The Pressure Soft Body a Simple Model of Complex Behavior
Maciej Matyka · 2007
SIMPLE computational model of soft body animation in two and three dimensions is introduced. The model is based on fundamental principles: Newton’s Laws, Hookes Law and Ideal GasLaw. The simulated body consists of material points connected by springs. Additionally, pressure force on the body surface is applied. An equation of motion for each point is solved. The advantages of the model for educational applications are: it is based on fundamental physics laws; it is very fast and allows for an interactive simulation on home PC; its concept is simple enough to be understood by students. The model may be used as a representative example of physically based modelling in computer graphics and animation. Figure 1: The pressurized soft ball falling on the ground. The red lines indicate local velocity vectors of mass points building the shape of the object. 2. Spring-Mass model WE start from spring-mass model [1] that has beenwidely used in computer graphics and animation-mostly due to the simplicity and flexibility of its original form. Figure 2: The spring-mass model of cloth dynamics The spring-mass model contains mass particles connected by linear springs in both off- and diagonal directions (see figure 2). The Newton’s laws of motion give ordinary differ-ential equations describing dynamics of the model: d2~ri dt2 = ~Fi/mi, where mi is the i-th point mass, ~ri is it position and ~Fi =