CG Character Eye Rigging with Angle Kappa Offset
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Solution Overview
Problem
Computer-generated character eyes often appear lifeless and unrealistic due to incorrect modeling of eye alignment and convergence, which fails to accurately simulate human binocular vision and stereo vision.
Innovation Solution
The system and method involve setting the rigging of each eye to be rotationally offset by an angle called 'Angle Kappa' (between 2° and 15°) to simulate correct physical eye positioning and movements, accounting for corneal refraction and shadowing effects to enhance realism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the optical axis of each eye is set to precisely converge on a target location, then the eye tracking model is mathematically simple, but the rendered eyes appear lifeless and unrealistic
Solution Approach 1:
The patent changes the optical parameters by introducing Angle Kappa (rotational offset between 2° and 15°) to offset the optical axis from the visual axis. This parameter modification allows the eyes to converge on targets while maintaining realistic outward pointing appearance, resolving the contradiction between mathematical simplicity and visual realism
Solution Approach 2:
The patent introduces an intermediary conceptual framework by distinguishing between the optical axis (geometric center) and visual axis (fovea alignment). This intermediary distinction allows the system to maintain both convergence functionality and realistic eye appearance simultaneously
2Measurement precision
If the eyes are modeled with precise convergence on targets, then the binocular vision model is mathematically accurate, but the final rendered images show dramatic differences from animator vision
Solution Approach 1:
The patent modifies the convergence model by applying rotational offset (Angle Kappa) to the optical axis, changing the parameters from precise geometric convergence to physiologically accurate convergence that matches human visual perception and animator vision
3Ease of operation
If the optical axis intersects the target precisely, then the eye tracking calculation is straightforward, but the eyes appear to cross excessively and look unnatural
Solution Approach 1:
The patent changes the operational parameters by introducing rotational offset angles (2°-15°) that reduce excessive convergence, making the eyes appear more natural while maintaining relatively straightforward calculation through modified optical axis orientation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach creates more realistic animated eyes by maintaining correct alignment and visual cues, ensuring consistency between animation and final rendering, and providing a convenient UI for animators to control eye movements and lighting effects.
Implementation Method 1
take account of the refractive properties of the cornea, e.g., which can make the pupil appear larger than it actually is
Data Source
AI summary
Systems and methods are provided to create better-looking animated eyes for CG characters. The systems and methods set the rigging of each eye to, rather than precisely converge on a target location, converge but be rotationally or angularly offset by a certain amount to simulate correct physical eye positioning and movements. In addition, the systems and methods provide even more realistic eye appearance by taking account of the refractive properties of the cornea, e.g., which can make the pupil appear larger than it actually is. The systems and methods may further take account of a shadowing effect of the upper eye caused by the brow, eyelashes, and upper lid (as well as an effect caused by reflection from the underside of the eyelashes). This darkening of the upper portion of the eye addresses vertical eyeline discrepancies caused by the visual and optical illusion of incorrect lighting.