glStencilReplace

glStencilReplace is a function in the OpenGL graphics API. It is used to control the stencil buffer, which is a buffer used for various rendering effects such as shadowing, transparency, and anti-aliasing. Specifically, glStencilReplace sets a stencil buffer value to a specified reference value if a stencil test passes.

The function takes two arguments: a stencil buffer mask and a stencil buffer reference value. The mask is used to select which bits of the stencil buffer are to be modified, while the reference value is the new value that will be written to the selected bits.

When glStencilReplace is enabled, and the stencil test passes for a given pixel, the corresponding stencil buffer location is updated with the specified reference value. This allows for conditional modification of the stencil buffer based on the outcome of the stencil test. This is distinct from other stencil operations like glStencilOp, which might increment, decrement, or invert the stencil buffer value. glStencilReplace provides a direct way to overwrite the stencil buffer content.

This function is typically used in conjunction with other stencil buffer functions and configurations to achieve complex rendering scenarios. For example, it can be used to mark areas of the screen that have been rendered to, allowing subsequent rendering passes to selectively interact with those marked areas. It is part of the OpenGL Shading Language (GLSL) for programmable pipelines and also has a fixed-function equivalent in older OpenGL versions.