Development of Model and Software for Tracking Head Avatars in E-Learning Systems

Introduction

Our chapter uses computer graphics terminology. These terms are known, but, unfortunately, many authors observed differences in their interpretation and interpretation. Therefore, the following provides a brief description of the terminology used with computer graphics.

Vector Graphics uses the term ‘vectors’. For example, you can set the line pair of vectors - coordinates of the start and end points. Vector images are easily modified (moved, rotated, scaled, etc.) using the transformation vectors. If the vector belongs to three-dimensional space, we speak about of three-dimensional (3D) graphics, if the two-dimensional - a 2D graph. In raster graphics image is a two-dimensional array consisting of discrete elements (pixels) also called pixels. The bitmap can contain a different set of colors, for example, 256 shades of gray or palette containing several million colors. If the image contains shades of gray, then the value of the pixel of the image is called its intensity. The intensity of the pixel – a scalar value is an integer ranging from 0 to 255. For images that contain a rich color palette, we do not speak about the intensity of the pixel values. Color being asked is a set of three components RGB. Each color component - a scalar, are integers ranging from 0 to 255 and can convert a color image into RGB grayscale-image, however, reverse conversion (grayscale in RGB) is not possible. Vectors can be translated into a bitmap, this process is called rasterization. In the course of many years of work of various researchers in the field of computer graphics, they developed a standard called specification OpenGL. Standard Library Computer Graphics OpenGL - a software interface to graphics hardware, allows you to set the objects and operations involved in the production of high-quality graphics. OpenGL is keen to work with 3D and 2D vector graphics that after rasterization can be displayed on the screen of the user. We emphasize that the OpenGL is only a specification, a set of rules that must be followed by implementation. For example, different implementations may use different OpenGL algorithm to rasterize the primitives and differ in other respects. OpenGL specification clearly indicates the set of properties that are invariant to any implementation. In the field of computer vision that gradually acquired its own standard – there is computer vision library OpenCV. This is a collection of functions written in C, realizing many popular algorithms for image processing and computer vision algorithms (Mkrttchian, 2011).

The head of the person / avatar as a three-dimensional object (Figure 1 a), in 3D computer graphics can be represented as a model that defines the geometric shape and texture of the object (Figure 1, b, c). The geometric shape of the object model can be approximated by a set of primitive geometric shapes. OpenGL allows various primitive shapes (Figure 1, d), such as triangles, the sequence of triangles, quadrangles flat, flat polygons. Top of the three-dimensional coordinates are assigned, specifying its position in three-dimensional space. As mentioned earlier, the value of the vertex color is determined by three components of RGB.

Figure 1.

Head modeling, a) – 3D objeject – head, b) The model of the object and the associated object coordinate system (RMS), c) The textures applied to the surface of the object model, and the coordinate system of the texture, d) Primitive figures. The arrows show the direction of traversal of vertices clockwise.

Important task sequence of vertices of the primitive (direction of rotation), since it depends on the appearance of primitive shapes. It is believed that if projected onto the plane of the vertices of the frame traversal order of the vertices clockwise, the primitive see otherwise - invisible. Top of the figure can be assigned two-dimensional texture coordinates that define the corresponding point on the top of a two-dimensional texture. To set the vertex texture coordinates, is use the command glTexCoord2d (Mkrttchian, 2012).

Background

We present an algorithm for constructing a texture for the model of the head: