      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239

    // Copyright (c) 2016 The vulkano developers
    // Licensed under the Apache License, Version 2.0
    // <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT
    // license <LICENSE-MIT or http://opensource.org/licenses/MIT>,
    // at your option. All files in the project carrying such
    // notice may not be copied, modified, or distributed except
    // according to those terms.

    //! Depth and stencil operations description.
    //!
    //! After the fragment shader has finished running, each fragment goes through the depth
    //! and stencil tests.
    //!
    //! The depth test passes of fails depending on how the depth value of each fragment compares
    //! to the existing depth value in the depth buffer at that fragment's location. Depth values
    //! are always between 0.0 and 1.0.
    //!
    //! The stencil test passes or fails depending on how a reference value compares to the existing
    //! value in the stencil buffer at each fragment's location. Depending on the outcome of the
    //! depth and stencil tests, the value of the stencil buffer at that location can be updated.

    use std::ops::Range;
    use std::u32;
    use vk;

    /// Configuration of the depth and stencil tests.
    #[derive(Debug, Clone)]
    pub struct DepthStencil {
        /// Comparison to use between the depth value of each fragment and the depth value currently
        /// in the depth buffer.
        pub depth_compare: Compare,

        /// If `true`, then the value in the depth buffer will be updated when the depth test succeeds.
        pub depth_write: bool,

        /// Allows you to ask the GPU to exclude fragments that are outside of a certain range. This is
        /// done in addition to the regular depth test.
        pub depth_bounds_test: DepthBounds,

        /// Stencil operations to use for points, lines and triangles whose front is facing the user.
        pub stencil_front: Stencil,

        /// Stencil operations to use for triangles whose back is facing the user.
        pub stencil_back: Stencil,
    }

    impl DepthStencil {
        /// Creates a `DepthStencil` where both the depth and stencil tests are disabled and have
        /// no effect.
        #[inline]
        pub fn disabled() -> DepthStencil {
            DepthStencil {
                depth_write: false,
                depth_compare: Compare::Always,
                depth_bounds_test: DepthBounds::Disabled,
                stencil_front: Default::default(),
                stencil_back: Default::default(),
            }
        }

        /// Creates a `DepthStencil` with a `Less` depth test, `depth_write` set to true, and stencil
        /// testing disabled.
        #[inline]
        pub fn simple_depth_test() -> DepthStencil {
            DepthStencil {
                depth_write: true,
                depth_compare: Compare::Less,
                depth_bounds_test: DepthBounds::Disabled,
                stencil_front: Default::default(),
                stencil_back: Default::default(),
            }
        }
    }

    impl Default for DepthStencil {
        #[inline]
        fn default() -> DepthStencil {
            DepthStencil::disabled()
        }
    }

    /// Configuration of a stencil test.
    #[derive(Debug, Copy, Clone)]
    pub struct Stencil {
        /// The comparison to perform between the existing stencil value in the stencil buffer, and
        /// the reference value (given by `reference`).
        pub compare: Compare,

        /// The operation to perform when both the depth test and the stencil test passed.
        pub pass_op: StencilOp,

        /// The operation to perform when the stencil test failed.
        pub fail_op: StencilOp,

        /// The operation to perform when the stencil test passed but the depth test failed.
        pub depth_fail_op: StencilOp,

        /// Selects the bits of the unsigned integer stencil values participating in the stencil test.
        ///
        /// Ignored if `compare` is `Never` or `Always`.
        ///
        /// If `None`, then this value is dynamic and will need to be set when drawing. Doesn't apply
        /// if `compare` is `Never` or `Always`.
        ///
        /// Note that if this value is `Some` in `stencil_front`, it must also be `Some` in
        /// `stencil_back` (but the content can be different). If this value is `None` in
        /// `stencil_front`, then it must also be `None` in `stencil_back`. This rule doesn't apply
        /// if `compare` is `Never` or `Always`.
        pub compare_mask: Option<u32>,

        /// Selects the bits of the unsigned integer stencil values updated by the stencil test in the
        /// stencil framebuffer attachment.
        ///
        /// If `None`, then this value is dynamic and will need to be set when drawing.
        ///
        /// Note that if this value is `Some` in `stencil_front`, it must also be `Some` in
        /// `stencil_back` (but the content can be different). If this value is `None` in
        /// `stencil_front`, then it must also be `None` in `stencil_back`.
        pub write_mask: Option<u32>,

        /// Reference value that is used in the unsigned stencil comparison.
        ///
        /// If `None`, then this value is dynamic and will need to be set when drawing.
        ///
        /// Note that if this value is `Some` in `stencil_front`, it must also be `Some` in
        /// `stencil_back` (but the content can be different). If this value is `None` in
        /// `stencil_front`, then it must also be `None` in `stencil_back`.
        pub reference: Option<u32>,
    }

    impl Stencil {
        /// Returns true if the stencil operation will always result in `Keep`.
        #[inline]
        pub fn always_keep(&self) -> bool {
            match self.compare {
                Compare::Always => self.pass_op == StencilOp::Keep &&
                    self.depth_fail_op == StencilOp::Keep,
                Compare::Never => self.fail_op == StencilOp::Keep,
                _ => self.pass_op == StencilOp::Keep && self.fail_op == StencilOp::Keep &&
                    self.depth_fail_op == StencilOp::Keep,
            }
        }
    }

    impl Default for Stencil {
        #[inline]
        fn default() -> Stencil {
            Stencil {
                compare: Compare::Never,
                pass_op: StencilOp::Keep,
                fail_op: StencilOp::Keep,
                depth_fail_op: StencilOp::Keep,
                compare_mask: Some(u32::MAX),
                write_mask: Some(u32::MAX),
                reference: Some(u32::MAX),
            }
        }
    }

    /// Operation to perform after the depth and stencil tests.
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    #[repr(u32)]
    pub enum StencilOp {
        Keep = vk::STENCIL_OP_KEEP,
        Zero = vk::STENCIL_OP_ZERO,
        Replace = vk::STENCIL_OP_REPLACE,
        IncrementAndClamp = vk::STENCIL_OP_INCREMENT_AND_CLAMP,
        DecrementAndClamp = vk::STENCIL_OP_DECREMENT_AND_CLAMP,
        Invert = vk::STENCIL_OP_INVERT,
        IncrementAndWrap = vk::STENCIL_OP_INCREMENT_AND_WRAP,
        DecrementAndWrap = vk::STENCIL_OP_DECREMENT_AND_WRAP,
    }

    /// Enum to specify which stencil state to use
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    #[repr(u32)]
    pub enum StencilFaceFlags {
        StencilFaceFrontBit = vk::STENCIL_FACE_FRONT_BIT,
        StencilFaceBackBit = vk::STENCIL_FACE_BACK_BIT,
        StencilFrontAndBack = vk::STENCIL_FRONT_AND_BACK,
    }

    /// Container for dynamic state FaceFlags and value
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    pub struct DynamicStencilValue {
        pub face: StencilFaceFlags,
        pub value: u32,
    }

    /// Allows you to ask the GPU to exclude fragments that are outside of a certain range.
    #[derive(Debug, Clone, PartialEq)]
    pub enum DepthBounds {
        /// The test is disabled. All fragments pass the depth bounds test.
        Disabled,

        /// Fragments that are within the given range do pass the test. Values are depth values
        /// between 0.0 and 1.0.
        Fixed(Range<f32>),

        /// The depth bounds test is enabled, but the range will need to specified when you submit
        /// a draw command.
        Dynamic,
    }

    impl DepthBounds {
        /// Returns true if equal to `DepthBounds::Dynamic`.
        #[inline]
        pub fn is_dynamic(&self) -> bool {
            match self {
                &DepthBounds::Dynamic => true,
                _ => false,
            }
        }
    }

    /// Specifies how two values should be compared to decide whether a test passes or fails.
    ///
    /// Used for both depth testing and stencil testing.
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    #[repr(u32)]
    pub enum Compare {
        /// The test never passes.
        Never = vk::COMPARE_OP_NEVER,
        /// The test passes if `value < reference_value`.
        Less = vk::COMPARE_OP_LESS,
        /// The test passes if `value == reference_value`.
        Equal = vk::COMPARE_OP_EQUAL,
        /// The test passes if `value <= reference_value`.
        LessOrEqual = vk::COMPARE_OP_LESS_OR_EQUAL,
        /// The test passes if `value > reference_value`.
        Greater = vk::COMPARE_OP_GREATER,
        /// The test passes if `value != reference_value`.
        NotEqual = vk::COMPARE_OP_NOT_EQUAL,
        /// The test passes if `value >= reference_value`.
        GreaterOrEqual = vk::COMPARE_OP_GREATER_OR_EQUAL,
        /// The test always passes.
        Always = vk::COMPARE_OP_ALWAYS,
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)