NeHe OpenGL Lesson15 – Texture Mapped Outline Fonts

This sample program shows us how to texture mapping outline fonts.
It seems the outline fonts does not generate 3d font object texture coordinates for us. And luckily, OpenGL provide some interfaces that let us create the texture coordinates on fly.
Is the skull show on the left like a font? Here the sample did not use the standard font, a SYMBOLfont named windings fonts. You have to tell Windows that the font is a symbol font and not a standard character font. For more details, you need to check the create font part about how such font be created. Or you will get better understand if you do a compare with tutorial 14 ones. 

To create the texture coordinates on fly in OpenGL, the code write like this:

glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);
glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);

 

As you will see from the left image, you will understand what GL_S and GL_T refer for? What the above code do just set the way how texture coordinates will be created and enable them. Some default parameters  used, so you will not see them. You could read glTexGeni function further, you will get more options that could be used to control how those coordinates should be generated, some additional parameters that we could set.

 

The full source code could be downloaded from here.

转载于:https://www.cnblogs.com/open-coder/archive/2012/08/23/2653339.html