Real-Time Dynamic Wrinkles

Caroline Larboulette

Marie-Paule Cani

GRAVIR Lab, Grenoble, France

Motivations

Animated wrinkles • Important for realism

– Cloth– Skin

• Currently painful under MAYA– Key shapes– Deformers

Aims• Real-time for computer games• Applicable to a coarse animated mesh• Easy to set up

Static wrinkle

Dynamicwrinkles

Previous Work

• Bump mapping [Blinn78, Boissieux00, Pasquariello01]

– Efficient but undeformed silhouette

• Physically-based approaches [Wu94-99, Boissieux00]

– Very realistic but slow

• Predefined Wrinkles [Viaud92]

– Specific mesh incorporating wrinkles• Displacement mapping [Volino99, Hadap99, Bando02]

– The user designs the wrinkle pattern

Our Wrinkling Tool

Basic Ideaskin/cloth wrinkle because they tend to maintain area

– Physically-based simulation, geometric constraints [sauvage04] ?

Aims– Fast approximation of constant surface– No manual design of the wrinkles shapes– Provide control of location and main direction of wrinkles

Our solution – A constant length wrinkling curve – Controls the mesh deformation in a region of influence

Wrinkling Curve

• 2D discrete curve of constant length

• Different propagation schemes

• Control of frequency, width of the bumps

Set up of the Wrinkling Tool

1. Draw a line segment• End points are anchored to the mesh

2. Specify a region of influence• Points under the green rectangle

3. Choose an attenuation profile

Mesh Deformation

• Mesh animated by standard skinning• Wrinkles updated just before rendering

Algorithm1. Update 2D curve due to length changes2. Refine mesh if needed3. Compute mesh vertices displacements

• Height given by the coordinate along the curve• Weighted according to the attenuation profile

Levels of Details

• Combination of bumps at different scales• Absorbs compression at different resolutions

Multi-Wrinkles

• Combination of several wrinkles

Results: forehead wrinkles

Results: joint wrinkles

Without our tool

With our tool

Results: wrinkles on clothesBack

Front

Video and demo

Conclusion

• Procedural technique – Mesh refined on the fly– Could depend on other parameters (camera)

• Easy-to-use for animators– Use of any existing skinning animation– Intuitive parameters and visual feedback

• Geometric constraints (length preservation)– Increases realism

• Real-Time

Future Work

• Curved Wrinkles

• Collision detection• Combination with a dynamic flesh model

Thanks ...

Questions ?