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Encoder API example
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trait Renderer<'a> { | |
/// Takes a pipeline, an ordered list of field descriptors and returns pointers into mapped GPU buffers for each field. | |
fn pipeline_outputs( | |
&mut self, | |
pipeline: Handle<Pipeline>, | |
fields: &[FieldDesc], | |
entity_offset: u32, | |
) -> &'a [EncodeTarget]; | |
} | |
/// Enum of supported field types | |
enum FieldType { | |
Matrix4x4, | |
// etc.. | |
} | |
/// Name and type of a field that can be linked to a GPU buffer struct | |
struct FieldDesc { | |
name: &'static str, | |
typ: FieldType, | |
} | |
/// Wrapper around a pointer that can be written to. Unsafe | |
struct EncodeTarget { | |
dst: Option<*mut u8>, | |
} | |
impl EncodeTarget { | |
#[inline] | |
unsafe fn write<T: Copy>(&self, value: &T) { | |
if self.dst.is_none() { return } | |
let ptr = self.dst.unwrap() as *mut T; | |
*ptr = *value; | |
} | |
} | |
/// Encoder is responsible for encoding `World` component data into GPU buffers. | |
trait Encoder<'a, T: SystemData> { | |
/// `pipelines` can use the `Renderer` to build pipelines dynamically or use a cached pipeline | |
fn pipelines(data: &T, renderer: &Renderer) -> Vec<Handle<Pipeline>>; | |
/// `fields` returns an ordered list of field descriptors that are used by the `Renderer` to find GPU buffer pointers | |
fn fields() -> &'a [FieldDesc]; | |
/// `encode` writes data from components to the target GPU buffer pointers. | |
/// `outputs` is required to have the same order and size as the return value of `fields`. | |
fn encode(data: &T, outputs: &[EncodeTarget]); | |
} | |
// The Encoder implementation is quite verbose and I think we can use macros to derive most of it based on the component types. | |
static ASDF_FIELDS: &'static [FieldDesc] = &[FieldDesc { | |
name: "iso", | |
typ: FieldType::Matrix4x4, | |
}]; | |
impl<'a> Encoder<'a, Self> for (Transform, Renderable) { | |
#[inline] | |
fn pipelines((_, renderable): &Self, _: &Renderer) -> Vec<Handle<Pipeline>> { | |
vec![renderable.pipeline] | |
} | |
#[inline] | |
fn fields() -> &'a [FieldDesc] { | |
ASDF_FIELDS | |
} | |
#[inline] | |
fn encode((transform, _): &Self, outputs: &[EncodeTarget]) { | |
unsafe { | |
outputs[0].write(&transform.iso); | |
} | |
} | |
} | |
#[inline] | |
fn run_encoder<'a, S: SystemData, T: Encoder<'a, S>>( | |
data: &S, | |
renderer: &mut Renderer, | |
entity_offset: u32, | |
) { | |
let pipelines = T::pipelines(data, renderer); | |
for pipeline in pipelines { | |
let fields = T::fields(); | |
let outputs = renderer.pipeline_outputs(pipeline, fields, entity_offset); | |
T::encode(data, outputs); | |
} | |
} |
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