Instancing

Source/Instance.rs

@@ -0,0 +1,71 @@
+use bytemuck::{Pod, Zeroable};
+use std::mem;
+
+pub const NUM_INSTANCES_PER_ROW: u32 = 10;
+pub const NUM_INSTANCES: u32 = NUM_INSTANCES_PER_ROW * NUM_INSTANCES_PER_ROW;
+
+pub const INSTANCE_DISPLACEMENT: cgmath::Vector3<f32> = cgmath::Vector3::new(
+    NUM_INSTANCES_PER_ROW as f32 * 0.5,
+    0.0,
+    NUM_INSTANCES_PER_ROW as f32 * 0.5,
+);
+
+pub struct Instance {
+    pub position: cgmath::Vector3<f32>,
+    pub rotation: cgmath::Quaternion<f32>,
+}
+
+impl Instance {
+    pub fn to_raw(&self) -> InstanceRaw {
+        InstanceRaw {
+            model: (cgmath::Matrix4::from_translation(self.position)
+                * cgmath::Matrix4::from(self.rotation))
+            .into(),
+        }
+    }
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, Pod, Zeroable)]
+pub struct InstanceRaw {
+    pub model: [[f32; 4]; 4],
+}
+
+impl InstanceRaw {
+    pub fn desc<'a>() -> wgpu::VertexBufferLayout<'a> {
+        wgpu::VertexBufferLayout {
+            array_stride: mem::size_of::<InstanceRaw>() as wgpu::BufferAddress,
+            // We need to switch from using a step mode of Vertex to Instance
+            // This means that our shaders will only change to use the next
+            // instance when the shader starts processing a new instance
+            step_mode: wgpu::VertexStepMode::Instance,
+            attributes: &[
+                wgpu::VertexAttribute {
+                    offset: 0,
+                    // While our vertex shader only uses locations 0, and 1 now, in later tutorials we'll
+                    // be using 2, 3, and 4, for Vertex. We'll start at slot 5 not conflict with them later
+                    shader_location: 5,
+                    format: wgpu::VertexFormat::Float32x4,
+                },
+                // A mat4 takes up 4 vertex slots as it is technically 4 vec4s. We need to define a slot
+                // for each vec4. We'll have to reassemble the mat4 in
+                // the shader.
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 4]>() as wgpu::BufferAddress,
+                    shader_location: 6,
+                    format: wgpu::VertexFormat::Float32x4,
+                },
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 8]>() as wgpu::BufferAddress,
+                    shader_location: 7,
+                    format: wgpu::VertexFormat::Float32x4,
+                },
+                wgpu::VertexAttribute {
+                    offset: mem::size_of::<[f32; 12]>() as wgpu::BufferAddress,
+                    shader_location: 8,
+                    format: wgpu::VertexFormat::Float32x4,
+                },
+            ],
+        }
+    }
+}

Source/Main.rs

@@ -4,11 +4,16 @@
 mod _Camera;
 use _Camera::*;
 
+#[path = "Instance.rs"]
+mod _Instance;
+use _Instance::*;
+
 #[path = "Texture.rs"]
 mod _Texture;
 use _Texture::*;
 
 use bytemuck::{Pod, Zeroable};
+use cgmath::prelude::*;
 use image::GenericImageView;
 use std::mem;
 use wgpu::util::DeviceExt;
@@ -92,6 +97,8 @@ struct State {
     camera_buffer: wgpu::Buffer,
     camera_bind_group: wgpu::BindGroup,
     camera_controller: CameraController,
+    instances: Vec<Instance>,
+    instance_buffer: wgpu::Buffer,
 }
 
 impl State {
@@ -305,7 +312,7 @@ impl State {
             vertex: wgpu::VertexState {
                 module: &shader,
                 entry_point: "main",
-                buffers: &[Vertex::desc()],
+                buffers: &[Vertex::desc(), InstanceRaw::desc()],
             },
             fragment: Some(wgpu::FragmentState {
                 // 3.
@@ -354,6 +361,41 @@ impl State {
 
         let num_indices = INDICES.len() as u32;
 
+        // Instances
+
+        let instances = (0..NUM_INSTANCES_PER_ROW)
+            .flat_map(|z| {
+                (0..NUM_INSTANCES_PER_ROW).map(move |x| {
+                    let position = cgmath::Vector3 {
+                        x: x as f32,
+                        y: 0.0,
+                        z: z as f32,
+                    } - INSTANCE_DISPLACEMENT;
+
+                    let rotation = if position.is_zero() {
+                        // this is needed so an object at (0, 0, 0) won't get scaled to zero
+                        // as Quaternions can effect scale if they're not created correctly
+                        cgmath::Quaternion::from_axis_angle(
+                            cgmath::Vector3::unit_z(),
+                            cgmath::Deg(0.0),
+                        )
+                    } else {
+                        cgmath::Quaternion::from_axis_angle(position.normalize(), cgmath::Deg(45.0))
+                    };
+
+                    Instance { position, rotation }
+                })
+            })
+            .collect::<Vec<_>>();
+
+        let instance_data = instances.iter().map(Instance::to_raw).collect::<Vec<_>>();
+
+        let instance_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some("Instance Buffer"),
+            contents: bytemuck::cast_slice(&instance_data),
+            usage: wgpu::BufferUsages::VERTEX,
+        });
+
         Self {
             surface,
             device,
@@ -371,6 +413,8 @@ impl State {
             camera_buffer,
             camera_bind_group,
             camera_controller,
+            instances,
+            instance_buffer,
         }
     }
 
@@ -437,9 +481,10 @@ impl State {
             render_pass.set_bind_group(1, &self.camera_bind_group, &[]);
 
             render_pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
+            render_pass.set_vertex_buffer(1, self.instance_buffer.slice(..));
             render_pass.set_index_buffer(self.index_buffer.slice(..), wgpu::IndexFormat::Uint16);
 
-            render_pass.draw_indexed(0..self.num_indices, 0, 0..1);
+            render_pass.draw_indexed(0..self.num_indices, 0, 0..self.instances.len() as _);
         }
 
         // submit will accept anything that implements IntoIter