iridia-exec 0.5.0

//! What an evaluation asks of its caller, and the trait that answers it.
//!
//! A request names its resources by `R`: [`Element`] where the program's own interface is the vocabulary
//! ([`Backend`]), the D3D bind slot where [`crate::Sampler`] answers for a bytecode that counts slots.

use iridia::ResourceId;

/// A resource of the program's interface and, for an array of them (`binding_array`), the element the program's index
/// picked (0 for a resource that is not an array). An index past a bounded array's length is an error that stops the
/// evaluation (D3D12 leaves it undefined, so there is no answer to compare); the length of an unbounded array is the
/// caller's to check.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Element {
    /// The resource of the program's interface.
    pub id: ResourceId,
    /// The element of an array of resources the program's index picked; 0 for a resource that is not an array.
    pub index: u32,
}

/// A texture's shape as a request states it.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Dim {
    /// A one-dimensional texture.
    D1,
    /// A two-dimensional texture.
    D2,
    /// A three-dimensional texture.
    D3,
    /// A cube map.
    Cube,
}

/// How a request picks its level of detail. Gradients are three components wide: a 1D or 2D texture leaves the rest 0.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ImageLod {
    /// The implicit level, whose footprint a scalar evaluation leaves to the sampler.
    Implicit,
    /// The implicit level plus a bias the program states.
    Bias(f32),
    /// A level the program states.
    Level(f32),
    /// The coordinate's screen derivatives (d/dx, then d/dy): those the program states, or a quad's own for an
    /// implicit-level sample.
    Gradients([[f32; 3]; 2]),
    /// A quad's own derivatives plus the bias the program states.
    GradientsBias([[f32; 3]; 2], f32),
}

/// A sample of any texture: 1D, 2D, 3D, cube, arrayed, with an offset, a gather or a comparison.
#[derive(Clone, Copy, Debug)]
pub struct ImageSample<R> {
    /// The texture sampled: an interface [`Element`] or a bind slot, as `R` says.
    pub texture: R,
    /// The sampler, named the same way.
    pub sampler: R,
    /// The texture's shape.
    pub dim: Dim,
    /// The coordinate's components (1D: x; 2D: x, y; 3D and cube: x, y, z); the rest 0.
    pub coord: [f32; 3],
    /// An array's layer, as the program gives it (already rounded and clamped to 0 or more).
    pub layer: Option<f32>,
    /// How the level of detail is picked.
    pub lod: ImageLod,
    /// The constant texel offset (0 where the program states none).
    pub offset: [i32; 3],
    /// A gather: the component (0 to 3) whose four texels are returned.
    pub gather: Option<u8>,
    /// A comparison sample's reference value.
    pub depth_ref: Option<f32>,
    /// The texture is a depth texture: the first lane of the result is its (compared) depth.
    pub depth: bool,
}

/// A texel load (`ld`, `ld_ms`, a typed unordered-access load).
#[derive(Clone, Copy, Debug)]
pub struct ImageLoad<R> {
    /// The texture read.
    pub texture: R,
    /// The texture's shape.
    pub dim: Dim,
    /// A view of an unordered-access resource rather than a shader resource.
    pub storage: bool,
    /// The integer address of the texel (x, y, z; the rest 0).
    pub texel: [i32; 3],
    /// An array's layer.
    pub layer: Option<i32>,
    /// The sample of a multisampled texture.
    pub sample: Option<i32>,
    /// The mip level; `None` where the load states none.
    pub mip: Option<i32>,
}

/// Which property of a texture a query reads.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum QueryKind {
    /// The width, height and depth at `level` (as many as the dimension has).
    Size,
    /// The number of mip levels.
    Levels,
    /// The number of array layers.
    Layers,
    /// The number of samples per texel.
    Samples,
}

/// A `resinfo`-style query.
#[derive(Clone, Copy, Debug)]
pub struct ImageQuery<R> {
    /// The texture queried.
    pub texture: R,
    /// The texture's shape.
    pub dim: Dim,
    /// Which property is read.
    pub kind: QueryKind,
    /// The mip level a size is asked at; `None` where the query states none.
    pub level: Option<u32>,
}

/// A write to an unordered-access texture.
#[derive(Clone, Copy, Debug)]
pub struct ImageStore<R> {
    /// The unordered-access view written.
    pub view: R,
    /// Which view of an array of views (0 for a view that is not in an array).
    pub index: u32,
    /// The view's shape.
    pub dim: Dim,
    /// The integer address of the texel (x, y, z; the rest 0).
    pub texel: [u32; 3],
    /// An array's layer.
    pub layer: Option<u32>,
    /// The lanes as the program writes them (bits); only the first `lanes` are written.
    pub value: [u32; 4],
    /// How many of the value's lanes the program writes.
    pub lanes: u8,
}

/// What an atomic operation on a texel does with the word it holds and the program's value.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ImageAtomicOp {
    /// Add the program's value to the word.
    Add,
    /// Subtract the program's value from the word.
    Sub,
    /// Bitwise and.
    And,
    /// Bitwise or.
    Or,
    /// Bitwise exclusive or.
    Xor,
    /// The smaller of the two (signed or unsigned, as `ImageAtomic::signed` says).
    Min,
    /// The larger of the two (signed or unsigned, as `ImageAtomic::signed` says).
    Max,
    /// Store the program's value.
    Exchange,
}

/// An atomic operation on one texel of a single-channel 32-bit unordered-access texture. Its result is the word as it was
/// before; the program reads it when its `Statement::ImageAtomic` has a result.
#[derive(Clone, Copy, Debug)]
pub struct ImageAtomic<R> {
    /// The unordered-access view operated on.
    pub view: R,
    /// Which view of an array of views (0 for a view that is not in an array).
    pub index: u32,
    /// The view's shape.
    pub dim: Dim,
    /// The integer address of the texel (x, y, z; the rest 0).
    pub texel: [u32; 3],
    /// An array's layer.
    pub layer: Option<u32>,
    /// The operation.
    pub op: ImageAtomicOp,
    /// Whether `Min` and `Max` compare the words as signed integers.
    pub signed: bool,
    /// The program's operand.
    pub value: u32,
}

/// `TraceRay`: a ray shot into an acceleration structure. The payload is the words of the program's payload structure,
/// which the programs the ray runs read and write; the caller leaves it as the ray's last program did.
#[derive(Debug)]
pub struct TraceRay<'a> {
    /// The interface resource of the acceleration structure.
    pub scene: ResourceId,
    /// The ray's flags ([`crate::ray_flags`]).
    pub flags: u32,
    /// The instance inclusion mask: an instance is seen when it shares a bit with it.
    pub mask: u32,
    /// `RayContributionToHitGroupIndex`: added to the hit group index.
    pub hit_group_offset: u32,
    /// `MultiplierForGeometryContributionToHitGroupIndex`: the geometry index is multiplied by it.
    pub hit_group_stride: u32,
    /// `MissShaderIndex`: which miss program runs if nothing is hit.
    pub miss_index: u32,
    /// The ray's origin in world space.
    pub origin: [f32; 3],
    /// The nearest distance along the ray that counts as a hit.
    pub t_min: f32,
    /// The ray's direction in world space.
    pub direction: [f32; 3],
    /// The farthest distance along the ray that counts as a hit.
    pub t_max: f32,
    /// The words of the payload structure.
    pub payload: &'a mut [u32],
}

/// `ReportHit`: an intersection program reports a hit at `t` of kind `hit_kind`, with the words of its attributes.
#[derive(Debug)]
pub struct ReportHit<'a> {
    /// The distance along the ray of the hit.
    pub t: f32,
    /// The hit kind the intersection program reports.
    pub hit_kind: u32,
    /// The words of the hit attributes structure.
    pub attributes: &'a mut [u32],
}

/// `CallShader`: run the callable program `index` of the shader table on the words of a parameter structure.
#[derive(Debug)]
pub struct CallShader<'a> {
    /// Which callable program of the shader table.
    pub index: u32,
    /// The words of the parameter structure.
    pub parameter: &'a mut [u32],
}

/// Everything an evaluation asks of its caller: texture sampling, loads, queries, and the effects of unordered-access
/// writes. A request the caller cannot answer is an error that stops the evaluation. Reads of buffers need no call:
/// the buffers are bound before the run.
pub trait Backend {
    /// Answer a texture sample with the texel's four lanes, or an error that stops the evaluation.
    fn sample(&mut self, request: ImageSample<Element>) -> Result<[f32; 4], String>;
    /// The texel's four lanes as its view returns them: f32 bits for a float view, the integers otherwise.
    fn load(&mut self, request: ImageLoad<Element>) -> Result<[u32; 4], String> {
        Err(format!("resource {}: no loads given", request.texture.id.0))
    }
    /// Answer a size or level-count query with its lanes.
    fn query(&mut self, request: ImageQuery<Element>) -> Result<[u32; 4], String> {
        Err(format!("resource {}: no queries given", request.texture.id.0))
    }
    /// Write a texel of an unordered-access texture. The effect is the caller's: it reaches none of this evaluation's
    /// reads.
    fn store_image(&mut self, request: ImageStore<ResourceId>) -> Result<(), String> {
        Err(format!("resource {}: no stores given", request.view.0))
    }
    /// `TraceRay`, for a ray tracing pipeline's program: run what the ray hits and misses.
    fn trace_ray(&mut self, request: TraceRay<'_>) -> Result<(), String> {
        let _ = request;
        Err("no ray tracing pipeline given".into())
    }
    /// `ReportHit`, for an intersection program: whether the hit was accepted.
    fn report_hit(&mut self, request: ReportHit<'_>) -> Result<bool, String> {
        let _ = request;
        Err("no ray tracing pipeline given".into())
    }
    /// `CallShader`, for a ray tracing pipeline's program.
    fn call_shader(&mut self, request: CallShader<'_>) -> Result<(), String> {
        let _ = request;
        Err("no ray tracing pipeline given".into())
    }
    /// An atomic operation on one texel; its result the word as it was before.
    fn atomic_image(&mut self, request: ImageAtomic<ResourceId>) -> Result<u32, String> {
        Err(format!("resource {}: no image atomics given", request.view.0))
    }
    /// Words written to a buffer: the lanes `mask` marks of `value`, to the consecutive 32-bit words from word `word`
    /// of the buffer. The effect is the caller's: it reaches none of this evaluation's reads.
    fn store_buffer(&mut self, view: ResourceId, word: u32, value: [u32; 4], mask: u8) -> Result<(), String> {
        let _ = (word, value, mask);
        Err(format!("resource {}: no stores given", view.0))
    }
    /// `count` (1 to 4) consecutive 32-bit words from word `word` of a buffer the caller did not bind
    /// ([`super::Resources::buffers`]); lanes past `count` are 0.
    fn read_buffer(&mut self, view: ResourceId, word: u32, count: u8) -> Result<[u32; 4], String> {
        let _ = (word, count);
        Err(format!("resource {}: no buffer given", view.0))
    }
    /// How many words a buffer the caller did not bind has.
    fn buffer_words(&mut self, view: ResourceId) -> Result<u32, String> {
        Err(format!("resource {}: no buffer given", view.0))
    }
    /// An atomic add to word `word` of a buffer; its result the word as it was before.
    fn atomic_add(&mut self, view: ResourceId, word: u32, value: u32) -> Result<u32, String> {
        let _ = (word, value);
        Err(format!("resource {}: no atomics given", view.0))
    }
}