the type, size, and initial placement of the leaf nodes.

Property	Description
Use actual size	When enabled, the size parameter is ignored and the mesh is used at exactly the size at which it was modeled.
Size	This property sets the size of the leaf nodes. By default, mesh assets are treated as unit meshes and then scaled by this amount when placed on the model.
+% of parent	Increase the size of the leaf nodes by this value multiplied by the size of the parent.
Weld	When enabled, leaves will be placed directly on the skin of their parent (as opposed to being anchored on their spine).
Keep failed welds	When enabled, leaves that failed to weld are still computed. Use this to help find and correct failed welds in critical regions (failed welds in fine detail areas are often okay).
Cross	When enabled, leaves are rotated so that they are perpendicular to the original leaf placement. This is a shortcut for creating crossed, intersecting meshes that have the same position.
Fix winding	When enabled, the face winding of the polygons in the final mesh is adjusted to match the direction of the surface normals. This correction is applied after vertex deformation and lighting adjustments.
Flip	When enabled, randomly selected leaf nodes are flipped over the y-axis.
Initial orientation	Orient all nodes in this generator based on the below options. This property is only available if Flip is disabled. Classic: Orient nodes based on whether they’re on the left or right side of the model. Works best in Phyllotaxy generation mode and results in more organic shapes. Synchronized: Orient all nodes in the same direction relative to the parent.

Type

The properties in this group specify the materials and meshes for the leaf. Meshes must be assigned to the material on the Material Bar to be used on the leaf. Materials are chosen based on their weights and season settings.

Property	Description
Material	This property specifies a named material from the Material Bar. If None is selected or the chosen material has no assigned mesh, a simple square will be used as placeholder geometry.
Mesh	Use this property to choose a particular mesh from the material asset or allow it to pick randomly (Any), the first mesh on the asset (Primary), or any mesh but the first (Not primary).
Weight	Sets probability that a node will receive this material (this weight ÷ sum of all weights).

Resolution

The properties in this group influence the resolution of the mesh.

Property	Description
Size increase %	This curve controls the increase in the size of the leaf nodes as the resolution changes. It is often desirable to increase the size of the leaves at lower resolutions to make up for a lower number of leaves.
Mesh LOD	This curve sets which mesh version (High, Medium, or Low detail on the mesh asset) is used based on the active resolution.
Mesh LOD offset	When set to a value other than 0, the mesh currently assigned will go up or down in mesh resolution (High, Medium, or Low detail on the mesh asset). Use this property (especially in conjunction with its parent curve) to adjust mesh resolution throughout the model.

Note

Mesh LOD and Mesh LOD offset both require meshes assigned in at least two of the three mesh asset LOD slots.

Local Orientation

The properties in this group are the first stage of orienting the leaf. The orientation actions are performed in the order in which the properties are listed.

Property	Description
3D anchor style	Set how 3D anchors align with the orientation of the parent node. Legacy: Ignore the orientation and deformations of the parent node. Use this setting if the parent node is a leaf and the parent orientation should be ignored. Match parent: Follow the orientation and deformations of the parent node.
Unification	Uses the anchor to orient itself "out" before the rest of the orientation adjustments are performed. The "Out" direction is considered to be the vector from the anchor point through the node's attachment point. Anchor point placement options are as follows: Global: The anchor point is located where the node's highest ancestor hits the ground. Deep: The anchor point is the base of a node very near (and sometimes exactly on) the root of the node's ancestors. Intermediate: The anchor point is somewhere in the middle of the node's ancestors. Local: The anchor point is very near where the node is attached. None: No anchor point is computed, and no unification is done.
Sky influence	Controls how much the leaves point toward the sky. Higher numbers result in the z-axis of each mesh pointing straight up.
Fold	Rotates leaves up or down around the parent's growth direction.
Align	Rotates the tip of the leaves toward or away from the parent's growth direction. Use this property to point leaves in the direction the parent is growing.
Face	Spins the leaves around their stem so that their up vector points in the direction of the parent's growth. Use this property to make the leaves face out relative to their parent.

Note

Interval and Phyllotaxy generation modes work best with these properties. These modes give each leaf an idea of which side they're on. Doing so makes a positive value for Align, Face, and Fold all work the same, regardless where the leaf was generated.

Sensitivity

The properties in this group control the second stage of leaf orientation.

Parent

Parent sensitivity refers to orienting the leaf based on where it is positioned relative to its ancestors.

Property	Description
Amount	Sets the amount that the bottom of the leaf is turned to face the point set by Anchor.
Anchor	This property picks a spot on one of the leaf's ancestors according to the following options: Global: The anchor point is located where the node's highest ancestor hits the ground. Deep: The anchor point is the base of a node very near (and sometimes exactly on) the root of the node's ancestors. Intermediate: The anchor point is somewhere in the middle of the node's ancestors. Local: The anchor point is very near where the node is attached. None: No anchor point is computed, and no parent sensitivity is added.
Sky	Rotates the mesh around its central axis to get its z-axis as close to up as it can. Think of it as the leaves rotating around their stem to face the light.

Final Adjustments

These edits are applied to the leaf meshes as a group after Local Orientation and Sensitivity compute.

Property	Description
Up	Rotates each mesh around its local x-axis.
Right	Rotates each mesh around its local y-axis.
Out	Rotates each mesh around its local z-axis.

Deformation

The properties in this group alter the shape of the leaf mesh. These properties work best when there are enough vertices in the mesh to reveal the changes.

Note

Using these properties on low-resolution meshes can produce undesirable results. You should always have at least one vertex near the center of the mesh for the best results.

Property	Description
Height	Displace the leaf geometry based on the height map of the assigned material.
Fold	Folds both sides of the leaf lengthwise along the y-axis of the mesh. A negative value bends down, while a positive value bends up.
Curl	Curls the leaf around the mesh's x-axis.
Twist	Twists the leaf around the mesh's y-axis. The farther away a vertex is from the x-axis, the more it is rotated.

Vertex

The properties in this group perform a noise-based deformation of each vertex in the mesh.

Property	Description
Amount	This property controls the amount of noise applied to each vertex.
Noise	This value controls the tightness of the noise pattern. Higher values result in more localized deformations.
Seed	Vary this parameter to randomize the noise pattern.

Scale

The properties in this group scale the mesh. The scale is performed in each leaf's local orientation.

Property	Description
X	Scales the mesh by this amount in the x-axis.
Y	Scales the mesh by this amount in the y-axis.
Z	Scales the mesh by this amount in the z-axis.

Lighting

The properties in this group modify the vertex normals to change the lighting behavior of the mesh.

Note

These properties are not typically necessary for high-detail VFX models but they can significantly improve the lighting on meshes that represent clusters of leaves in real-time models.

Property	Description
Style	Choose an approach to edit the vertex normals for this generator. The Lighting group properties differ for each option. Global: Edit this generator as part of a larger group with global lighting properties. Local: Edit this generator individually with local lighting properties.

Lighting (local)

Property	Description
Smooth	Use this property to compute smooth normals based on the average face normals at each vertex after the deformations have been computed. A value of zero means no smoothing, a value of 1.0 means completely smoothed normals. The other lighting adjustments in this group are applied after smoothing.

Parent Puffiness

Note

Select a leaf with hints on to see the Parent puffiness vectors.

Property	Description
Amount	Value scale that controls how much the normals on each individual leaf should face "out" depending on the assigned anchor point. A value of 1.0 makes each normal line up with the vector that goes from the anchor through the vertex.
Anchor	This property picks a spot on one of the leaf's ancestors according to the following options: Global: The anchor point is located where the node's highest ancestor hits the ground. Deep: The anchor point is the base of a node very near (and sometimes exactly on) the root of the node's ancestors. Intermediate: The anchor point is somewhere in the middle of the node's ancestors. Local: The anchor point is very near where the node is attached. None: No anchor point is computed, and no parent puffiness is added. Height: The anchor point is located where the node's highest ancestor hits the ground. Properties in the Anchor Shift section move the anchor directly up rather than along the ancestor. Surface X: The normals align with the x-axis of the parent where the node attaches. Surface Y: The normals align with the y-axis of the parent where the node attaches. Surface Z: The normals align with the z-axis of the parent where the node attaches.

Anchor Shift

Adjust where the anchor sits on the ancestor.

Property	Description
Position	Adjust the height of the anchor point on the ancestor. Note that the Amount value must be more than 0 for this property to work.
Amount	Set the range in which the anchor point moves when the Position value changes.
Puffiness	After all normal adjustments have been performed, this value “sphere-izes” the normals around the center of the mesh, giving the geometry a more puffy appearance.
Unify	This property causes all vertex normals to point in the average direction of all of the vertex normals. Use this property to align the normals to help localize specular effects.

Adjustments

The properties in this group rotate the normals of each leaf without rotating the geometry. These properties are commonly used when creating clusters.

Note

Apply variance to these properties to make leaves in a cluster appear jumbled when lit in the final model.

Property	Description
Up	This property rotates vertex normals around the local x-axis.
Right	This property rotates vertex normals around the local y-axis.
Out	This property rotates vertex normals around the local z-axis.
World up	Point all vertex normals up. This property overrides all properties in the Puffiness and Adjustments sections. Use this property for uniform lighting on grass models.

Wind

The properties in this group influence how leaves are animated in wind simulations. There are separate settings for VFX, Games, Legacy UE4/Unity, and Lumberyard.

Property	Description
Weight	Use this property to scale how much the leaf moves during wind simulations. The amount and frequency of motion are set on the Fan object. The left-hand side of the profile curve corresponds to the pivot point. The right-hand side corresponds to the vertex farthest away. Note: The left-hand side of the profile curve must be zero to avoid disconnecting from the parent.
Cross	Increase the wind weight on vertices based on their distance from the mesh’s centerline on the x-axis. Use this property to show heavier wind impacts on the edges of leaves compared to the center. The right side of the curve corresponds to the edges of a mesh.
Group	In many wind styles, multiple wind groups are available. Use this property to specify which group the leaves belong to. The most common use of this feature is to have separate animation parameters for leaves and fruit.
Lock to parent	When enabled, leaves stay attached to their parent during wind animation but do so by sacrificing their own independent motion.

Growth

The properties in this group control how the model behaves during animated growth. In general, you create the model in the fully grown state and use these properties to control how it gets there.

Property	Description
Speed scale	The speed at which a leaf will grow is set on the Timeline Bar. Use this property to scale that value. The profile curve scales the speed relative to the leaf's total growth time. For example, ease in and out of the growth animation by using an S curve.
Smoothing	Leaves can be oriented based on the current state of their parent (0.0 smoothing), the final state of their parent (1.0 smoothing), or anywhere in between. Increase this value to prevent wild leaf motion during growth. This is especially useful for leaves growing off a twisted or gnarled parent.

Transitions

Property	Description
Size	This curve controls how the size increases over the course of the leaf's growth time.
Orientation	This value controls how much to rotate the leaf about its local x-axis at the start of its growth period. The profile curve controls how it transitions to the final orientation. The rightmost point of the profile curve must be at 1.0 to match the model as it appears when growth is disabled.
Curl	Adds additional curl to the leaf at the start of the growth. The profile curve sets how much of the additional curl is added during the growth cycle of the leaf.
Fold	Adds additional fold to the leaf at the start of the growth. The profile curve sets how much of the additional fold is added during the growth cycle of the leaf.

Timing

Property	Description
Style	Sets the conditions under which the leaf will start growing. The Start % property works according to the option selected here. Options include: In place: The leaf will start growing exactly when the parent is long enough to reach its starting point in the fully grown model. Start % has no effect. This style makes the animation appear to trace out the model. Parent: The growth of this leaf will be based on the growth of the parent. A Start % of 0.0 means start when the parent starts, 1.0 means start when the parent ends. Parent's start and end: The growth of this leaf will start and stop in perfect synchronization with its parent. Start % has no effect.
Start %	Causes leaves to start early (0.0) or late (1.0) according to the Style property.
Offset	The start frame is shifted by a constant number of frames (negative means earlier, positive means later). This value is best used to “jumble up” start times of neighboring leaves. Note: It is almost never a good idea to go negative with this value (leaves can't grow earlier than the structure will allow). A good practice is to have a value of something like 10 and a variance of 10 as well. That way the earliest any leaf will start is when it was supposed to, but some will be delayed.

Noise

The properties in these groups add noise to the growth animation to provide a more organic effect.

Wobble

Property	Description
Amount	Controls how much noise is applied when bringing the orientation into its final position. Note: The final value for the profile curve must be 0.0 in order for the model to exactly match its correct final position.
Frequency	Increases or decreases the frequency of the noise pattern used for orientation.

Speed

Property	Description
Amount	Controls how much noise is applied to the speed at which the leaf reaches its final position. Note: The final value for the profile curve must be 0.0 for the model to exactly match its correct final position.
Frequency	Increases or decreases the frequency of the noise pattern used for speed.
Seed	Change this value to vary the noise pattern.

Season

The properties in this group control how leaves transition in the seasons system, which affects their presence, shape and material changes. Leaf transitions are determined by looking up season curves based on the position of the season slider.

Property	Description
Start offset	Determines when the leaf starts to transition: 0.0 makes the transition start immediately, higher values delay the start, and negative values make it start sooner.
Time scale	Controls how long it takes for a leaf to complete its transition. Higher values accelerate the transition. The default value of 1.0 means one year.
Drop time	Controls how long the leaf remains attached. A leaf can drop no matter what material is assigned.
Droop	Makes the leaves droop as they transition.
Size	Makes the leaves change size as they transition.
Curl	Makes the leaves curl as they transition.
Fold	Makes the leaves fold as they transition.

Tip

Use variance on these properties to slightly randomize the time and effects of the transition on neighboring leaves.

Fallen

When Show dropped leaves is enabled on the Season Slider, the properties in this group influence the behavior of leaves on the ground (or ground mesh).

Property	Description
Ground duration	The amount of time the leaves stay on the ground before disappearing.
Spread	Controls how far from the point directly under the tree the leaf may travel before hitting the ground.
Flatten	Determines the amount of deformation removal ("Season:Curl" and "Season:Fold") applied to the fallen leaves.
Jumble	Randomizes the orientations of leaves on the ground.
Slope limit	If you have a force mesh applied to the leaf generator, fallen leaves will adhere to it instead of the ground. In that circumstance, use this property to keep leaves from gathering on slopes.

Dynamic LOD

The properties in this group control the LOD behavior of the leaves.

Property	Description
Weight	Increase or decrease the likelihood that leaves in this generator will survive the LOD process (vs. leaves in other generators). Use the parent curve to target specific areas of the model.
Scale factor	Leaves that survive the LOD process grow to fill the vacated space. The amount is set in the Tree generator's LOD section. This property scales that amount for leaves in this generator.
Mesh index	This curve controls which mesh LOD (if present) is used for each LOD state. The left side of the curve corresponds to the highest LOD. The right side corresponds to the lowest LOD.

Vertex Color

The properties in this group control how vertex colors are computed.

Note

Vertex colors must be enabled on the Tree generator for these properties to work.

Red

The properties in this group control how the red component of the color is computed.

Property	Description
Style	This property controls how the red portion of the color is computed from the following options: Set: Sets the color directly using the Value property (parent colors are ignored). Offset from parent: The Value property is added to the vertex color inherited from the parent.
Value	This property adds to, subtracts from, or directly sets this color component.

Green

The properties in this group control how the green component of the color is computed.

Property	Description
Style	This property controls how the green portion of the color is computed from the following options: Set: Sets the color directly using the Value property (parent colors are ignored). Offset from parent: The Value property is added to the vertex color inherited from the parent.
Value	This property adds to, subtracts from, or directly sets this color component.

Blue

The properties in this group control how the blue component of the color is computed.

Property	Description
Style	This property controls how the blue portion of the color is computed from the following options: Set: Sets the color directly using the Value property (parent colors are ignored). Offset from parent: The Value property is added to the vertex color inherited from the parent.
Value	This property adds to, subtracts from, or directly sets this color component.

Mesh Asset

The properties in this group control how vertex colors stored in the mesh asset are combined with the computed vertex colors.

Property	Description
Style	This property controls how mesh asset vertex colors are used from the following options: Interpolate: The Contribution value is used to blend from the computed to color (0.0) to the color stored in the asset (1.0). Add: The Contribution value is used to scale the mesh asset vertex color and the result is added to the computed vertex color.
Contribution	This value sets how much influence the mesh asset vertex color has on the final vertex color.

Post

The properties in this group influence how leaves in this generator participate in post-compute processing, such as leaf collision and shade pruning.

Property	Description
Take parent	When enabled, if a leaf in this generator is removed, its parent is also removed. Use this option to take away twigs supporting leaves that are removed.
Take descendants	If this leaf is eliminated during computations, checking this box will ensure that any of its children (and their children and so on) are also eliminated. This feature is useful when leaf meshes are used to represent image-based branches and have other leaves as children.

Collision

Define how the leaves in this generator participate in leaf collision.

Property	Description
Style	Set how the leaves behave during collision computations. Everything: Leaves in this generator collide with each other and all other leaves. Ignore siblings: Leaves in this generator ignore siblings but collide with everything else. Knock out others only: Leaves in this generator can’t be removed, but they can eliminate leaves in other generators. Nothing: These leaves don’t participate in collision computations.
Ignore parent	When enabled, leaves ignore their parent when checking collisions. This is useful when you're certain that the base of the leaf will frequently collide but the tips will not.
Weight	When leaves collide, the one with the higher weight wins. Use this property to set the weight.
Pivot threshold	Sets how far away from pivot (as a percentage of size) a collision has to happen in order to count. Use this property to eliminate unwanted removals of leaves anchored near each other.
Sphere threshold	When using spherical leaf collision tests, this value scales the size of the spheres used during the test. Spheres are initially sized based on leaf size.

See also the shared Post properties which apply to this feature.

Shade Pruning

Define how the leaves in this generator behave when you enable Shade Pruning.

Property	Description
Style	Select the layer of the tree to start pruning from. None: No leaves in this generator participate in shade pruning computations. Interior: The pruning starts from the most shaded leaves at the interior of the tree. Exterior: The pruning starts from the least shaded leaves at the exterior of the tree.
Threshold	Set the relative shade level up to which the Modeler removes leaves during pruning.

See also the shared Post properties which apply to this feature.

Lightmap

The property in this group affects the influence leaves in this generator have on the lightmap.

Note

Not all versions of the Modeler support lightmap UV computation.

Property	Description
Weight	Increase or decrease the importance of this generator's leaves in the lightmap – in relation to the lightmap weight of all other objects – before lightmap packing is determined. Note: Your Weight value may not be honored exactly or may get so large as to exhibit unexpected results. Use Tools > Reset lightmap scalars to go back to default values for the whole model.