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This section describes how to rig a model for season blending.


The interface for season changing is split between the ‘Timeline’ bar, the ‘Growth’ property groups on leaf generators/nodes, and the material assets. The general procedure for making a model undergo a season change is as follows:

  • Create the model as you would any other model. Leave season disabled.
  • Setup each leaf material to have Spring/Summer leaves in the diffuse slot and Fall leaves in the detail slot.
  • Enable ‘Season’ on the ‘Timeline’ bar. Use the season curve and the time slider to preview the animation.
  • Tune the behavior by editing the properties in each leaf generator’s ‘Season’ group.

When you select a time on the timeline bar a season value from 0.0 (beginning of the season) to 1.0 (end of the season) is computed based on the 'Season' curve. This value is used to drive the season change mechanism of each leaf.

Each leaf will compute a transition state based on the global season value. This value is used to blend between the diffuse map of the material and the detail map. The profile curve on the 'Change duration' property can be used to make the edges of the leaf turn before the anchor point. The two texture blending approach provides a mechanism for every leaf in a transition state to have slightly different colors.

You can make even more variations by adding multiple leaf materials, mixing and matching Spring/Fall maps, and using the color adjustment options on the material asset. Each new, different leaf material will make new variations.

You can preview the season effect by scrubbing the timeline bar. If your tree computes slowly you can speed up the preview either by hiding/unlinking generators or using the new ‘Focus’ feature. Click the 'Focus:Target' button on the toolbar and then click a branch on the tree model. All subsequent computes (including growth) will be limited to the selected node and its children until the 'Focus:Clear' button is pressed. This is often the best way to get an interactive preview of the season process.

Another way to see a quick preview of the season animation is to use the 'Export image sequence' option in the 'File' menu to create a sequence of images rendered from the Modeler.

The season change mechanism does not include falling leaves (although you can control how and when dead leaves are removed using the 'Season' properties in the leaf generator).

Timeline Bar

The ‘Timeline’ bar (pictured below and accessed via WindowTimeline from the main menu) is where season changing is enabled/disabled. Use the 'Season' curve to change the timing of season changes.


Currently, the goal of the season system is to export a model at a specific season state. Set the timeline bar to the desired frame and export it like you would any other model.

In order to see the color blending in your rendering app you must do one of the following actions:

  • Export to Cinema4D - Everything is handled automatically.
  • Export to FBX and load the model with our 3ds Max or Maya import scripts - Shaders are automatically computed to implement the leaf blending for Mental Ray
  • Export to FBX and create a custom shader - The blend factor for the leaf material is stored in the detail map U coordinate if, and only if, the detail map V coordinate is less than -999.0f. Please contact support for help on implementing this in your pipeline.