Free Fall Motion Synthesis

彬彬

Abstract

We present in this paper a framework that generates free fall motions

for the object within a still fluid. We introduce a new motion

synthesis approach where six characteristic motion prototypes of

free fall are defined and synthesized, and then the motion trajectory

is specified form free fall motion graph. We automatically create

motion sequences using trajectory search tree and pre-computed

trajectory database. The proposed approach can produce realistic

and controllable free fall motion that could be applied in many different

applications, including virtual reality, game and other entertainment

productions.

CR Categories: I.2.7 [Articial Intelligence]: Problem Solving,

Control Methods and Search—Graph and tree search strategies;

I.3.7 [Computer Graphics]: Three-Dimensional Graphics and

Realism—Animation;

Keywords: physically based animation, motion prototypes, free

fall

1 Introduction

It is difficult to simulate the common and spectacular free falling

motions around us in computer graphics (e.g., paper, leaves, and

snowflakes within air). Our main purpose is to extract the physical

rules behind the phenomena and archive realistic simulation results.

Most motion generations of free fall are example-based approaches.

They synthesized the motion trajectories from captured video, simple

fluid simulation, commercial 3D animation software, or sketch

example. All these approaches ignored the nature of free fall and

considered the free fall as complex and unpredictable process using

complete stochastic model or simple particle representation in flow.

As the another approach, physicist recently focused on the unsteady

dynamic of free falling through thousands of experiments and this

remains a significant challenge [Razavi 2010].

In this work, we propose new approach combining both experimental

and theoretical results. About the free fall in computer graphics,

our primary focus examines all the motion types of light-weight

objects to create reliable and natural motion paths by using motion

planning in real time environment.

2 Motion Generation

Our method (Figure 1) uses the initial conditions and physical parameters

of a light-weight object with 6 degree of freedoms as inputs,

including the physical characteristics of the object and fluid

wherein released (release height, mass, etc.). We transform the parameters

to two important non-dimensional numbers Re and I,

and then lookup the phase diagram (Figure 1) of free fall to query

the main motion prototype which is the stable status for the falling

object.

After the main motion prototype is decided, we first determine the

motion types based on motion groups. For all motion types of the

decided motion type, our probability model is adopted to choose

the actual motion paths. In our work, the motion trajectory is constructed

from six motion sequences of motion prototypes. The free

fall motion graphs are used to synthesize the trajectories from the

designated motion segments. The final free fall motions are synthesized

after the initial trajectories are determined through optimization.

彬彬

菜刀吻电线

爱咋咋地！

菜刀吻电线

很经典，很实用，学习了!

晃晃

我无语！

奇

路过、路过、快到鸟，列位请继续...ing

菜刀吻电线

不错哦,顶一下......

晃晃

很经典，很实用，学习了!

tc

谢谢楼主，真是太实用了

奇

呵呵,真得不错哦!!