FragStencilRefEXT

FragStencilRefEXT

Decorating a variable with the FragStencilRefEXT built-in decoration will make that variable contain the new stencil reference value for all samples covered by the fragment. This value will be used as the stencil reference value used in stencil testing.

To write to FragStencilRefEXT, a shader must declare the StencilRefReplacingEXT execution mode. If a shader declares the StencilRefReplacingEXT execution mode and there is an execution path through the shader that does not set FragStencilRefEXT, then the fragment’s stencil reference value is undefined: for executions of the shader that take that path.

Only the least significant s bits of the integer value of the variable decorated with FragStencilRefEXT are considered for stencil testing, where s is the number of bits in the stencil framebuffer attachment, and higher order bits are discarded.

See fragment shader stencil reference replacement for more details.