Add depth testing

src/main.zig

@@ -60,6 +60,8 @@ random: std.rand.Random,
 app_timer: core.Timer,
 title_timer: core.Timer,
 
+depth_texture: *gpu.Texture,
+depth_texture_view: *gpu.TextureView,
 pipeline: *gpu.RenderPipeline,
 scene_uniform_buffer: *gpu.Buffer,
 scene_uniform_bind_group: *gpu.BindGroup,
@@ -87,6 +89,16 @@ pub fn init(app: *App) !void {
     app.app_timer = try core.Timer.start();
     app.title_timer = try core.Timer.start();
 
+    // Create a depth texture. This is used to ensure that when things are
+    // rendered, an object behind another won't draw over one in front, simply
+    // because it was rendered at a later point in time.
+    app.depth_texture = core.device.createTexture(&.{
+        .usage = .{ .render_attachment = true },
+        .size = .{ .width = core.descriptor.width, .height = core.descriptor.height },
+        .format = .depth24_plus,
+    });
+    app.depth_texture_view = app.depth_texture.createView(null);
+
     const shader_module = core.device.createShaderModuleWGSL("shader.wgsl", @embedFile("shader.wgsl"));
     defer shader_module.release();
 
@@ -105,16 +117,21 @@ pub fn init(app: *App) !void {
                 }),
             },
         }),
-        .fragment = &gpu.FragmentState.init(.{
-            .module = shader_module,
-            .entry_point = "frag_main",
-            .targets = &.{.{ .format = core.descriptor.format }},
-        }),
         .primitive = .{
             .topology = .triangle_list,
             .front_face = .ccw,
             .cull_mode = .back,
         },
+        .depth_stencil = &.{
+            .format = .depth24_plus,
+            .depth_write_enabled = .true,
+            .depth_compare = .less,
+        },
+        .fragment = &gpu.FragmentState.init(.{
+            .module = shader_module,
+            .entry_point = "frag_main",
+            .targets = &.{.{ .format = core.descriptor.format }},
+        }),
     });
 
     // Set up scene related uniform buffers and bind groups.
@@ -283,6 +300,8 @@ pub fn deinit(app: *App) void {
     // in the order they were created in `init`.
     defer core.deinit();
     defer _ = app.gpa.deinit(); // TODO: Check for memory leaks?
+    defer app.depth_texture.release();
+    defer app.depth_texture_view.release();
     defer app.pipeline.release();
     defer app.scene_uniform_buffer.release();
     defer app.scene_uniform_bind_group.release();
@@ -340,6 +359,12 @@ pub fn update(app: *App) !bool {
             .load_op = .clear,
             .store_op = .store,
         }},
+        .depth_stencil_attachment = &.{
+            .view = app.depth_texture_view,
+            .depth_load_op = .clear,
+            .depth_store_op = .store,
+            .depth_clear_value = 1.0,
+        },
     });
 
     // Create a `WGPUCommandEncoder` which provides an interface for recording GPU commands.