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Abstract

We present a method for interactive modelling and animation of natural branching structures such as plants. Objects are created according to a rule based description. Geometric information is encapsulated in the objects and can be edited by methods such as free form deformation and spline techniques. Global and partial constraints allow the modelling of specific plants. The rule system is represented by a structure tree with components of high functionality that can be edited graphically. Keyframe techniques are applicable and allow to simulate parts of the models with local time. In comparison to other rule based approaches, complex branching structures can be developed faster and more flexible.

Animation(s)

These animation were created on a Silicon Graphics Maximum Impact with R4400/250MHz processor. The animation sequences are designed interactively and then rendered using an internal shader. Local times and iteration numbers of parts of the models like twigs and leaves are passed to the shader which modifies textures and colors according to that information.

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Fern (489kB) MPEG Movie
The keyframe sequences for a leaf is designed once and embedded into the keyframe sequence of a twig. Each time a twig generates a new leaf, a local time is assigned to the leaf and it grows according to that local time. A component arranges twigs according to the golden section. The animation of new twigs works the same as for the leaves.
225 frames rendered in 10 hours with 720x568 pixel on an Indigo Extreme R4400/135MHz.

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Ivy (460kB) MPEG Movie
This animation illustrates the use of global constraints. A field, defined via a special component, forces the ivy to grow around the stick. The appearance and developement of leaves is controled via embedded keyframing as described above.
300 frames rendered in 5 hours with 720x568 pixel on a Maximum Impact R4400/250MHz.

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Tree (679kB) MPEG Movie
This sequence is created for Bill Viola, an american video artist. It shows the whole life cycle of a tree compressed in one year. Blossoms and leaves are animated with embedded keyframing. They die at defined synchronization points in time. Local time and iteration numbers are used to modify the color of leaves over time individually.
224 frames rendered in 36 hours with 568x720 pixel on a Maximum Impact R4400/250MHz.