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r00ster 2019-01-14 15:22:32 +01:00 committed by GitHub
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@ -18,7 +18,7 @@ Although these simple lines of code don't look like a lot, we can infer substant
4. If we look closely to the `vec4` type we can infer that the four arguments respond to the RED, GREEN, BLUE and ALPHA channels. Also we can see that these values are *normalized*, which means they go from `0.0` to `1.0`. Later, we will learn how normalizing values makes it easier to *map* values between variables.
5. Another important *C feature* we can see in this example is the presence of preprocessor macros. Macros are part of a pre-compilation step. With them it is possible to `#define` global variables and do some basic conditional operation (with `#ifdef` and `#endif`). All the macro comands begin with a hashtag (`#`). Pre-compilation happens right before compiling and copies all the calls to `#defines` and check `#ifdef` (is defined) and `#ifndef` (is not defined) conditionals. In our "hello world!" example above, we only insert the line 2 if `GL_ES` is defined, which mostly happens when the code is compiled on mobile devices and browsers.
5. Another important *C feature* we can see in this example is the presence of preprocessor macros. Macros are part of a pre-compilation step. With them it is possible to `#define` global variables and do some basic conditional operation (with `#ifdef` and `#endif`). All the macro commands begin with a hashtag (`#`). Pre-compilation happens right before compiling and copies all the calls to `#defines` and check `#ifdef` (is defined) and `#ifndef` (is not defined) conditionals. In our "hello world!" example above, we only insert the line 2 if `GL_ES` is defined, which mostly happens when the code is compiled on mobile devices and browsers.
6. Float types are vital in shaders, so the level of *precision* is crucial. Lower precision means faster rendering, but at the cost of quality. You can be picky and specify the precision of each variable that uses floating point. In the first line (`precision mediump float;`) we are setting all floats to medium precision. But we can choose to set them to low (`precision lowp float;`) or high (`precision highp float;`).