From 83295e01008bdf25e03f6b5aa18b93b735a5e326 Mon Sep 17 00:00:00 2001
From: Micha White <botahamec@outlook.com>
Date: Sun, 18 Sep 2022 16:45:05 -0400
Subject: instancing

---
 src/instance.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 src/instance.rs

(limited to 'src/instance.rs')

diff --git a/src/instance.rs b/src/instance.rs
new file mode 100644
index 0000000..6de0133
--- /dev/null
+++ b/src/instance.rs
@@ -0,0 +1,46 @@
+use std::mem::size_of;
+
+use bytemuck::{Pod, Zeroable};
+
+#[repr(C)]
+#[derive(Copy, Clone, Debug, PartialEq, Pod, Zeroable)]
+pub struct Instance {
+	/// Position on the screen
+	pub position: [f32; 2],
+	/// Relative size
+	pub size: [f32; 2],
+	/// Rotation, in radians
+	pub rotation: f32,
+	/// z-index
+	pub z_index: i32,
+}
+
+impl Default for Instance {
+	fn default() -> Self {
+		Self {
+			position: [0.0; 2],
+			size: [1.0; 2],
+			rotation: 0.0,
+			z_index: 0,
+		}
+	}
+}
+
+impl Instance {
+	// whenever this is updated, please also update `sprite.wgsl`
+	const ATTRIBUTES: [wgpu::VertexAttribute; 4] =
+		wgpu::vertex_attr_array![1 => Float32x2, 2 => Float32x2, 3 => Float32, 4 => Sint32];
+
+	pub(crate) fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
+		// make sure these two don't conflict
+		debug_assert_eq!(
+			Self::ATTRIBUTES[0].shader_location as usize,
+			crate::Vertex::ATTRIBUTES.len()
+		);
+		wgpu::VertexBufferLayout {
+			array_stride: size_of::<Self>() as wgpu::BufferAddress,
+			step_mode: wgpu::VertexStepMode::Instance,
+			attributes: &Self::ATTRIBUTES,
+		}
+	}
+}
-- 
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