Make the cube rotate

src/app/dem_renderer.rs

@@ -12,6 +12,8 @@ pub struct DemRenderer {
     vertex_buffer: wgpu::Buffer,
     index_buffer: wgpu::Buffer,
     index_count: usize,
+    uniforms: Uniforms,
+    animation_start: std::time::Instant,
 }
 
 #[repr(C)]
@@ -20,6 +22,51 @@ struct Vertex {
     position: [f32; 4],
 }
 
+struct Uniforms {
+    projection_matrix: glam::Mat4,
+    view_matrix: glam::Mat4,
+    buffer: wgpu::Buffer,
+}
+
+impl Uniforms {
+    fn new(device: &wgpu::Device, aspect_ratio: f32) -> Self {
+        let projection_matrix =
+            glam::Mat4::perspective_rh(std::f32::consts::FRAC_PI_4, aspect_ratio, 1.0, 10.0);
+        let view_matrix = glam::Mat4::look_at_rh(glam::Vec3::ZERO, glam::Vec3::ZERO, glam::Vec3::Z);
+        let camera_matrix = projection_matrix * view_matrix;
+        let camera_matrix_ref: &[f32; 16] = camera_matrix.as_ref();
+        let buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some("Uniform Buffer"),
+            contents: bytemuck::cast_slice(camera_matrix_ref),
+            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+        });
+        Self {
+            projection_matrix,
+            view_matrix,
+            buffer,
+        }
+    }
+
+    fn set_camera_position(&mut self, position: glam::Vec3) {
+        self.view_matrix = glam::Mat4::look_at_rh(position, glam::Vec3::ZERO, glam::Vec3::Z);
+    }
+
+    fn set_aspect_ratio(&mut self, ratio: f32) {
+        self.projection_matrix =
+            glam::Mat4::perspective_rh(std::f32::consts::FRAC_PI_4, ratio, 1.0, 10.0);
+    }
+
+    fn update_buffer(&self, queue: &wgpu::Queue) {
+        let camera_matrix = self.projection_matrix * self.view_matrix;
+        let camera_matrix_ref: &[f32; 16] = camera_matrix.as_ref();
+        queue.write_buffer(&self.buffer, 0, bytemuck::cast_slice(camera_matrix_ref))
+    }
+
+    fn binding(&self) -> wgpu::BindingResource<'_> {
+        self.buffer.as_entire_binding()
+    }
+}
+
 impl DemRenderer {
     pub fn new(
         source: Rc<Dem>,
@@ -42,16 +89,10 @@ impl DemRenderer {
 
         let index_count = index_data.len();
 
-        let uniform_buf = {
-            let mx_total =
-                generate_matrix(surface_config.width as f32 / surface_config.height as f32);
-            let mx_ref: &[f32; 16] = mx_total.as_ref();
-            device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
-                label: Some("Uniform Buffer"),
-                contents: bytemuck::cast_slice(mx_ref),
-                usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
-            })
-        };
+        let uniforms = Uniforms::new(
+            device,
+            surface_config.width as f32 / surface_config.height as f32,
+        );
 
         let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: None,
@@ -83,7 +124,7 @@ impl DemRenderer {
             layout: &bind_group_layout,
             entries: &[wgpu::BindGroupEntry {
                 binding: 0,
-                resource: uniform_buf.as_entire_binding(),
+                resource: uniforms.binding(),
             }],
             label: Some("DemRendererBindGroup"),
         });
@@ -140,6 +181,8 @@ impl DemRenderer {
             vertex_buffer,
             index_buffer,
             index_count,
+            animation_start: std::time::Instant::now(),
+            uniforms,
         }
     }
 
@@ -147,6 +190,9 @@ impl DemRenderer {
         let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
             label: Some("DemRendererCommandEncoder"),
         });
+        self.uniforms
+            .set_camera_position(get_animated_camera_position(self.animation_start.elapsed()));
+        self.uniforms.update_buffer(queue);
         {
             let mut rpass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                 label: Some("DemRendererRenderPass"),
@@ -224,13 +270,11 @@ fn create_vertices() -> (Vec<Vertex>, Vec<u16>) {
     (vertex_data.to_vec(), index_data.to_vec())
 }
 
-fn generate_matrix(aspect_ratio: f32) -> glam::Mat4 {
-    let projection =
-        glam::Mat4::perspective_rh(std::f32::consts::FRAC_PI_4, aspect_ratio, 1.0, 10.0);
-    let view = glam::Mat4::look_at_rh(
-        glam::Vec3::new(1.5f32, -5.0, 3.0),
-        glam::Vec3::ZERO,
-        glam::Vec3::Z,
-    );
-    projection * view
+fn get_animated_camera_position(animation_time: std::time::Duration) -> glam::Vec3 {
+    let animation_phase = 2.0 * std::f32::consts::PI * (animation_time.as_secs_f32() % 10.0) / 10.0;
+    glam::Vec3::new(
+        5.0 * f32::sin(animation_phase),
+        5.0 * f32::cos(animation_phase),
+        3.0,
+    )
 }