Falling Water with Key Particle and Envelope Surface
for Virtual Liquid Manipulation Model
Shunsuke Miyashita

Kenji Funahashi

Nagoya Institute of Technology
Gokiso-cho, showa-ku, Nagoya 466-8555 Japan

Nagoya Institute of Technology
Gokiso-cho, showa-ku, Nagoya 466-8555 Japanmiyasita@center.nitech.ac.jp

Kenji@nitech.ac.jp

Categories and Subject Descriptors
H.5.1 [Information Interfaces and Presentation]: Multimedia Information Systems—Artiﬁcial, augmented, and virtual realities

Author Keywords
liquid manipulation model; key particle; envelope surface

1. INTRODUCTION
We have proposed a liquid manipulation model based onparticle and volume, and a VR chemical laboratory system [1]. In the CG ﬁeld, although researchers usually use
particle method to simulate realistic ﬂuid, it needs enormous
computation time and usually needs parallel processing torealize real-time simulation [2]. One of our main goal is toprovide the VR-learning system for the people, i.e., who haveto stay in the hospital. Therefore we have already proposed
an interactive model of virtual liquid like water which focus on user impression and real-time processing rather thanexact behavior simulation. The model can make user feel
realistic sensation from the water behavior manipulated byuser’s container. However free fall water was simulated andrendered with particles simply. The processing speed is inﬂuenced by a lot of particles, and CG quality is insuﬃcient.
In this paper, we propose an eﬃcient and eﬀective methodof free fall water with key particles instead of conventional
particles. The envelope surface is rendered around the key
particles as a surface of the water. The new model can makemore realistic sensation with higher processing speed.

Figure 1: Experimental system
as just particles and rendered as simple square transparent
polygons. Using this model, an interactive water manipulation is realized in real-time.

3.

KEY PARTICLE BASED MODELIn our new model, key particles are proposed to represent
falling water behavior. They have their own location, volume and color parameters, and do not interfere each other assame as conventional particles. While water is ﬂowing, key
particles are generated at regular intervals, then each particle moves according to gravity and inertia. So the numberof key particles is less than the conventional ones. When theﬂow is stopped, the particle segment is separated. Finally,
envelope surfaces are rendered around each segment of thekey particles. The surface is constructed as a frustum foreach pair of adjoining key particles, base area is decided by
the volume parameter of the particle.

2. VOLUME & PARTICLE BASED MODEL4.

We usually manipulate water with container, and count it
as “a cup of water.” So we represent the water in our proposed model as following two conditions to simplify calculation; the stay condition which exists in a container and thefree fall condition which ﬂows from/to container. The former is treated with volume value, and the latter is treated asa simple particle system that particles do not interfere eachother. Although water is not one object, we treat the water in a container as one object, and calculate water surface
level from volume and its tilt. We have also developed themethod to express wave, vortex and color diﬀusion on thesurface. However the free fall condition water is represented

We proposed the new model which represents falling liquid with key particles and an envelope surface as a part ofthe virtual liquid manipulation model. It can make more realistic sensation with higher speed (Fig. 1). As a future work,
we should implement a VR chemical laboratory system ona mobile computer, and evaluate its validity from students.
Acknowledgments: This work was supported in part by
JSPS KAKENHI Grant Number 24501186.

Copyright is held by the author/owner(s).
VRST’12, December 10–12, 2012, Toronto, Ontario, Canada.
ACM 978-1-4503-1469-5/12/12.

5.

CONCLUSIONSREFERENCES[1] Natsume, et al. The virtual chemical laboratory using
particle and volume based liquid model. Proc. SCIS &ISIS, 1354–1359, 2010.
[2] Losasso, et al. Two-way coupled SPH and particle levelset ﬂuid simulation. IEEE TVCG, 14(4):797–804, 2008.