[Merged by Bors] - Add multi draw indirect draw calls

crates/bevy_render/src/render_phase/draw_state.rs

@@ -283,6 +283,166 @@ impl<'a> TrackedRenderPass<'a> {
             .draw_indexed_indirect(indirect_buffer, indirect_offset);
     }
 
+    /// Dispatches multiple draw calls from the active vertex buffer(s) based on the contents of the `indirect_buffer`.
+    /// `count` draw calls are issued.
+    ///
+    /// The active vertex buffers can be set with [`TrackedRenderPass::set_vertex_buffer`].
+    ///
+    /// `indirect_buffer` should contain `count` tightly packed elements of the following structure:
+    ///
+    /// ```rust
+    /// #[repr(C)]
+    /// struct DrawIndirect {
+    ///     vertex_count: u32, // The number of vertices to draw.
+    ///     instance_count: u32, // The number of instances to draw.
+    ///     first_vertex: u32, // The Index of the first vertex to draw.
+    ///     first_instance: u32, // The instance ID of the first instance to draw.
+    ///     // has to be 0, unless [`Features::INDIRECT_FIRST_INSTANCE`] is enabled.
+    /// }
+    /// ```
+    pub fn multi_draw_indirect(
+        &mut self,
+        indirect_buffer: &'a Buffer,
+        indirect_offset: u64,
+        count: u32,
+    ) {
+        trace!(
+            "multi draw indirect: {:?} {}, {}x",
+            indirect_buffer,
+            indirect_offset,
+            count
+        );
+        self.pass
+            .multi_draw_indirect(indirect_buffer, indirect_offset, count);
+    }
+
+    /// Dispatches multiple draw calls from the active vertex buffer(s) based on the contents of the `indirect_buffer`.
+    /// The count buffer is read to determine how many draws to issue.
+    ///
+    /// The indirect buffer must be long enough to account for `max_count` draws, however only `count` elements
+    /// will be read, where `count` is the value read from `count_buffer` capped at `max_count`.
+    ///
+    /// The active vertex buffers can be set with [`TrackedRenderPass::set_vertex_buffer`].
+    ///
+    /// `indirect_buffer` should contain `count` tightly packed elements of the following structure:
+    ///
+    /// ```rust
+    /// #[repr(C)]
+    /// struct DrawIndirect {
+    ///     vertex_count: u32, // The number of vertices to draw.
+    ///     instance_count: u32, // The number of instances to draw.
+    ///     first_vertex: u32, // The Index of the first vertex to draw.
+    ///     first_instance: u32, // The instance ID of the first instance to draw.
+    ///     // has to be 0, unless [`Features::INDIRECT_FIRST_INSTANCE`] is enabled.
+    /// }
+    /// ```
+    pub fn multi_draw_indirect_count(
+        &mut self,
+        indirect_buffer: &'a Buffer,
+        indirect_offset: u64,
+        count_buffer: &'a Buffer,
+        count_offset: u64,
+        max_count: u32,
+    ) {
+        trace!(
+            "multi draw indirect count: {:?} {}, ({:?} {})x, max {}x",
+            indirect_buffer,
+            indirect_offset,
+            count_buffer,
+            count_offset,
+            max_count
+        );
+        self.pass.multi_draw_indirect_count(
+            indirect_buffer,
+            indirect_offset,
+            count_buffer,
+            count_offset,
+            max_count,
+        );
+    }
+
+    /// Dispatches multiple draw calls from the active index buffer and the active vertex buffers,
+    /// based on the contents of the `indirect_buffer`. `count` draw calls are issued.
+    ///
+    /// The active index buffer can be set with [`TrackedRenderPass::set_index_buffer`], while the active
+    /// vertex buffers can be set with [`TrackedRenderPass::set_vertex_buffer`].
+    ///
+    /// `indirect_buffer` should contain `count` tightly packed elements of the following structure:
+    ///
+    /// ```rust
+    /// #[repr(C)]
+    /// struct DrawIndexedIndirect {
+    ///     vertex_count: u32, // The number of vertices to draw.
+    ///     instance_count: u32, // The number of instances to draw.
+    ///     first_index: u32, // The base index within the index buffer.
+    ///     vertex_offset: i32, // The value added to the vertex index before indexing into the vertex buffer.
+    ///     first_instance: u32, // The instance ID of the first instance to draw.
+    ///     // has to be 0, unless [`Features::INDIRECT_FIRST_INSTANCE`] is enabled.
+    /// }
+    /// ```
+    pub fn multi_draw_indexed_indirect(
+        &mut self,
+        indirect_buffer: &'a Buffer,
+        indirect_offset: u64,
+        count: u32,
+    ) {
+        trace!(
+            "multi draw indexed indirect: {:?} {}, {}x",
+            indirect_buffer,
+            indirect_offset,
+            count
+        );
+        self.pass
+            .multi_draw_indexed_indirect(indirect_buffer, indirect_offset, count);
+    }
+
+    /// Dispatches multiple draw calls from the active index buffer and the active vertex buffers,
+    /// based on the contents of the `indirect_buffer`. The count buffer is read to determine how many draws to issue.
+    ///
+    /// The indirect buffer must be long enough to account for `max_count` draws, however only `count` elements
+    /// will be read, where `count` is the value read from `count_buffer` capped at `max_count`.
+    ///
+    /// The active index buffer can be set with [`TrackedRenderPass::set_index_buffer`], while the active
+    /// vertex buffers can be set with [`TrackedRenderPass::set_vertex_buffer`].
+    ///
+    /// `indirect_buffer` should contain `count` tightly packed elements of the following structure:
+    ///
+    /// ```rust
+    /// #[repr(C)]
+    /// struct DrawIndexedIndirect {
+    ///     vertex_count: u32, // The number of vertices to draw.
+    ///     instance_count: u32, // The number of instances to draw.
+    ///     first_index: u32, // The base index within the index buffer.
+    ///     vertex_offset: i32, // The value added to the vertex index before indexing into the vertex buffer.
+    ///     first_instance: u32, // The instance ID of the first instance to draw.
+    ///     // has to be 0, unless [`Features::INDIRECT_FIRST_INSTANCE`] is enabled.
+    /// }
+    /// ```
+    pub fn multi_draw_indexed_indirect_count(
+        &mut self,
+        indirect_buffer: &'a Buffer,
+        indirect_offset: u64,
+        count_buffer: &'a Buffer,
+        count_offset: u64,
+        max_count: u32,
+    ) {
+        trace!(
+            "multi draw indexed indirect count: {:?} {}, ({:?} {})x, max {}x",
+            indirect_buffer,
+            indirect_offset,
+            count_buffer,
+            count_offset,
+            max_count
+        );
+        self.pass.multi_draw_indexed_indirect_count(
+            indirect_buffer,
+            indirect_offset,
+            count_buffer,
+            count_offset,
+            max_count,
+        );
+    }
+
     /// Sets the stencil reference.
     ///
     /// Subsequent stencil tests will test against this value.