Codea supports the coder to write and run the OpenGL ES shader code on iPad directlly, it is very useful for designing 3D program, but the vars in shader can not be wathched directly, it makes the debug hardly. Because of this I try to make a tool function to show the value of var in shader outpu th screen, a proptype, it is simple, bad performance, but can work. With it we can watch the var in shader easily.

In fact, they are a few global vars and functions:

• Use for display the value of var showFloat()
• Use for generate the font ledRectChar()
• Use for judge the rect area inRect()

Copy the functions into the code of fragment shader, then run the showFloat() in main(), like below:

Positive int

shoufloat(float(2345));

Negative int

shoufloat(float(2345));

Float

shoufloat(.2345));

shoufloat(1234.345);

shoufloat(-1234.345);

shoufloat(.0);

• showFloat(float(-1234));

• showFloat(2097152.411);

• showFloat(2097152.11);

Articles record the whole development: from an idea to a available propotype

How to watch a var in shader? -A new solution: change the question from 'What is' to 'Is it'
How to watch a var in shader? -A new solution: change the question from 'What is' to 'Is it'

Codea 支持在 iPad 上直接编写 OpenGL ES 的 shader 程序, 对于设计 3D 程序而已非常方便, 但是 shader 内部的变量无法直接观察, 使得调试起来比较困难. 鉴于此, 试着写了一个可以把 shader 内部变量值输出到屏幕的工具, 类似原型的东西, 比较粗糙, 性能很差, 不过刚好能用, 利用它可以轻松地观察 shader 内变量的值.

实际上就是几个函数, 包括:

• 用于最终显示变量值的 showFloat()
• 用于生成所需字型的 ledRectChar()
• 用于判断矩形区域范围的 inRect()

把这几个函数的声明和实现拷贝到 fragment shader 的代码中, 直接在 main 函数中调用即可, 如下所示:

正整数

shoufloat(float(2345));

负整数

shoufloat(float(2345));

浮点数

shoufloat(.2345));

shoufloat(1234.345);

shoufloat(-1234.345);

shoufloat(.0);

记录完成这个原型工具的整个开发调试过程的思路

OpenGL ES 2.0 Shader 调试新思路(一): 改变提问方式
OpenGL ES 2.0 Shader 调试新思路(二): 做一个可用的原型