May 2010
Intermediate to advanced
438 pages
11h 28m
English
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Chapter 7. Sprites and Text
My god, it’s full of stars.
—Dave Bowman, 2001: A Space
Odyssey
Even though OpenGL ES is designed for 3D graphics, you’ll often find the need to render visual elements that are 2D. OpenGL is actually quite well-suited to rendering a flat world; several popular 2D libraries, such as cocos2d, use OpenGL as their rendering engines.
The most common type of 2D rendering is text rendering. The OpenGL API lives too close to the metal to treat text as a first-class citizen, but it’s easy to render a pregenerated glyph (a character’s shape in a given font) using a textured quad, and that’s the approach we’ll take in this chapter.
Note
Computing the points along the outline of a
glyph can be surprisingly complex. For example, the TrueType file format
specifies a unique programming language—complete with loops and
if statements—solely for the purpose of tweaking the
curves in a glyph.
In this chapter, we won’t attempt to go over kerning algorithms, ligatures, or line wrapping; simple text layout is good enough for our purposes. (Check out the popular pango library if you need a full-featured layout engine.)
Another common 2D concept is the sprite, which is a rather generic term for any bitmap that gets composited into a scene. Sprites often contain transparent regions, so their texture format contains alpha. Sprites are often animated in some way. There are two ways of animating a sprite: its screen position can change (imagine a bouncing ball), or its source image can ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.