Going crazy with translations

src/gl_helper/model.zig

@@ -7,38 +7,144 @@ const Mesh = @import("mesh.zig");
 const Shader = @import("shader.zig");
 const Tree = @import("../tree.zig").Tree;
 
+pub const Animation = struct {
+    rotation: zm.Quat,
+    translation: zm.Mat,
+};
+
 pub const JointData = struct {
     mesh: Mesh,
-    translation: zm.Mat,
-    rotation: zm.Quat,
+    animated_transform: zm.Mat = zm.identity(),
+    local_bind_transform: zm.Mat,
+    inverse_bind_transform: zm.Mat = zm.identity(),
+    keyframes: [2]Animation,
+    count: usize,
+
+    var counter: usize = 0;
+
+    pub fn init(mesh: Mesh, translation: zm.Mat, rotation: zm.Quat, keyframes: [2]zm.Quat) JointData {
+        const res = JointData{
+            .mesh = mesh,
+            .local_bind_transform = zm.mul(
+                zm.quatToMat(rotation),
+                translation,
+            ),
+            .count = counter,
+            .keyframes = .{
+                .{ .rotation = keyframes[0], .translation = translation },
+                .{ .rotation = keyframes[1], .translation = translation },
+            },
+        };
+        counter += 1;
+        return res;
+    }
 };
 
 data: Tree(JointData),
+animaton_duration: f32 = 1,
+animaton_time: f32 = 0,
 
-pub fn init(
-    data: Tree(JointData),
-) @This() {
+pub fn init(data: Tree(JointData)) !@This() {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const arena_allocator = arena.allocator();
+
+    var c_data = data;
+
+    var iter = try c_data.levelOrderIterator(arena_allocator);
+
+    while (iter.next()) |node| {
+        for (node.children.items) |*child| {
+            child.val.local_bind_transform = zm.mul(
+                child.val.local_bind_transform,
+                node.val.local_bind_transform,
+            );
+        }
+    }
     return .{ .data = data };
 }
 
-pub fn draw(self: *@This(), shader: Shader) void {
-    var iter = self.data.depthFirstIterator();
-    while (iter.next()) |node| {
-        var rotation = node.val.rotation;
-        var current = node;
-        while (current.parent) |parent| {
-            rotation = zm.qmul(rotation, parent.val.rotation);
-            current = parent;
-        }
+pub fn draw(self: *@This(), shader: Shader) !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const allocator = arena.allocator();
 
-        const model_matrix = zm.mul(zm.quatToMat(rotation), node.val.translation);
-        const normal_matrix = zm.transpose(zm.inverse(model_matrix));
+    var iter = try self.data.preOrderIterator(allocator);
+    defer iter.deinit(allocator);
+
+    while (iter.next()) |node| {
+        const model_matrix = zm.mul(
+            node.val.animated_transform,
+            node.val.local_bind_transform,
+        );
         shader.updateUniformMatrix("u_model_matrix", &.{model_matrix});
-        shader.updateUniformMatrix("u_normal_matrix", &.{normal_matrix});
+        shader.updateUniformMatrix("u_normal_matrix", &.{zm.transpose(zm.inverse(model_matrix))});
         node.val.mesh.draw(shader);
     }
 }
 
-pub fn deinit(self: *@This(), allocator: std.mem.Allocator) void {
-    self.data.deinit(allocator);
+pub fn animate(self: *@This(), delta_time: f32) !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const arena_allocator = arena.allocator();
+
+    var iter = try self.data.levelOrderIterator(arena_allocator);
+
+    self.animaton_time += delta_time;
+
+    if (self.animaton_time / self.animaton_duration < 1) {
+        while (iter.next()) |node| {
+            node.val.animated_transform = zm.mul(
+                zm.quatToMat(zm.slerp(
+                    node.val.keyframes[0].rotation,
+                    node.val.keyframes[1].rotation,
+                    self.animaton_time / self.animaton_duration,
+                )),
+                node.val.keyframes[0].translation,
+            );
+
+            for (node.children.items) |*child| {
+                child.val.animated_transform = zm.mul(
+                    node.val.animated_transform,
+                    child.val.animated_transform,
+                );
+            }
+        }
+    } else if (self.animaton_time / self.animaton_duration < 2) {
+        while (iter.next()) |node| {
+            node.val.animated_transform = zm.mul(
+                zm.quatToMat(zm.slerp(
+                    node.val.keyframes[1].rotation,
+                    node.val.keyframes[0].rotation,
+                    self.animaton_time / self.animaton_duration - 1,
+                )),
+                node.val.keyframes[1].translation,
+            );
+
+            for (node.children.items) |*child| {
+                child.val.animated_transform = zm.mul(
+                    child.val.animated_transform,
+                    node.val.animated_transform,
+                );
+            }
+        }
+    } else {
+        self.animaton_time = 0;
+        return;
+    }
+
+    iter = try self.data.levelOrderIterator(arena_allocator);
+
+    // while (iter.next()) |node| {
+    //     for (node.children.items) |*child| {
+    //         child.val.animated_transform = zm.mul(
+    //             node.val.animated_transform,
+    //             child.val.animated_transform,
+    //         );
+    //     }
+    // }
+}
+
+pub fn deinit(self: *@This(), allocator: std.mem.Allocator) !void {
+    try self.data.deinit(allocator);
 }

src/main.zig

@@ -96,37 +96,8 @@ pub fn main() !void {
     const floor = initFloor(floor_texture);
     defer floor.delete();
 
-    var shape = Shape.initCube();
-    defer shape.deinit();
-
-    shape.unweld();
-    shape.computeNormals();
-    shape.translate(-0.5, -1, -0.5);
-
-    var chest = shape.clone();
-    defer chest.deinit();
-    chest.scale(0.3, 0.4, 0.15);
-
-    var model_data = Tree(Model.JointData).init(.{
-        .mesh = Mesh.initShape(chest, robot_texture, .triangles),
-        .translation = zm.translation(0, 0.425 + 0.4, 0),
-        .rotation = zm.qidentity(),
-    });
-
-    var head = shape.clone();
-    defer head.deinit();
-    head.scale(0.1, 0.1, 0.1);
-
-    try model_data.root.append(allocator, .{
-        .mesh = Mesh.initShape(head, robot_texture, .triangles),
-        .translation = zm.translation(0, 0.425 + 0.4 + 0.1, 0),
-        .rotation = zm.qidentity(),
-    });
-
-    var robot = Model.init(model_data);
-
-    // var robot = try initRobot(allocator, robot_texture);
-    defer robot.deinit(allocator);
+    var robot = try initRobot(allocator, robot_texture);
+    defer robot.deinit(allocator) catch {};
 
     // uniform data
     var light_color = zm.f32x4(1, 1, 1, 1);
@@ -162,7 +133,6 @@ pub fn main() !void {
     var previous_time = glfw_helper.getTime();
     var current_time: f64 = 0;
     var delta_time: f64 = undefined;
-    // var frame_counter: u16 = 0;
 
     // OpenGL setup
     const clear_color = FloatColor.sky_blue;
@@ -191,8 +161,8 @@ pub fn main() !void {
                 model_shader.updateUniformMatrix("u_normal_matrix", &.{zm.identity()});
                 floor.draw(model_shader);
 
-                // animateRobot(&frame_counter, robot);
-                robot.draw(model_shader);
+                try robot.animate(@floatCast(delta_time));
+                try robot.draw(model_shader);
             },
             .fish => {},
         }
@@ -233,125 +203,207 @@ fn initFloor(textures: ?[]const Texture) Mesh {
 }
 
 fn initRobot(allocator: std.mem.Allocator, textures: ?[]const Texture) !Model {
-    // var meshes = try std.ArrayList(Mesh).initCapacity(allocator, 14);
-    // var translations = try std.ArrayList(Mat).initCapacity(allocator, 14);
-
     var shape = Shape.initCube();
     defer shape.deinit();
 
     shape.unweld();
     shape.computeNormals();
     shape.translate(-0.5, -1, -0.5);
-    // shape.rotate(std.math.degreesToRadians(180), 1, 0, 0);
-
-    // var foot = shape.clone();
-    // defer foot.deinit();
-    // foot.scale(0.1, 0.025, 0.15);
-    // meshes.appendNTimesAssumeCapacity(Mesh.initShape(foot, textures, .triangles), 2);
-    // translations.appendAssumeCapacity(zm.translation(-0.07, 0.025, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.07, 0.025, 0));
-
-    // var leg = shape.clone();
-    // defer leg.deinit();
-    // leg.scale(0.08, 0.2, 0.08);
-    // meshes.appendNTimesAssumeCapacity(Mesh.initShape(leg, textures, .triangles), 4);
-    // translations.appendAssumeCapacity(zm.translation(-0.07, 0.225, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.07, 0.225, 0));
-    // translations.appendAssumeCapacity(zm.translation(-0.07, 0.425, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.07, 0.425, 0));
-
-    // var arm = shape.clone();
-    // defer arm.deinit();
-    // arm.scale(0.08, 0.2, 0.08);
-    // meshes.appendNTimesAssumeCapacity(Mesh.initShape(arm, textures, .triangles), 4);
-    // translations.appendAssumeCapacity(zm.translation(-0.3 / 2.0 - 0.04, 0.225 + 0.4, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.3 / 2.0 + 0.04, 0.225 + 0.4, 0));
-    // translations.appendAssumeCapacity(zm.translation(-0.3 / 2.0 - 0.04, 0.425 + 0.4, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.3 / 2.0 + 0.04, 0.425 + 0.4, 0));
-
-    // var hand = shape.clone();
-    // defer hand.deinit();
-    // hand.scale(0.025, 0.08, 0.07);
-    // meshes.appendNTimesAssumeCapacity(Mesh.initShape(hand, textures, .triangles), 2);
-    // translations.appendAssumeCapacity(zm.translation(-0.3 / 2.0 - 0.04, 0.425, 0));
-    // translations.appendAssumeCapacity(zm.translation(0.3 / 2.0 + 0.04, 0.425, 0));
 
     var chest = shape.clone();
     defer chest.deinit();
     chest.scale(0.3, 0.4, 0.15);
-    // meshes.appendAssumeCapacity(Mesh.initShape(chest, textures, .triangles));
-    // translations.appendAssumeCapacity(zm.translation(0, 0.425 + 0.4, 0));
-
     var model_data = Tree(Model.JointData).init(
-        .{
-            .mesh = Mesh.initShape(chest, textures, .triangles),
-            .translation = zm.translation(0, 0.425 + 0.4, 0),
-            .rotation = zm.qidentity(),
-        },
+        .init(
+            .initShape(chest, textures, .triangles),
+            zm.translation(0, 0.825, 0),
+            zm.qidentity(),
+            .{ zm.qidentity(), zm.qidentity() },
+        ),
     );
 
     var head = shape.clone();
     defer head.deinit();
     head.scale(0.1, 0.1, 0.1);
+    head.rotate(std.math.degreesToRadians(180), 1, 0, 0);
+    try model_data.root.append(
+        allocator,
+        .init(
+            .initShape(head, textures, .triangles),
+            zm.translation(0, 0, 0),
+            zm.qidentity(),
+            .{
+                zm.quatFromRollPitchYaw(0, -0.5, 0),
+                zm.quatFromRollPitchYaw(0, 0.5, 0),
+            },
+        ),
+    );
 
-    try model_data.root.append(allocator, .{
-        .mesh = Mesh.initShape(head, textures, .triangles),
-        .translation = zm.translation(0, 0.425 + 0.4 + 0.1, 0),
-        .rotation = zm.qidentity(),
-    });
-    // meshes.appendAssumeCapacity(Mesh.initShape(head, textures, .triangles));
-    // translations.appendAssumeCapacity(zm.translation(0, 0.425 + 0.4 + 0.1, 0));
+    var arm = shape.clone();
+    defer arm.deinit();
+    arm.scale(0.08, 0.2, 0.08);
+    var right_arm = try model_data.root.create(
+        allocator,
+        .init(
+            .initShape(arm, textures, .triangles),
+            zm.translation(-0.3 / 2.0 - 0.04, 0, 0),
+            zm.qidentity(),
+            .{
+                zm.quatFromRollPitchYaw(0.6, 0, 0),
+                zm.quatFromRollPitchYaw(-0.6, 0, 0),
+            },
+        ),
+    );
+    right_arm = try right_arm.create(
+        allocator,
+        .init(
+            .initShape(arm, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.quatFromRollPitchYaw(-0.6, 0, 0),
+            .{
+                zm.quatFromRollPitchYaw(0.6, 0, 0),
+                zm.quatFromRollPitchYaw(-0.6, 0, 0),
+            },
+        ),
+    );
 
-    return Model.init(model_data);
+    var left_arm = try model_data.root.create(
+        allocator,
+        .init(
+            .initShape(arm, textures, .triangles),
+            zm.translation(0.3 / 2.0 + 0.04, 0, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+    left_arm = try left_arm.create(
+        allocator,
+        .init(
+            .initShape(arm, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+
+    var hand = shape.clone();
+    defer hand.deinit();
+    hand.scale(0.025, 0.08, 0.07);
+    try right_arm.append(
+        allocator,
+        .init(
+            .initShape(hand, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+    try left_arm.append(
+        allocator,
+        .init(
+            .initShape(hand, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+
+    var leg = shape.clone();
+    defer leg.deinit();
+    leg.scale(0.08, 0.2, 0.08);
+    var right_leg = try model_data.root.create(
+        allocator,
+        .init(
+            .initShape(leg, textures, .triangles),
+            zm.translation(-0.07, -0.4, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+    right_leg = try right_leg.create(
+        allocator,
+        .init(
+            .initShape(leg, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+
+    var left_leg = try model_data.root.create(
+        allocator,
+        .init(
+            .initShape(leg, textures, .triangles),
+            zm.translation(0.07, -0.4, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+    left_leg = try left_leg.create(
+        allocator,
+        .init(
+            .initShape(leg, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+
+    var foot = shape.clone();
+    defer foot.deinit();
+    foot.scale(0.1, 0.025, 0.15);
+    try right_leg.append(
+        allocator,
+        .init(
+            .initShape(foot, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+    try left_leg.append(
+        allocator,
+        .init(
+            .initShape(foot, textures, .triangles),
+            zm.translation(0, -0.2, 0),
+            zm.qidentity(),
+            .{
+                zm.qidentity(),
+                zm.qidentity(),
+            },
+        ),
+    );
+
+    return try Model.init(model_data);
 }
 
-// fn initRobot(allocator: std.mem.Allocator, textures: ?[]const Texture) Model {
-//     var shape = Shape.initCube();
-//     defer shape.deinit();
-
-//     shape.unweld();
-//     shape.computeNormals();
-//     shape.translate(-0.5, -1, -0.5);
-
-//     var chest = shape.clone();
-//     defer chest.deinit();
-//     chest.scale(0.3, 0.4, 0.15);
-
-//     var model_data = Tree(Model.JointData).init(.{
-//         .mesh = Mesh.initShape(chest, textures, .triangles),
-//         .translation = zm.translation(0, 0.425 + 0.4, 0),
-//         .rotation = zm.qidentity(),
-//     });
-
-//     var head = shape.clone();
-//     defer head.deinit();
-//     head.scale(0.1, 0.1, 0.1);
-
-//     try model_data.root.append(allocator, .{
-//         .mesh = Mesh.initShape(head, textures, .triangles),
-//         .translation = zm.translation(0, 0.425 + 0.4 + 0.1, 0),
-//         .rotation = zm.qidentity(),
-//     });
-
-//     return Model.init(model_data);
-// }
-
-// fn animateRobot(frame_counter: *u16, robot: Model) void {
-//     if (frame_counter.* > robot.animation_frames) {
-//         robot.translations.items[2] = zm.mul(zm.rotationX(-std.math.degreesToRadians(1)), robot.translations.items[2]);
-//         robot.translations.items[3] = zm.mul(zm.rotationX(-std.math.degreesToRadians(1)), robot.translations.items[3]);
-//     } else {
-//         robot.translations.items[2] = zm.mul(zm.rotationX(std.math.degreesToRadians(1)), robot.translations.items[2]);
-//         robot.translations.items[3] = zm.mul(zm.rotationX(std.math.degreesToRadians(1)), robot.translations.items[3]);
-//     }
-
-//     frame_counter.* += 1;
-
-//     if (frame_counter.* > robot.animation_frames * 2) {
-//         frame_counter.* = 0;
-//     }
-// }
-
 fn drawGui(light_ubo: zgl.Buffer, light_shader: gl_helper.Shader, light_color: *zm.Vec) void {
     if (app_state.render_gui) {
         zgui.backend.newFrame(@intCast(app_state.width), @intCast(app_state.height));

src/tree.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
+const ArrayList = std.ArrayList;
 
 pub fn Tree(comptime T: type) type {
     return struct {
@@ -7,91 +8,210 @@ pub fn Tree(comptime T: type) type {
 
         root: Node,
 
-        const Children = std.ArrayList(Node);
+        const Children = ArrayList(Node);
         const Node = struct {
             val: T,
-            parent: ?*Node,
-            index: usize,
-            children: std.ArrayList(Node),
+            children: ArrayList(Node),
 
-            pub fn init(val: T, parent: ?*Node, index: usize) Node {
+            pub fn init(val: T) Node {
                 return .{
                     .val = val,
                     .children = .empty,
-                    .parent = parent,
-                    .index = index,
                 };
             }
 
             pub fn append(self: *Node, allocator: Allocator, val: T) !void {
-                const child = Node.init(val, self, self.children.items.len);
+                const child = Node.init(val);
                 try self.children.append(allocator, child);
             }
+
+            pub fn create(self: *Node, allocator: Allocator, val: T) !*Node {
+                const child = Node.init(val);
+                try self.children.append(allocator, child);
+                return &self.children.items[self.children.items.len - 1];
+            }
         };
 
         pub fn init(val: T) @This() {
-            return .{ .root = .init(val, null, 0) };
+            return .{ .root = .init(val) };
         }
 
-        pub const DepthFirstIterator = struct {
-            const State = enum {
-                GoDeeper,
-                GoBroader,
-            };
-            tree: *Tree(T),
-            current: ?*Node,
-            state: State,
+        pub const PreOrderIterator = struct {
+            pre_order: ArrayList(*Node),
+            index: usize,
 
-            pub fn init(tree: *Tree(T)) DepthFirstIterator {
-                return DepthFirstIterator{
-                    .tree = tree,
-                    .current = &tree.root,
-                    .state = State.GoDeeper,
+            pub fn init(tree: *Tree(T), allocator: Allocator) !PreOrderIterator {
+                var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+                defer arena.deinit();
+                const arena_allocator = arena.allocator();
+
+                var stack = try ArrayList(*Node).initCapacity(arena_allocator, 1);
+                stack.appendAssumeCapacity(&tree.root);
+
+                var pre_order = ArrayList(*Node).empty;
+
+                while (stack.items.len > 0) {
+                    if (stack.pop()) |tmp| {
+                        try pre_order.insert(allocator, 0, tmp);
+
+                        for (0..tmp.children.items.len) |i| {
+                            try stack.append(arena_allocator, &tmp.children.items[i]);
+                        }
+                    }
+                }
+
+                return .{
+                    .index = 0,
+                    .pre_order = pre_order,
                 };
             }
 
-            pub fn next(it: *DepthFirstIterator) ?*Node {
-                // State machine
-                while (it.current) |current| {
-                    switch (it.state) {
-                        State.GoDeeper => {
-                            // Follow child node until deepest possible level
-                            if (current.children.items.len > 0) {
-                                it.current = &current.children.items[0];
-                            } else {
-                                it.state = State.GoBroader;
-                                return current;
-                            }
-                        },
-                        State.GoBroader => {
-                            if (current.parent) |parent| {
-                                if (parent.children.items.len - 1 > (current.index)) {
-                                    it.current = &parent.children.items[current.index + 1];
-                                    it.state = .GoDeeper;
-                                } else {
-                                    it.current = current.parent;
-                                    return current.parent;
-                                }
-                            } else {
-                                return null;
-                            }
-                        },
-                    }
+            pub fn next(it: *PreOrderIterator) ?*Node {
+                while (it.index < it.pre_order.items.len) {
+                    const val = it.pre_order.items[it.index];
+                    it.index += 1;
+                    return val;
                 }
                 return null;
             }
 
-            pub fn reset(it: *DepthFirstIterator) void {
-                it.current = it.tree.root;
+            pub fn deinit(self: *PreOrderIterator, allocator: Allocator) void {
+                self.pre_order.deinit(allocator);
             }
         };
 
-        pub fn depthFirstIterator(tree: *@This()) DepthFirstIterator {
-            return DepthFirstIterator.init(tree);
+        pub fn preOrderIterator(tree: *@This(), allocator: Allocator) !PreOrderIterator {
+            return PreOrderIterator.init(tree, allocator);
         }
 
-        pub fn deinit(self: *@This(), allocator: Allocator) void {
-            var iterator = self.depthFirstIterator();
+        pub const PostOrderIterator = struct {
+            post_order: ArrayList(*Node),
+            index: usize,
+
+            const Frame = struct {
+                node: *Node,
+                children_index: usize,
+            };
+
+            pub fn init(tree: *Tree(T), allocator: Allocator) !PostOrderIterator {
+                var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+                defer arena.deinit();
+                const arena_allocator = arena.allocator();
+
+                var stack = ArrayList(Frame).empty;
+                var current_root_index: usize = 0;
+                var post_order = ArrayList(*Node).empty;
+
+                var curr_node: ?*Node = &tree.root;
+                while (curr_node != null or stack.items.len > 0) {
+                    if (curr_node) |cur| {
+                        try stack.append(arena_allocator, .{
+                            .children_index = current_root_index,
+                            .node = cur,
+                        });
+
+                        if (cur.children.items.len >= 1) {
+                            curr_node = &cur.children.items[0];
+                        } else {
+                            curr_node = null;
+                        }
+                        continue;
+                    }
+
+                    if (stack.pop()) |tmp| {
+                        try post_order.append(allocator, tmp.node);
+
+                        while (stack.items.len > 0 and tmp.children_index == stack.items[stack.items.len - 1].node.children.items.len - 1) {
+                            if (stack.pop()) |tmp2| {
+                                try post_order.append(allocator, tmp2.node);
+                            }
+                        }
+
+                        if (stack.items.len > 0 and stack.items[stack.items.len - 1].node.children.items.len > tmp.children_index + 1) {
+                            curr_node = &stack.items[stack.items.len - 1].node.children.items[tmp.children_index + 1];
+                            current_root_index = tmp.children_index + 1;
+                        }
+                    }
+                }
+
+                return .{
+                    .index = 0,
+                    .post_order = post_order,
+                };
+            }
+
+            pub fn next(it: *PostOrderIterator) ?*Node {
+                while (it.index < it.post_order.items.len) {
+                    const val = it.post_order.items[it.index];
+                    it.index += 1;
+                    return val;
+                }
+                return null;
+            }
+
+            pub fn deinit(self: *PostOrderIterator, allocator: Allocator) void {
+                self.post_order.deinit(allocator);
+            }
+        };
+
+        pub fn postOrderIterator(tree: *@This(), allocator: Allocator) !PostOrderIterator {
+            return PostOrderIterator.init(tree, allocator);
+        }
+
+        pub const LevelOrderIterator = struct {
+            level_order: ArrayList(*Node),
+            index: usize,
+
+            pub fn init(tree: *Tree(T), allocator: Allocator) !LevelOrderIterator {
+                var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+                defer arena.deinit();
+                const arena_allocator = arena.allocator();
+
+                var stack = try ArrayList(*Node).initCapacity(arena_allocator, 1);
+                stack.appendAssumeCapacity(&tree.root);
+
+                var level_order = ArrayList(*Node).empty;
+
+                while (stack.items.len > 0) {
+                    if (stack.pop()) |tmp| {
+                        try level_order.append(allocator, tmp);
+
+                        for (0..tmp.children.items.len) |i| {
+                            try stack.append(arena_allocator, &tmp.children.items[i]);
+                        }
+                    }
+                }
+
+                return .{
+                    .index = 0,
+                    .level_order = level_order,
+                };
+            }
+
+            pub fn next(it: *LevelOrderIterator) ?*Node {
+                while (it.index < it.level_order.items.len) {
+                    const val = it.level_order.items[it.index];
+                    it.index += 1;
+                    return val;
+                }
+                return null;
+            }
+
+            pub fn deinit(self: *LevelOrderIterator, allocator: Allocator) void {
+                self.level_order.deinit(allocator);
+            }
+        };
+
+        pub fn levelOrderIterator(tree: *@This(), allocator: Allocator) !LevelOrderIterator {
+            return LevelOrderIterator.init(tree, allocator);
+        }
+
+        pub fn deinit(self: *@This(), allocator: Allocator) !void {
+            var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+            defer arena.deinit();
+            const arena_allocator = arena.allocator();
+
+            var iterator = try self.postOrderIterator(arena_allocator);
             while (iterator.next()) |node| {
                 node.children.deinit(allocator);
             }
@@ -131,20 +251,17 @@ test "Tree" {
     const UTree = Tree(u16);
 
     var tree = UTree.init(10);
-    defer tree.deinit(allocator);
+    defer tree.deinit(allocator) catch {};
 
     try tree.root.append(allocator, 20);
     try tree.root.append(allocator, 500);
 
-    var iterator = tree.depthFirstIterator();
+    try tree.root.children.items[1].append(allocator, 999);
+
+    var iterator = try tree.levelOrderIterator(allocator);
+    defer iterator.deinit(allocator);
     std.debug.print("\n", .{});
     while (iterator.next()) |node| {
-        var accumulator: u32 = node.val;
-        var current = node;
-        while (current.parent) |parent| {
-            accumulator *= parent.val;
-            current = parent;
-        }
-        std.debug.print("Val: {} Acc: {}\n", .{ node.val, accumulator });
+        std.debug.print("Val: {}\n", .{node.val});
     }
 }