depthStencil

DepthStencil, in computer graphics, refers to a depth-stencil buffer used by the rendering pipeline to control visibility and masking of fragments. The depth component stores, per pixel, the distance from the viewer to the closest surface (z-value) to enable depth testing. The stencil component holds a per-pixel value used to mask rendering operations and drive multi-pass effects, such as mirrors, shadows, outlines, and complex clipping.

Depth-stencil buffers are created as a resource with a depth-stencil format. Common formats include dense depth with an accompanying stencil bit, such as 24-bit depth with 8-bit stencil (D24S8) or 32-bit depth (D32) with optional stencil. In many APIs, the depth data and stencil data are stored in a single buffer, with separate views or state controlling how they are accessed. The depth aspect is typically written by the pipeline during depth testing, while the stencil aspect is updated through stencil operations.

During rendering, the pipeline can perform a depth test using a comparison function (for example, less-than or less-or-equal) and may write depth values to the buffer. If stencil testing is enabled, a per-pixel stencil test is performed against a reference value, and stencil operations specify how to modify the stencil value when tests pass or fail (e.g., keep, zero, replace, increment, decrement, invert). Two-sided stencil testing can apply different operations for front-facing and back-facing polygons.

Depth-stencil resources are bound as depth-stencil targets and may be cleared at the start of a pass. Depth-stencil state objects control whether depth and stencil tests are enabled, their comparison functions, and write masks. Proper use of depth and stencil testing is essential for correct occlusion, masking, and many post-processing effects, while also impacting rendering performance and memory usage.