What are the best practices for writing shader code?

1 Use variables wisely

Variables are the basic building blocks of shader code, as they store and manipulate data. To prevent slowing down your shader and consuming more memory, you should use constants for values that never change, such as pi, colors, or thresholds. Uniforms should be used for values that are the same for all pixels, such as time, camera position, or light direction. Varyings should be used for values that are interpolated between vertices, such as texture coordinates, normals, or colors. Additionally, local variables should be used for values that are only used within a function or a scope; they should also be declared as close as possible to where they are used. Lastly, descriptive and consistent names should be given to your variables to avoid using reserved keywords or built-in variables.

2 Write modular and reusable functions

Functions are a great way to organize and reuse shader code, as they are used to perform a specific task and return a value. Writing modular and reusable functions can make shader code more readable, maintainable, and efficient. To do this, you should write functions that have a clear and single purpose, such as calculating lighting or blending colors. Additionally, the input and output should be consistent; for example, taking a vector and returning a scalar. Functions should also be independent and self-contained, avoiding the use of global variables, uniforms, or varyings. Furthermore, they should be generic and flexible enough to handle different types of data. Finally, make sure that functions are well-documented and commented to explain what they do, what they expect, and what they return.

3 Use loops and conditional statements carefully

Loops and conditional statements are a way of controlling the flow of your shader code, as they execute a block of code repeatedly or conditionally. In order to add complexity and functionality to your shader without causing performance issues or bugs, it is important to use loops and conditional statements sparingly and with caution. For loops should have a fixed or known number of iterations, such as those that use a constant or a uniform as the limit, or unroll loops with a macro or pragma directive to expand the code at compile time. Conditional statements should also be used wisely and with moderation, as they can cause your shader to branch and diverge. If statements should depend on a uniform or constant, while switch statements should have few cases. Alternatively, mathematical or logical expressions such as min, max, clamp, abs, sign, or step can be used to avoid branching.

4 Debug and optimize your shaders

Debugging and optimizing your shaders are essential steps to ensure that your shader code works correctly and efficiently. Debugging refers to finding and fixing errors or bugs in the shader code, such as syntax, logic, or runtime errors. Optimizing, on the other hand, is about improving the performance or quality of the shader code through reducing instructions, memory accesses, or texture samples. To debug and optimize your shaders, you should use some tools and techniques like a shader editor or an IDE with syntax highlighting, error checking, code completion, and debugging features. Additionally, a shader profiler or debugger can measure and analyze execution time, memory usage, and output of your shader code. Moreover, a shader validator or compiler can check and report the validity, compatibility, and optimization of your shader code. Finally, debugging and optimization techniques like adding debug colors or using texture compression can help you identify and solve problems in your shader code.

5 Avoid common pitfalls and errors

Writing shader code can be tricky and error-prone, so it's important to be aware of common pitfalls and errors. For example, precision issues may affect the accuracy and quality of your shader output, so you should use the appropriate precision qualifier for your variables, such as lowp, mediump, or highp. Additionally, you should avoid using floating-point values that are too small or too large as they can cause underflow or overflow errors. When it comes to swizzling, you should use it carefully and consistently, and avoid using swizzling that is invalid or ambiguous. As for sampling, make sure to use it correctly and efficiently, avoiding invalid or unnecessary sampling. Furthermore, you should also avoid using redundant or expensive sampling such as using a texture that is too large or too detailed.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?