Animation of a Grass Hopper

Introduction

A Grass Hopper has a more complex body and motions than a human. It has 6 legs, two of which are Jumping Legs and therefore special. It also has wings which assist it in its jumps. This document will explain how I was able to provide a good deal of the complex motion of a Grass Hopper with fairly minimal programming effort.

Methods

The most important methods used were to make the parts of the Grass Hopper modular as was explained in the document for the Human. From bottom up, the starting element is the Foot. For a Grass Hopper feet and legs are quite angular so this is a small rectangle that can rotate about an axis near its end (angle). The Foot is attached to a longer rectangle called a Walking Leg. The Walking Leg is also able to rotate about its top end to illustrate walking. The Jumping Leg has a Walking Leg attached to its rear. In addition, the Jumping Leg has a very muscular and long elliptical section which is usually almost horizontal, but can rotate about an axis near its front to poise for and implement jumping,

The Main Body of the Grass Hopper is a large ellipse that I call the Torso. The Jumping Leg is attached to and pivots about the center of the Torso. The front and middle Walking Legs are attached to the Torso near its bottom. The Wing is attached to the Torso slightly ahead of the Jumping Leg and can rotate about its attachment point. The head with its eye and antenna are also attached near the front of the Torso.

The animation provides two Exercises, Jump and Walk, which are programmed using the angles discussed above as well as whole body translations. The distance, height and speed of these exercises is determined by user-controlled Sliders. The programs to achieve these Exercises are made quite simple by use of the modular rotations discussed above.

For the case of the Jump, the Grass Hopper first poises for making the Jump. Then the actual Jump follows a parabolic path. The jump is initiated by a fast thrust of the Jumping Legs and is this is followed by flapping of the wings.

For the Walk, all walking legs rotate by small angles periodically and the whole body moves forward when the Feet move backwards. When the feet move forward, the body motion stops and the Walking Legs shorten so as not to drag on the ground.

The animation also includes a group of angle sliders that allow the viewer to change the angles of the Parts as well as the Composites so that the viewer can see how the composite rotations function.