EDUCATIVA DE LA REGIÓN CALLAO

Considering the group of users affected by rheumatoid arthritis, aged people, and children, it will be pertinent to know if these users can eat with the spoon without spilling the food. The collision detection algorithm, developed in this thesis is capable of handling collision of two or more deformable B-spline surfaces.

A B-spline surface patch having 8×8 control points net was used to represent food (jelly) for interaction with the spoon to mimic eating with a spoon. A 12×12×12 mass spring damper mesh was used to incorporate material properties of jelly to this model. Figure 7.14(a) shows the B-spline model and Figure 7.14 (b-c) show the mass spring mesh of this model.

(a) B-spline model (b) Mass spring model

shown with facets. The nodes are shown as green

dots

(c) Mass spring model. The thick red lines represent the boundries

of hexahedron mesh

Figure 7.14 (a) B-spline model representing food (jelly) (b-c) Mass spring mesh to incorporate material properties to the model.

The methodologies developed in this thesis, make it possible to model food (jelly) as a B-spline deformable model and simulate an environment in which a user can interact with food and spoon represented as B-spline surfaces. Figure 7.15(a) shows a spoon with a jelly on it, while the spoon was kept straight. Again, the collision detection algorithm detects the regions of the B-spline models colliding in the virtual reality environment.

(a) Jelly on spoon (b) Jelly starts flowing under its

own weight

(c) Jell stops flowing further due to its

own weight

(d) Other view of the jelly flowing due to

its own weight

Figure 7.15 Simulation of food (jelly) in a spoon without tilting it.

Due to its own weight, jelly started flowing downwards as shown in Figure 7.15(b). As soon as jelly deforms, the control points net of this B-spline model gets updated to represent deformed jelly. By using the blending matrices and the revised matrix of control points, points are once again generated on jelly. Spheres are generated on the jelly surface using these points. Same process is carried out for the spoon. The spheres generated on jelly and spoon are checked for intersection and more points and subsequently spheres are generated at the lower levels of detail. At the lowest level, the collision detection algorithm determines the nodes which will experience external force due to the collision. Thus the nodes of the mass spring mesh of jelly, which collide with spoon experience reactive force and do not move downwards. However, other nodes continue to move and their movements are determined by the mass spring mesh and the physical properties assigned to it. The control points of the B-spline models are updated and this process continues. As the mass spring model of spoon has more stiffness (given properties of steel), there is no noticeable change in the shape of spoon. However, if different material is chosen, the shape of spoon may also change.

As shown in Figure 7.15(b-d), jelly starts spilling out of the spoon. This means that if this design is used, the user cannot eat jelly by using this size without spilling it. Figure 7.15(d) shows the close up of the bowl of spoon. It is clear that the jelly is spilling from the front portion of the spoon bowl. At this point, an industrial designer can start modifying the design in such a way that the jelly does not get spilled. It is clear from Figure 7.15 (b-d) that the jelly was spilling from the front portion of the spoon bowl while the back portion was empty. The design of the spoon can be modified to see how the jelly will behave, if the bowl is tilted about 10 degree in the backward (clockwise for the spoon shown in Figure 7.15, when seen from the handle side along the handle) direction. Figure 7.16(a) shows the jelly put in a spoon with tilted bowl. The jelly starts flowing due to its own weight as shown in Figure 7.16(a-d). However, this time it does not spill out of the spoon as shown in Figure 7.16(d). It spreads in the spoon evenly. This shows that there was improvement in the design.

(a) Jelly on spoon (b) Jelly starts

flowing under its own weight

(c) Jell stops flowing further due to its

own weight

(d) Other view of the spoon. Jelly does not

spill out of spoon

Figure 7.16 Simulation of food (jelly) in a spoon when the bowl is tilted by ten degree.

The bowl was tilted by 20 degree to see if it further improves the design. However, as shown in Figure 7.17, the jelly started flowing from the back part of the spoon. This

means that by tilting the bowl by twenty degrees, the design deteriorated rather than improving its functionality.

(a) Jelly on spoon (b) Jelly starts

flowing under its own weight

(c) Jell stops flowing further due to its

own weight

(d) Bottom view of the spoon. Jelly spills out

of spoon

Figure 7.17 Simulation of food (jelly) in a spoon when the bowl is tilted by twenty degree.

The simulation suggests that the spoon bowl should be tilted by 10 degree to improve the design. In a similar fashion, other parameters of the spoon such as depth of the bowl, curvature of the bowl, or the width of the bowl, can be varied to determine best suitable design.

The industrial designer can also determine weight of the spoon, the deflection of the spoon due to its own weight and that of the food, while using different materials for the spoon. The preliminary evaluation of the concepts in the virtual reality environment would help the industrial designer to come up with the designs which can be successfully implemented. The tools developed in this thesis, can provide this environment to the industrial designer.