| VertexData |
The VertexData class manages a raw list of vertex information, allowing direct upload to OpenGL vertex buffers. _You only have to work with this class if you create display objects with a custom render function. If you don't plan to do that, you can safely ignore it._ To render objects with OpenGL, you have to organize vertex data in so-called vertex buffers. Those buffers reside in graphics memory and can be accessed very efficiently by the GPU. Before you can move data into vertex buffers, you have to set it up in conventional memory - that is, in a byte array. That array contains all vertex information (the coordinates, color, and texture coordinates) - one vertex after the other. To simplify creating and working with such a bulky list, the VertexData class was created. It contains methods to specify and modify vertex data. The raw array managed by the class can then easily be uploaded to a vertex buffer. **Premultiplied Alpha** The color values of texture files may contain premultiplied alpha values, which means that the 'RGB' values were multiplied with the 'alpha' value before saving them. On rendering, it makes a difference in which way the alpha value is saved; for that reason, the VertexData class mimics this behavior. You can choose how the alpha values should be handled via the 'premultipliedAlpha' property. |