Branching is one way of introducing conditional behavior into shaderA program that runs on the GPU. More info
See in Glossary code.
This page contains information on the following techniques:
For a general overview of conditionals in shader code and when to use which technique, see Conditionals in shader code.
When a shader program includes conditionals that are evaluated at compile time, it uses static branching. The compiler excludes the code from the unused branch, so it does not appear in the compiled shader program.
Internally, Unity uses static branching when it creates shader variants; however, static branching on its own does not have any of the performance disadvantages of shader variants.
The main advantage of static branching is that it has no negative impact on runtime performance. The main disadvantage of static branching is that you can only use it at compile time.
Static branching means that the compiler excludes unneeded code from the shader program. It results in small, specialized shader programs that contain only the necessary code. There is no runtime performance cost to static branching; in fact, the smaller programs are likely to result in quicker load times and lower runtime memory usage.
To use static branching, the conditions must be constant at compile time. This means that you can’t use it to execute code for different conditions at runtime.
You can use static branching in your shaders in the following ways:
if
statements can also be used for dynamic branches, the compiler detects the compile-time constant value and creates a static branch instead.Note: Static branching is available only in hand-coded shaders. You cannot create static branches in Shader Graph.
When a shader program includes conditionals that are evaluated at runtime, it uses dynamic branching.
There are two types of dynamic branching: dynamic branching based on uniform variables, and dynamic branching based on any other runtime value. Uniform-based branching is usually more efficient, because the uniform value is constant for the whole draw call.
The main advantage of dynamic branching is that it allows you to use conditionals at runtime without increasing the number of shader variants in your project. The main disadvantage of dynamic branching is that it impacts GPU performance.
The GPU performance impact varies by hardware, and by shader code. The reasons are:
In general, if your code branches on uniform values and both branches have roughly similar workloads, then the impact on GPU performance is likely to be small. However, you should always profile your application and consider the advantages and disadvantages case-by-case.
Note: Dynamic branching can also lead to large shader programs, because the code for all conditions is compiled into the same shader program. However, the effect of these larger files on load times and memory usage is usually less significant than the impact of shader variants.
For information about other ways of using conditionals in shaders, and how to decide which technique is right for your use case, see Conditionals in shaders.
You can use dynamic branching in your shaders in the following ways:
When you visit any website, it may store or retrieve information on your browser, mostly in the form of cookies. This information might be about you, your preferences or your device and is mostly used to make the site work as you expect it to. The information does not usually directly identify you, but it can give you a more personalized web experience. Because we respect your right to privacy, you can choose not to allow some types of cookies. Click on the different category headings to find out more and change our default settings. However, blocking some types of cookies may impact your experience of the site and the services we are able to offer.
More information
These cookies enable the website to provide enhanced functionality and personalisation. They may be set by us or by third party providers whose services we have added to our pages. If you do not allow these cookies then some or all of these services may not function properly.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
These cookies may be set through our site by our advertising partners. They may be used by those companies to build a profile of your interests and show you relevant adverts on other sites. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. If you do not allow these cookies, you will experience less targeted advertising. Some 3rd party video providers do not allow video views without targeting cookies. If you are experiencing difficulty viewing a video, you will need to set your cookie preferences for targeting to yes if you wish to view videos from these providers. Unity does not control this.
These cookies are necessary for the website to function and cannot be switched off in our systems. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. These cookies do not store any personally identifiable information.