<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.⤶ Sets the <page text="Stencil Operation">Enums/STENCILOPERATION</page> that will be performed on the Stencil Buffer values of pixels affected by draw operations if the <page text="Compare Function">render.SetStencilCompareFunction</page> did **not** <page text="Pass">render.SetStencilPassOperation</page> the pixel. For more detailed information on the Stencil system, including usage examples, see the <page text="Stencils Render Reference">render_stencils</page> page </description> <realm>Client and Menu</realm> <args> <arg name="failOperation" type="number">Fail operation function, see <page>Enums/STENCILOPERATION</page>.</arg>⤶ <arg name="failOperation" type="Enums/STENCILOPERATION">⤶ The Stencil Operation to be performed if the Compare Function does not Pass a pixel.⤶ </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.⤶ ⤶ 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⤶ render.SetStencilWriteMask( 0xFF )⤶ render.SetStencilTestMask( 0xFF )⤶ render.SetStencilReferenceValue( 0 )⤶ render.SetStencilCompareFunction( STENCIL_ALWAYS )⤶ render.SetStencilPassOperation( 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 _, 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 )⤶ ⤶ -- Let everything render normally again⤶ render.SetStencilEnable( false )⤶ end )⤶ </code>⤶ <output><image src="basic_fail_operation.jpg" alt="800px"/></output>⤶ </example>⤶ <image src="b2b4c/8dc4ea6db700938.png" size="76553" name="FailOperationFlowChart.png" />