Real-Time Animation of Realistic Virtual Humans

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Real-Time Animation of Realistic Virtual Humans. Real-Time Animation of Realistic Virtual Humans. Real-Time Animation of Realistic Virtual Humans. 1. The 3D virtual player is controlled by the real people who has a HMD and many sensors
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Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans1. The 3D virtual player is controlled by the real people who has a HMD and many sensors 2. Unlike in video games, animation is not predefined.3. Unlike in rending films, animation is in real-time.Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansTo achieve a real-time virtual humans application we need to consider:1. Modeling people.
  • How to present deformation of human body.
  • Motion control.
  • Real-Time Animation of Realistic Virtual Humans1.Body Creation and Skeleton Animation -Zhou Bin2.Facial Deformation -Hu Yi3. Body Deformation and Animation Framework -Yang YufeiReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansBody Creation:First layer: Skeleton hierarchy. Second layer: Metaballs attached on the skeleton. Third layer: Convert metaballs to mesh surface (skin mesh). Fourth layer: Texture.Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFirst layer: Skeleton hierarchy1. Skeleton articulated just similar to real human. 2. We can define all the human postures using this skeleton. 3. Relative limb sizes of the skeleton decides the figure of the virtual people. Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansSecond layer: Metaballs attached on the skeletonConstruct human body by column.Can’t avoid gap on human body.Construct human body by column and sphere joint. Can avoid gap butcan’t present human body’s smoothand gradual shape.Construct human body by metaballs.Metaballs includes spheres and ellipsoids. Left figure is constructed by two ellipsoids. Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansSecond layer: Metaballs attached on the skeleton1.These two human models are assembled by Metaballs (ellipsoid components). 2. Metaballs are smooth and gradual, so they are suitable for modeling human bodies3. Different color depends on the attributes of that metaball: blendable or unblendable, deformable or nondeformable. Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansThird layer: Convert metaballs to mesh surfaces (skin mesh).1. Convert metaballs to a number of meshes. We can do this job by doing ray tracing, and sampling the intersection points. 2. These meshes can decide the lighting effect of human bodies.3. Texture mapping corresponds to these mesh surfaces.Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFourth layer: Mapping textureReal human hand texture3D Bernard Boxton without texture3D Bernard BoxtonTexturing has low cost of computation but can observably improves the quality of the virtualobject.Textured 3D modelReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansBody Animation: First layer: Skeleton motion. --Let avatars make postures and actions. Second layer: Mesh surface (skin mesh) deformation. --Present deformation of humans’ skin.Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansSkeleton: 1. The hierarchy of skeleton is defined by a set of joints. This set of joints corresponds to the main joints of real humans 2. Each joint consists of a set of degrees of freedom (DOF). DOFs decide ranges of the joint can translate and rotate. Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansThree methods of skeleton motion control: 1. The skeleton motion is captured in real time and drives the avatar. 2. The skeleton motion is predefined. It will be activated from a database as a response to human’s input. E.g. Sony’s Eye Toy. 3. The skeleton motion is dynamically calculated. Doesn’t require a user’s continual intervention. E.g. complex games, and AI application. Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansHuman Head Modeling Facial Animation
  • To simulate humans requires real-time visualization and animation.
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansHuman Head Modeling
  • Scanning
  • scan the surface of the head and construct a head model
  • Use a sculpturing model----Software Sculptor
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansUse a sculpturing model----Software SculptorReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFacial Animation
  • Facial deformation model
  • Facial motion control
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFacial Deformation Model
  • Consider human face as a polygonal mesh
  • Define regions on the mesh
  • Define a control lattice on the region of interest
  • Muscle actions are simulated by changing the control points’ weight
  • A stiffness factor allows the amount of deformation for each point
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFacial Deformation ModelReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansFacial Motion ControlReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans The Facial Action Coding System
  • Define basic motion parameters as minimum perceptible actions (MPAs)
  • open_mouth, close_upper_eyelids, or raise_corner_lip Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans The Facial Action Coding System
  • Each MPA has a corresponding set of visible features
  • e.g. movement of eyebrows, jaw, or mouth Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans The Facial Action Coding System
  • Real-time facial animation module uses three different input methods
  • Video
  • Audio or Speech
  • Predefined Actions
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansVideo Input
  • Recognition and tracking of the facial features is based on color sample identification, edge detection, and other image processing operations. The feature capture and tracking rate is about 20 frames per second (fps)
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansAudio Input segment audio into phonemes with their durationText input to phonemes phonemes decomposes into MPAs
  • Predefined Action
  • an action that has intensity, duration, and a start time
  • e.g.emotion (surprise, anger)
  • head gestures (nodding, turning)
  • decomposes into MPAs
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humanspredefined action of speechinputaudio inputvideo inputinterpolationSynchronization go to the composerReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansComposition defined a sinusoidweight functionconsidered 10 percent of the action’s total durationno jump effectwith the same MPA overlapReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans Body deformations
  • The ways we do the representing humans
  • Polygonal representation
  • Visual accuracy representation
  • The combination of previous two
  • Implement results
  • Animation framework
  • Two case studies
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansThe first method
  • Body deformation
  • Polygonal representation
  • Visual accuracy representation
  • The skin wrapped around the skeleton is represented with a fixed mesh divided at important joints where deformations occur.
  • The combined method
  • Pros
  • Simple and easy to implement
  • Cons
  • The virtual human appears “rigid” and lacks realism
  • Visually distracting artifacts may arise at joints
  • Image from the internetReal-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The second method
  • Polygonal representation
  • Visual accuracy representation
  • The combined method
  • The application compute the skin from implicit primitives and use a physical model to deform the body’s envelope.
  • Pros
  • Stress visual accuracy and yields very satisfactory results in terms of realism
  • Cons
  • So computationally demanding
  • Unsuitable for real-time applications
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The third method
  • Polygonal representation
  • Visual accuracy representation
  • The combined method
  • It’s a combination of previous two methods, allowing a good trade-off between realism and rendering speed.
  • Steps
  • Constructing a body mesh
  • Deforming by manipulating skin contours
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The combined method --- step one
  • The combined method
  • Constructing the body mesh
  • Manipulating skin contours
  • Output the body data as cross-sectional contours.
  • Convert contours data to triangle meshes.
  • Easy to render, performs better
  • Construct a triangle strip by connecting the points from two adjacent cross-section
  • Connecting two different body parts proves a bit more complicated.
  • Image from: Daniel Thalmann, Jianhua Shen, Eric Chauvineau, 1996Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The combined method --- step two
  • The combined method
  • Constructing the body mesh
  • Manipulating skin contours
  • Transform a complicated 3D operation into a 2D operation by manipulate the cross-section contours.
  • By setting the orientation and position of the plane in which every contour lies, we can achieve a smooth deformation of the skin.
  • Image from: Daniel Thalmann, Jianhua Shen, Eric Chauvineau, 1996Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The combined method --- step two (cont.)
  • The combined method
  • Constructing the body mesh
  • Manipulating skin contours
  • Very joint lies in the plane of its contour when the skeleton is in the at-rest posture.
  • Two segments of the arm whose directions are L1 and L2.
  • Nu, N0 and Nl are the normal vectors of the cross-section planes.
  • Oi and Ni are the center and normal respectively of the ith cross-section plane.
  • Since we know Ni by
  • interpolation, we can compute each vertex belonging to the ith contour.Image from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual Humans
  • Body deformation
  • The combined method --- step two (conclusion)
  • The combined method
  • Constructing the body mesh
  • Manipulating skin contours
  • The contours run parallel at the region above the elbow.
  • This is because our eyes naturally go to the areas surrounding major joints like the elbows or knees.
  • Practically we determined the number of upper and lower contours to deform in a heuristic fashion.
  • It saves the rendering time and has little degradation.
  • Image from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansResults
  • Using real-time-oriented 3D graphics toolkit called Performer.
  • In right image: the virtual human on the left is made up of 14,000 vertices and containing 13,500 textured triangles using deformation; on the right uses rigid meshes with 17,000 triangles.
  • Image and figure from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansAnimation framework
  • The close link between modeling and animation.
  • The system separates into three units: modeling, deformation and motion control.
  • Modeling provides geometrical models for the body, hands and face.
  • Deformations are performed separately on different entities based on the model used for each part.
  • Motion control generates and controls the movements for different entities.
  • Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansAnimation frameworkFigure from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansCase studies--- CyberTennisImage from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998Real-Time Animation of Realistic Virtual HumansReal-Time Animation of Realistic Virtual HumansCase studies--- CyberDanceImage from:Prem Kalra, Nadia Magnenat-Thalmann, Laurent Moccozet, and Gael Sannier, 1998
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