# The Method of Multi-Camera Layout in Motion Capture System for Diverse Small Animals
successfully captured and mapped out the wing trajectory of mosquitoes using eight high-speed cameras with an annular layout [16]. [PERSON] et al. also realized motion capture of small-sized hawk moths by employing three sets of high-speed cameras with orthogonal spatial layout [15]. Nevertheless, multi-camera systems typically achieve motion capture by using a higher number of cameras or using a single orthogonal layout. In addition, the measurement and analysis of behavioral observations and locomotor reaction forces have been widely used in the research and analysis of biological locomotion mechanics involving animals such as gecko [20; 21; 22], tree frog [23; 24; 25], spider [26], locust [27] and so forth, in particular, [PERSON], et al. was successful in obtaining the kinematic data for a rat's hind legs using four cameras set in two sides of a movement channel and force data were acquired via an action-reaction force measuring platform [28]. However, the occlusion problem still exists in stereovision if two cameras are used for three-dimensional positioning of an object. [PERSON], et al. has developed a 3D reaction force testing platform within a very small rectangular area (about 300 mm \(\times\) 100 mm), which has been successfully applied to measure the reaction force of various small animals [29]. Since behavioral observations and locomotor reaction force measurements are two key aspects in the study of animal locomotor behaviors, it is necessary to optimize the accuracy and efficiency of motion capture systems for effective integration with the small-scale force measurement platform. Therefore, it is important to the development of multi-camera layout methods that are matched to the different demand boundaries of small animals. Additional restrictions and constraints are placed on motion capture of biological objects, since diverse small animals have notable differences in their shapes and method of locomotion. Moreover, it is often necessary to obtain synchronous locomotor behavior of the animal's reaction force in a limited area. Therefore, we investigated the configuration and layout methods of multi-camera in motion capture system in-depth. The animals' locomotion demand boundaries including body shapes and locomotor behavior characteristics were analyzed and summarized. In addition, the capture characteristics of typical multi-camera layout patterns of one unit module were analyzed using theoretical calculation. The exact motion area which can be captured was then determined according to the relationship between the camera layout patterns and the depth range. Thus, the correlation between the layout patterns of a multi-camera system and the animal locomotion's capture demand boundaries was established and the matching mechanism between the patterns and diverse small animals is revealed. In this report, it was determined that the maximized intersecting volume of the visible field of the multi-camera and the reasonable modulation of the depth of field could effectively improve the accuracy of a motion capture system. Finally, typical small animals (gecko and spider) were selected for motion capture experiments. The method of multi-camera layout proposed in this report has flexible scalability. This method is valid for diverse small animals and it is potentially an effective basis for promoting the development of motion capture systems in other domains (such as the capture of objects with different shapes and sizes in the industrial field).