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Stencil buffer
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<p>A <a href="/facts/Stencil/EN96ffRd">stencil</a> buffer is an extra <a href="/facts/Data_buffer/tVy4j2Dc">data buffer</a>, in addition to the <i>color buffer</i> and <i><a href="/facts/Z-buffering/HTyzcKbx">Z-buffer</a></i>, found on modern <a href="/facts/Graphics_hardware/ngNe2nDc">graphics hardware</a>. The buffer is per pixel and works on <a href="/facts/Integer/PUwwrawx">integer</a> values, usually with a depth of one <a href="/facts/Byte/BNHUp9Qq">byte</a> per pixel. The <a href="/facts/Z-buffering/HTyzcKbx">Z-buffer</a> and stencil buffer often share the same area in the <a href="/facts/Random_access_memory/DuD4bxh6">RAM</a> of the graphics hardware. </p><p>In the simplest case, the stencil buffer is used to limit the area of <a href="/facts/Rendering_(computer_graphics)/YYxfnmAq">rendering</a> (stenciling). More advanced usage of the stencil buffer makes use of the strong connection between the Z-buffer and the stencil buffer in the <a href="/facts/Graphics_pipeline/XnF55m31">rendering pipeline</a>. For example, stencil values can be automatically increased/decreased for every pixel that fails or passes the depth test. </p><p>The simple combination of depth test and stencil modifiers make a vast number of effects possible (such as stencil <a href="/facts/Shadow/f9zpBgFQ">shadow</a> volumes, Two-Sided Stencil, compositing, decaling, dissolves, fades, swipes, silhouettes, outline drawing, or highlighting of intersections between complex <a href="/facts/Geometric_primitive/FmpXkhao">primitives</a>) though they often require several rendering passes and, therefore, can put a heavy load on the graphics hardware. </p><p>The most typical application is still to add shadows to <a href="/facts/3D_computer_graphics/zlWW6eaF">3D applications</a>. It is also used for planar reflections. </p><p>Other rendering techniques, such as <a href="/facts/Portal_rendering/B2rGDC0s">portal rendering</a>, use the stencil buffer in other ways; for example, it can be used to find the area of the screen obscured by a portal and re-render those pixels correctly. </p><p>The stencil buffer and its modifiers can be accessed in computer graphics by using <a href="/facts/Application_programming_interface/GMlN4vUr">APIs</a> like <a href="/facts/OpenGL/xQoMWePr">OpenGL</a>, <a href="/facts/Direct3D/WHJ6DTcv">Direct3D</a>, <a href="/facts/Vulkan_(API)/e188Vdpc">Vulkan</a> or <a href="/facts/Metal_(API)/DIbAxKF6">Metal</a>. </p>