How does Open GL works?

Answer 1

OpenGL bases on the state variables. There are many values, for example the color, that remain after being specified. That means, you can specify a color once and draw several polygons, lines or what ever with this color then. There are no classes like in DirectX. However, it is logically structured. Before we come to the commands themselves, here is another thing:

To be hardware independent, OpenGL provides its own data types. They all begin with "GL". For example GLfloat, GLint and so on. There are also many symbolic constants, they all begin with "GL_", like GL_POINTS, GL_POLYGON. Finally the commands have the prefix "gl" like glVertex3f(). There is a utility library called GLU, here the prefixes are "GLU_" and "glu". GLUT commands begin with "glut", it is the same for every library. You want to know which libraries coexist with the ones called before? There are libraries for every system, Windows has the wgl*-Functions, Unix systems glx* and so on

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A very important thing is to know, that there are two important matrices, which affect the transformation from the 3d-world to the 2d-screen: The projection matrix and the modelview matrix. The projection matrix contains information, how a vertex - let's say a "point" in space - shall be mapped to the screen. This contains, whether the projection shall be isometric or from a perspective, how wide the field of view is and so on. Into the other matrix you put information, how the objects are moved, where the viewer is and so on

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Don't like matrices? Don't be afraid, you probably won't really see them, at least at the beginning. There are commands that do all the maths for you.