Harold

Introduction

Harold and the Purple Crayon is a 1955 children's book by Crockett Johnson. This is Johnson's most popular book. It led to a series of other books and inspired many adaptations. (Wikipedia: Harold and Purple Crayon) The comic book not only inspires the imagination of children but also spurs some non-photorealistic rendering research in the computer graphics field. One of the famous paper is "Harold: A World Made of Drawings" by Cohen, et al.

Purpose

Based on the description of the paper, I was tried to re-implement the software which is presented in the paper that mentioned. Moreover, understanding 3D mesh editing operations in response to user input is another goal of this project.

Design

The project has two different systems: land and sky. If the mesh is drawn on the land, it will follow the movement of land; if the mash is drawn on the sky, it will follow the motion of the sky. Therefore, with the help of ray selecting, I can decide the beginning and destination of the drawn mesh. Therefore, the drawn mesh can be classified into three categories: land-to-land, land-to-sky, and sky-to-sky. The land-to-land mesh will change the original land mesh; the land-to-sky mesh will build the new mesh to land; the sky-to-sky mesh will draw the new mesh on the sky.