Automatic Data Normalization and Parameterization for Optical Motion Tracking

Methods for optical motion capture often require timeconsuming manual processing before the data can be used for subsequent tasks such as retargeting or character animation. These processing steps restrict the applicability of motion capturing especially for dynamic VR-environments with real time requirements. To solve these problems, we present two additional, fast and automatic processing stages based on our motion capture pipeline presented in [HSK05]. A normalization step aligns the recorded coordinate systems with the skeleton structure to yield a common and intuitive data basis across different recording sessions. A second step computes a parameterization based on automatically extracted main movement axes to generate a compact motion description. Our method does not restrict the placement of marker bodies nor the recording setup, and only requires a short calibration phase.

Subsecond changes of global brain state in illusory multistable motion perception

This study explored transient changes in EEG microstates and spatial Omega complexity associated with changes in multistable perception. 21-channel EEG was recorded from 13 healthy subjects viewing an alternating dot pattern that induced illusory motion with ambiguous direction. Baseline epochs with stable motion direction were compared to epochs immediately preceding stimuli that were perceived with changed motion direction ('reference stimuli'). About 750 ms before reference stimuli, Omega complexity decreased as compared to baseline, and two of four classes of EEG microstates changed their probability of occurrence. About 300 ms before reference stimuli, Omega complexity increased and the previous deviations of EEG microstates were reversed. Given earlier results on Omega complexity and microstates, these sub-second EEG changes might parallel longer-lasting fluctuations in vigilance. Assumedly, the discontinuities of illusory motion thus occur during sub-second dips in arousal, and the following reconstruction of the illusion coincides with a state of relative over-arousal.

Multi-Mode Tensor Representation of Motion Data

In this paper, we investigate how a multilinear model can be used to represent human motion data. Based on technical modes (referring to degrees of freedom and number of frames) and natural modes that typically appear in the context of a motion capture session (referring to actor, style, and repetition), the motion data is encoded in form of a high-order tensor. This tensor is then reduced by using N-mode singular value decomposition. Our experiments show that the reduced model approximates the original motion better then previously introduced PCA-based approaches. Furthermore, we discuss how the tensor representation may be used as a valuable tool for the synthesis of new motions.

Registration of Sub-Sequence and Multi-Camera Reconstructions for Camera Motion Estimation

This paper presents different application scenarios for which the registration of sub-sequence reconstructions or multi-camera reconstructions is essential for successful camera motion estimation and 3D reconstruction from video. The registration is achieved by merging unconnected feature point tracks between the reconstructions. One application is drift removal for sequential camera motion estimation of long sequences. The state-of-the-art in drift removal is to apply a RANSAC approach to find unconnected feature point tracks. In this paper an alternative spectral algorithm for pairwise matching of unconnected feature point tracks is used. It is then shown that the algorithms can be combined and applied to novel scenarios where independent camera motion estimations must be registered into a common global coordinate system. In the first scenario multiple moving cameras, which capture the same scene simultaneously, are registered. A second new scenario occurs in situations where the tracking of feature points during sequential camera motion estimation fails completely, e.g., due to large occluding objects in the foreground, and the unconnected tracks of the independent reconstructions must be merged. In the third scenario image sequences of the same scene, which are captured under different illuminations, are registered. Several experiments with challenging real video sequences demonstrate that the presented techniques work in practice.

Real-time Human Motion Capture with Simple Marker Sets and Monocular Video

In this paper we present a hybrid method to track human motions in real-time. With simplified marker sets and monocular video input, the strength of both marker-based and marker-free motion capturing are utilized: A cumbersome marker calibration is avoided while the robustness of the marker-free tracking is enhanced by referencing the tracked marker positions. An improved inverse kinematics solver is employed for real-time pose estimation. A computer-visionbased approach is applied to refine the pose estimation and reduce the ambiguity of the inverse kinematics solutions. We use this hybrid method to capture typical table tennis upper body movements in a real-time virtual reality application.

Estimating Gesture Accuracy in Motion-Based Health Games

This manuscript details a technique for estimating gesture accuracy within the context of motion-based health video games using the MICROSOFT KINECT. We created a physical therapy game that requires players to imitate clinically significant reference gestures. Player performance is represented by the degree of similarity between the performed and reference gestures and is quantified by collecting the Euler angles of the player's gestures, converting them to a three-dimensional vector, and comparing the magnitude between the vectors. Lower difference values represent greater gestural correspondence and therefore greater player performance. A group of thirty-one subjects was tested. Subjects achieved gestural correspondence sufficient to complete the game's objectives while also improving their ability to perform reference gestures accurately.

Intensive Rotational Grazing of Steers at the Andrew Jackson Demonstration Farm

Fifty head of crossbred steers started grazing 51 acres of pasture on May 1 in a rotational grazing system using a variable density paddock system. Twenty-two head grazed 92 days, 27 grazed 140 days, and one steer died. A total of 11,922 pounds was produced on 5,804 animal-days of grazing. The average daily gain was 2.02 pounds for group 1 and 2.07 for group 2. The stocking rate for the first 92 days was .98 steers per acre and .53 for the final 48 days. The animal days of grazing per acre was 113 and the pounds of gain per acre was 233. Total return for land, labor and management for the demonstration was $2,829.76 or $55.49/acre.

Evaluation of Hay-Type and Grazing Tolerant Alfalfa Hybrids in Season-Long or Complementary Rotational Stocking Systems for Beef Cows

Pastures containing hay-type and grazing tolerant alfalfa hybrids were grazed in a season-long or complementary rotational stocking system with Nfertilized smooth bromegrass. The pastures were stocked at a seasonal density of .8 cow-calf pairs per acre for 120 days in 1998 and 141 days in 1999. Pastures were intensively managed by daily stripstocking with the assumptions that 50% of live forage was available and daily live dry matter consumption of each cow-calf pair was 3.5% of the cow’s body weight. First-cutting forage was harvested as hay from 40% of the pasture acres to remove excess forage growth early in the grazing season. Grazing occurred on the remaining 60% of each pasture for the first 44 and 54 days and 100% of each pasture after days 45 and 55 in 1998 and 1999, respectively. Proportions of ‘Amerigraze’ and ‘Affinity’ alfalfa in the live forage dry matter decreased by 70% and 55% in pastures stocked season-long and by 60% and 42% in pastures used for complementary stocking (alfalfa type, p<.05; grazing management, p<.05) in 1998, but decreased by a mean of 72% and was unaffected by hybrid or stocking system in 1999. Cows grazing either alfalfa hybrid by either grazing system had greater weight gains during the breeding and overall grazing seasons and greater increases in body condition score pre-breeding and during the breeding season than the cows that grazed smooth bromegrass for the entire season in 1998. Also, cows grazing either alfalfa hybrid in the season-long system had greater breeding season increases in body condition score than cows grazing alfalfa in the complementary system with smooth bromegrass in 1998. Cows grazing in the season-long alfalfa system had greater prebreeding season weight (p<.10) increases and condition score (p<.05) increases than cows grazing alfalfa in the complementary system in 1999. Daily and seasonal body weight gains of calves were not affected (p>.10) by the presence of alfalfa in 1998 or by alfalfa type and grazing management in 1998 and 1999. Total animal production (cow and calf) in 1998 was greater (p<.10) from the season-long alfalfa pastures compared with the complementary stocked pastures. Total (p<.10) and live (p<.05) forage masses, estimated by monthly clippings, were greater in September of 1998 from the season-long alfalfa pastures than pastures using alfalfa for complementary stocking. Total (p<.10) and live (p<.05) forage masses were greater in August of 1999 from season-long alfalfa pastures than pastures using alfalfa for complementary stocking.

Evaluation of Hay-Type and Grazing Tolerant Alfalfa Hybrids in Season-Long or Complementary Rotational Stocking Systems for Beef Cows

Pastures containing hay-type and grazing tolerant alfalfa hybrids were grazed in a season-long or complimentary rotational stocking system with Nfertilized smooth bromegrass. The pastures were stocked at a seasonal density of .8 cow-calf pairs per acre for 120 days. Pastures were intensively managed by daily strip-stocking with the assumptions that 50% of live forage was available and daily live dry matter consumption of each cow-calf pair was 3.5% of the cow’s body weight. First-cutting forage was harvested as hay from 40% of pasture acres to remove excess forage growth early in the grazing season. Forage was grazed from the remaining 60% of each pasture for the first 44 days of the experiment and then from the entire pasture thereafter. Live forage yields, estimated by monthly clippings, were greater in May and September on the season-long alfalfa pastures compared with the complementary pastures and on the alfalfa pastures compared with the N-fertilized smooth bromegrass pastures. The proportions of legumes in the live dry matter in pastures with grazing tolerant and hay-type alfalfas in the season-long grazing systems declined by 70% and 50%, respectively, in the 120 day trial. The proportions of legumes in the live dry matter in pastures with grazing tolerant and the hay-type alfalfas in the complementary grazing system declined 60% and 42%, respectively, in the 120 day trial. Cows grazing either alfalfa hybrid by either management system had greater weight gains during the breeding and grazing seasons and greater increases in body condition score prebreeding and during the breeding season than the cows that grazed N-fertilized smooth bromegrass for the entire season. Also, cows grazing either alfalfa in the season-long system had greater breeding season increases in body condition score than cows grazing alfalfa in the complementary system with N-fertilized smooth bromegrass. Daily gains and seasonal gains of calves from cows grazing the alfalfa pastures tended to be greater than those grazing N-fertilized smooth bromegrass. Within alfalfa treatments, calves of cows grazing alfalfa pastures in the season-long system tended to produce more pounds per acre than those of cows grazing alfalfa in the complementary systems.

Alternative Rotational Grazing Systems at the Beef Teaching Farm

Fifty-six acres of central Iowa corn land were seeded to bromegrass and divided with high-tensile wire into eight seven-acre plots. This bromegrass was fertilized with 70 pounds of nitrogen each spring and fall, 1987-1990. In 1991 – 1995, the nitrogen was increased to 80 pounds both spring and fall. The plots were stocked with 1.3 cow/calf pairs per acre in 1987-1991 and 1993–1995, but in 1992 the plots were stocked with 1.55 cow/calf pairs per acre. The pairs were rotated using two distinct schemes among four cells for about 150 days. The plots averaged 607 pounds of net calf weight per acre per year over nine years. Rainfall was quite variable during the grazing seasons and was reflected in calf performance as well as summer feed costs. This intensive rotational grazing system has greatly reduced both weed population and the need for mechanical clipping.