The stencil bufferA memory store that holds an 8-bit per-pixel value. In Unity, you can use a stencil buffer to flag pixels, and then only render to pixels that pass the stencil operation. More info
See in Glossary stores an 8-bit integer value for each pixelThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
See in Glossary in the frame buffer. Before executing the fragment shaderA program that runs on the GPU. More info
See in Glossary for a given pixel, the GPU can compare the current value in the stencil buffer against a given reference value. This is called a stencil test. If the stencil test passes, the GPU performs the depth test. If the stencil test fails, the GPU skips the rest of the processing for that pixel. This means that you can use the stencil buffer as a mask to tell the GPU which pixels to draw, and which pixels to discard.
You would typically use the stencil buffer for special effects such as portals or mirrors. Additionally, the stencil buffer is sometimes used when rendering hard shadows, or constructive solid geometry (CSG).
You can use the Stencil
command to do two different things: to configure the stencil test, and to configure what the GPU writes to the stencil buffer. You can do both of these things in the same command, but the most common use case is to create one Shader objectAn instance of the Shader class, a Shader object is container for shader programs and GPU instructions, and information that tells Unity how to use them. Use them with materials to determine the appearance of your scene. More info
See in Glossary that masks out areas of the screen that other Shader objects cannot draw to. To do this, you need to configure the first Shader object to always pass the stencil test and write to the stencil buffer, and configure the others to perform a stencil test and not write to the stencil buffer.
Use the Ref
, ReadMask
, and Comp
parameters to configure the stencil test. Use the Ref
, WriteMask
, Pass
, Fail
, and ZFail
parameters to configure the stencil write operation.
This command makes a change to the render state. Use it in a Pass
block to set the render state for that Pass, or use it in a SubShader
block to set the render state for all Passes in that SubShader.
The stencil test equation is:
(ref & readMask) comparisonFunction (stencilBufferValue & readMask)
Shader "Examples/CommandExample" { SubShader { // The rest of the code that defines the SubShader goes here. Pass { // All pixels in this Pass will pass the stencil test and write a value of 2 to the stencil buffer // You would typically do this if you wanted to prevent subsequent shaders from drawing to this area of the render target or restrict them to render to this area only Stencil { Ref 2 Comp Always Pass Replace } // The rest of the code that defines the Pass goes here. } } }
This example code demonstrates the syntax for using this command in a SubShader block.
Shader "Examples/CommandExample" { SubShader { // All pixels in this SubShader pass the stencil test only if the current value of the stencil buffer is less than 2 // You would typically do this if you wanted to only draw to areas of the render target that were not "masked out" Stencil { Ref 2 Comp Less } // The rest of the code that defines the SubShader goes here. Pass { // The rest of the code that defines the Pass goes here. } } }
Did you find this page useful? Please give it a rating:
Thanks for rating this page!
What kind of problem would you like to report?
Thanks for letting us know! This page has been marked for review based on your feedback.
If you have time, you can provide more information to help us fix the problem faster.
Provide more information
You've told us this page needs code samples. If you'd like to help us further, you could provide a code sample, or tell us about what kind of code sample you'd like to see:
You've told us there are code samples on this page which don't work. If you know how to fix it, or have something better we could use instead, please let us know:
You've told us there is information missing from this page. Please tell us more about what's missing:
You've told us there is incorrect information on this page. If you know what we should change to make it correct, please tell us:
You've told us this page has unclear or confusing information. Please tell us more about what you found unclear or confusing, or let us know how we could make it clearer:
You've told us there is a spelling or grammar error on this page. Please tell us what's wrong:
You've told us this page has a problem. Please tell us more about what's wrong:
Thank you for helping to make the Unity documentation better!
Your feedback has been submitted as a ticket for our documentation team to review.
We are not able to reply to every ticket submitted.
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.