<function name="SetStencilFailOperation" parent="render" type="libraryfunc"> <description> Sets the operation to be performed on the stencil buffer values if the compare function was not successful. Note that this takes place **before** depth testing. </description> <realm>Client</realm> <args> <arg name="failOperation" type="number">Fail operation function, see <page>Enums/STENCILOPERATION</page></arg>⤶ <arg name="failOperation" type="number">Fail operation function, see <page>Enums/STENCILOPERATION</page>.</arg>⤶ </args> </function> <example> <description> This is one of the most useful things stencils can do - not render something to the screen and then allow you to draw with the shape it would have been if it `had` rendered. This is one of the most useful things stencils can do - not render something to the screen and then allow you to draw with the shape it would have been if it **had** rendered. You can see in the output screenshot that a partially obscured entity will still write its entire shape to the stencil buffer. ⤶ From [Lex's Stencil Tutorial](https://github.com/Lexicality/stencil-tutorial).⤶ </description> <code> hook.Add( "PostDrawOpaqueRenderables", "Stencil Tutorial Example", function() ⤶ -- Reset everything to known good -- Reset everything to known good render.SetStencilWriteMask( 0xFF ) render.SetStencilTestMask( 0xFF ) render.SetStencilReferenceValue( 0 ) -- render.SetStencilCompareFunction( STENCIL_ALWAYS ) render.SetStencilCompareFunction( STENCIL_ALWAYS ) render.SetStencilPassOperation( STENCIL_KEEP ) -- render.SetStencilFailOperation( STENCIL_KEEP ) render.SetStencilFailOperation( STENCIL_KEEP ) render.SetStencilZFailOperation( STENCIL_KEEP ) render.ClearStencil() -- Enable stencils render.SetStencilEnable( true ) -- Set the reference value to 1. This is what the compare function tests against render.SetStencilReferenceValue( 1 ) -- Only draw things if their pixels are currently 1. Currently this is nothing. render.SetStencilCompareFunction( STENCIL_EQUAL ) -- If something fails to draw to the screen, set the pixels it would have drawn to 1 -- This includes if it's behind something. render.SetStencilFailOperation( STENCIL_REPLACE ) -- Draw our entities. They will not draw, because everything is 0 for i, ent in ipairs( ents.FindByClass( "sent_stencil_test" ) ) do for _, ent in ipairs( ents.FindByClass( "prop_physics" ) ) do ent:DrawModel() end -- If we were to re-draw our entities, we'd see them, but otherwise they're invisible. -- If we flush the screen, we can show the "holes" they've left in the stencil buffer render.ClearBuffersObeyStencil(0, 148, 133, 255, false); render.ClearBuffersObeyStencil( 0, 148, 133, 255, false ) -- Let everything render normally again render.SetStencilEnable( false ) end ) </code> <output><image src="basic_fail_operation.jpg" alt="800px"/></output> ⤶ </example></example>