Trait bevy_render::render_phase::RenderCommand
source · pub trait RenderCommand<P: PhaseItem> {
type Param: SystemParam + 'static;
type ViewQuery: ReadOnlyQueryData;
type ItemQuery: ReadOnlyQueryData;
// Required method
fn render<'w>(
item: &P,
view: ROQueryItem<'w, Self::ViewQuery>,
entity: Option<ROQueryItem<'w, Self::ItemQuery>>,
param: SystemParamItem<'w, '_, Self::Param>,
pass: &mut TrackedRenderPass<'w>
) -> RenderCommandResult;
}Expand description
RenderCommands are modular standardized pieces of render logic that can be composed into
Draw functions.
To turn a stateless render command into a usable draw function it has to be wrapped by a
RenderCommandState.
This is done automatically when registering a render command as a Draw function via the
AddRenderCommand::add_render_command method.
Compared to the draw function the required ECS data is fetched automatically
(by the RenderCommandState) from the render world.
Therefore the three types Param,
ViewQuery and
ItemQuery are used.
They specify which information is required to execute the render command.
Multiple render commands can be combined together by wrapping them in a tuple.
§Example
The DrawMaterial draw function is created from the following render command
tuple. Const generics are used to set specific bind group locations:
pub type DrawMaterial<M> = (
SetItemPipeline,
SetMeshViewBindGroup<0>,
SetMeshBindGroup<1>,
SetMaterialBindGroup<M, 2>,
DrawMesh,
);Required Associated Types§
sourcetype Param: SystemParam + 'static
type Param: SystemParam + 'static
Specifies the general ECS data (e.g. resources) required by RenderCommand::render.
When fetching resources, note that, due to lifetime limitations of the Deref trait,
SRes::into_inner must be called on each SRes reference in the
RenderCommand::render method, instead of being automatically dereferenced as is the
case in normal systems.
All parameters have to be read only.
sourcetype ViewQuery: ReadOnlyQueryData
type ViewQuery: ReadOnlyQueryData
Specifies the ECS data of the view entity required by RenderCommand::render.
The view entity refers to the camera, or shadow-casting light, etc. from which the phase item will be rendered from. All components have to be accessed read only.
sourcetype ItemQuery: ReadOnlyQueryData
type ItemQuery: ReadOnlyQueryData
Specifies the ECS data of the item entity required by RenderCommand::render.
The item is the entity that will be rendered for the corresponding view. All components have to be accessed read only.
For efficiency reasons, Bevy doesn’t always extract entities to the
render world; for instance, entities that simply consist of meshes are
often not extracted. If the entity doesn’t exist in the render world,
the supplied query data will be None.
Required Methods§
sourcefn render<'w>(
item: &P,
view: ROQueryItem<'w, Self::ViewQuery>,
entity: Option<ROQueryItem<'w, Self::ItemQuery>>,
param: SystemParamItem<'w, '_, Self::Param>,
pass: &mut TrackedRenderPass<'w>
) -> RenderCommandResult
fn render<'w>( item: &P, view: ROQueryItem<'w, Self::ViewQuery>, entity: Option<ROQueryItem<'w, Self::ItemQuery>>, param: SystemParamItem<'w, '_, Self::Param>, pass: &mut TrackedRenderPass<'w> ) -> RenderCommandResult
Renders a PhaseItem by recording commands (e.g. setting pipelines, binding bind groups,
issuing draw calls, etc.) via the TrackedRenderPass.
Object Safety§
This trait is not object safe.