Predictive Wet Ink Rendering for Stylus Latency Reduction
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Solution Overview
Problem
Current ink rendering techniques in tablet computing devices introduce significant latency, disrupting the user experience by lagging behind the fast input of pens and fingers, and often lack pressure sensitivity, which is essential for adapting ink width and other parameters.
Innovation Solution
The system generates predictive wet ink by calculating a predictive distance based on the current latency period and writing object velocity or acceleration, and uses writing object velocity as a proxy for pressure to set ink width and other parameters, even in non-pressure sensitive devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional ink rendering processing is used, then the system can process and display ink, but significant latency (50-100ms or greater) is introduced between user input and ink display
Solution Approach 1:
The system performs preliminary action by calculating predictive wet ink that anticipates where the writing object will be during the latency period. Instead of waiting for the actual input to be processed, the system proactively renders ink at predicted future positions based on current velocity and acceleration data, effectively pre-compensating for the known processing delay.
Solution Approach 2:
Predictive wet ink serves as an intermediary between the user's actual input and the rendered ink. This intermediate element bridges the temporal gap by displaying anticipated ink positions, making the latency imperceptible to users while maintaining the accuracy of the final ink placement.
2Device complexity
If non-pressure sensitive devices are used, then device complexity is reduced, but pressure data is unavailable for adapting ink width and parameters
Solution Approach 1:
The system changes parameters by substituting velocity data for pressure data. Since velocity can be accurately measured from position samples even on non-pressure sensitive devices, the system transforms the ink width determination parameter from pressure-dependent to velocity-dependent, maintaining adaptability without requiring additional hardware.
Solution Approach 2:
The system creates a functional copy of pressure data by using velocity information. Velocity serves as a proxy that replicates the information traditionally provided by pressure sensors, allowing the same ink adaptation algorithms to work on both pressure-sensitive and non-pressure-sensitive devices.
3Reliability
If ink rendering processes the input through multiple stages (digitization, OS processing, graphics card rendering), then comprehensive processing is achieved, but the latency increases significantly
Solution Approach 1:
The predictive wet ink calculation performs preliminary action by pre-computing ink positions during the ongoing input phase. This early computation overlaps with the natural processing pipeline, so when the actual ink rendering completes, the predictive ink is already prepared, effectively hiding the processing time from the user experience.
Data Source
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AI summary
Systems and methods are provided for improving the latency for display of ink during user creation of ink content with an object, such as a stylus, mouse, finger (or other touch input), or other drawing device. A touchscreen display device is configured to perform a method for assigning pressure data to contact points, comprising receiving a first contact point from the touchscreen that is not associated with pressure information, wherein the first contact point is one of a plurality of contact points on a path made by an object across a surface of the touchscreen; determining a velocity of the object at the first contact point; determining a pressure that corresponds to the velocity; associating the pressure with the first contact point to generate an updated first contact point; and using the updated first contact point to render a digital ink.