Wallace Santos Lages

Boids that see: Using self-occlusion for simulating large groups on GPUs

Behavioral models have been used in the entertainment industry to increase the realism in the simulation of large groups of individuals. Unfortunately, the classical models can be very compute-intensive when very large groups are considered, reducing its applicability in games and other interactive systems. In this article we explore both search space reduction and parallelism to improve the performance of Reynolds Boids model. We propose a methodology that considers self-occlusion (visibility culling) to reduce the number of neighbors and we take advantage the parallelism present in common graphics processor units (GPUs) to allow the simulation of very large groups. We performed different GPU implementations (GPGPU and CUDA); the results show that visibility culling allows significant gains in performance without affecting the models overall behavior.

A Parallel Multi-view Rendering Architecture

We present an architecture for rendering multiple views efficiently on a cluster of GPUs. The original scene is sampled by virtual cameras which are used later to reconstruct the desired views. We show that this image-based approach can be very scalable and support rendering at interactive rates.

Performance analysis of a parallel multi-view rendering architecture using light fields

Multiple view rendering is a common problem for applications where multiple users visualize a common dataset, as in multi-player games and collaborative engineering tools. For a system to be able to render a large number of views at interactive rates efficiently, parallel processing is an attractive technique. In this work, we present the implementation of a pipelined multiview light field renderer using a cluster with GPUs and MPI. We discuss the parallelization model and the problem of partitioning the tasks of the pipeline among the cluster machines based on the pipeline model and the costs of the stages. Our solution achieves 83% efficiency with ten machines, against only 11% efficiency of a naive parallelization.

Move the Object or Move Myself? Walking vs. Manipulation for the Examination of 3D Scientific Data

Physical walking is consistently considered a natural and intuitive way to acquire viewpoints in a virtual environment. However, research findings also show that walking requires cognitive resources. To understand how this tradeoff affects the interaction design for virtual environments; we evaluated the performance of 32 participants, ranging from 18 to 44 years old, in a demanding visual and spatial task. Participants wearing a virtual reality (VR) headset counted features in a complex 3D structure while walking or while using a 3D interaction technique for manipulation. Our results indicate that the relative performance of the interfaces depends on the spatial ability and game experience of the participants. Participants with previous game experience but low spatial ability performed better using the manipulation technique. However, walking enabled higher performance for participants with high spatial ability or without significant game experience. These findings suggest that the optimal design choices for demanding visual tasks in VR should consider both controller experience and the spatial ability of the target users.

Bookshelf and Bird: Enabling real walking in large VR spaces

We present two novel redirection techniques to enable real walking in large virtual environments (VEs) using only “room-scale” tracked spaces. The techniques, called Bookshelf and Bird, provide narrative-consistent redirection to keep the user inside the physical space, and require the user to walk to explore the VE. The underlying concept, called cell-based redirection, is to divide the virtual world into discrete cells that have the same size as the physical tracking space. The techniques then can redirect the users without altering the relationship between the user, the physical space, and the virtual cell. In this way, users can always access the entire cell using real walking.

Structural Coupling on Creative Interfaces

We describe how self-production systems theory can be applied in the design of new creative interfaces. By modeling the interface as an organizationally closed system, we can support creative agency while still allowing collaboration with the user. Although in this approach the interactor no longer solely determines the output, both the user and interface can become structurally coupled, achieving a balanced interaction. We discuss our theoretical motivations and describe an initial attempt in the domain of human-machine collaborative painting.

Better Hands

Better Hands (2017) is an interactive installation that explores the limits and the role of tools in the creative process. It questions the nature of authorship by bringing the interface closer to the body, while empowering it with embedded agency. The artwork invites us to reflect on the effect of modern technology on the basic act of creation and whether we control or are defined by it.

Ray, camera, action! A technique for collaborative 3D manipulation

We present a technique to support collaborative 3D manipulation. Our approach is based on two or more users jointly specifying the parameters of each transformation using a point, a ray, and a scalar value. We discuss how this concept can be coupled with a camera system to create a scalable technique that can accommodate both parallel and serial collaboration.

Designing capsule, an input device to support the manipulation of biological datasets

In this paper we present the design process of Capsule, an inertial input device to support 3D manipulation of biological datasets. Our motivation is to improve the scientists workflow during the analysis of 3D biological data such as proteins, CT scans or neuron fibers. We discuss the design process and possibilities for this device.

Effects of field of regard and stereoscopy and the validity of MR simulation for visual analysis of scientific data

We report the findings of a study designed to evaluate the effect of stereopsis and field of regard (FOR) in two different mixed reality (MR) simulation platforms: a head-mounted display (HMD) and a CAVE. We compared the performance of participants on two levels of stereopsis (mono and stereo) and two levels of FOR (90 degrees and 270 degrees) using a variety of scientific visualization tasks. Among the findings, we observed that not all the effects were consistent between the platforms. Stereo alone or in combination with higher FOR improved completion time on both platforms. However, adding stereo solely reduced the accuracy of the participants on the CAVE and improved on the HMD. Our findings extend prior knowledge on the contribution of visual fidelity components and suggests potential limits on MR simulation between platforms.