GUI: Box drawing

assets/shaders/gui_box.frag

@@ -0,0 +1,39 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+in Varyings {
+    layout(location = 0) flat uint instance;
+    layout(location = 1) vec2 positionSSPX;
+} var;
+
+#include "includes/gui_box_common.glsl"
+
+layout(location = 0) out vec4 fragColor;
+
+float boxSDF(vec2 p, vec2 center, vec2 halfExtents, float borderRadius) {
+    vec2 q = abs(p - center) - halfExtents + borderRadius;
+    return min(max(q.x, q.y), 0.0) + length(max(q, 0.0)) - borderRadius;
+}
+
+#define BOX _Boxes[var.instance]
+
+void main() {
+    vec2 halfExtentsPX = 0.5 * BOX.sizePX;
+    vec2 centerSSPX = BOX.positionSSPX + halfExtentsPX;
+    float borderHalfWidthPX = 0.5 * BOX.borderWidthPX;
+
+    float interiorSDF = boxSDF(var.positionSSPX, centerSSPX, halfExtentsPX, BOX.borderRadiusPX) + BOX.borderWidthPX;
+    float borderSDF = abs(interiorSDF - borderHalfWidthPX) - borderHalfWidthPX;
+
+    float interiorCoverage = clamp(-interiorSDF + 0.5, 0.0, 1.0) * BOX.backgroundColor.a;
+    float borderCoverage = clamp(-borderSDF + 0.5, 0.0, 1.0) * BOX.borderColor.a;
+    float totalCoverage = interiorCoverage + borderCoverage;
+
+    fragColor = vec4(
+        interiorCoverage * BOX.backgroundColor.rgb +
+        borderCoverage * BOX.borderColor.rgb,
+        totalCoverage
+    );
+}

assets/shaders/gui_box.vert

@@ -0,0 +1,30 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+out Varyings {
+    layout(location = 0) flat uint instance;
+    layout(location = 1) vec2 positionSSPX;
+} var;
+
+#include "includes/gui_box_common.glsl"
+
+const vec2 VERTICES[4] = vec2[](
+    vec2(0, 1),
+    vec2(1, 1),
+    vec2(0, 0),
+    vec2(1, 0)
+);
+
+#define BOX _Boxes[gl_InstanceIndex]
+#define VERTEX VERTICES[gl_VertexIndex]
+
+void main() {
+    vec2 positionSSPX = VERTEX * BOX.sizePX + BOX.positionSSPX;
+    vec4 positionCS = vec4(_Global.matrixSSPXtoCS * vec3(positionSSPX, 1.0), 0.0, 1.0);
+
+    gl_Position = positionCS;
+    var.instance = gl_InstanceIndex;
+    var.positionSSPX = positionSSPX;
+}

assets/shaders/gui_image.frag

@@ -0,0 +1,20 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+in Varyings {
+    layout(location = 0) flat uint instance;
+    layout(location = 1) vec2 texCoord;
+} var;
+
+#include "includes/gui_image_common.glsl"
+
+layout(location = 0) out vec4 fragColor;
+
+#define IMAGE _Images[var.instance]
+
+void main() {
+    vec4 texel = texture(sampler2D(_Textures[uint(IMAGE.textureId)], _Sampler), var.texCoord);
+    fragColor = texel * IMAGE.tint;
+}

assets/shaders/gui_image.vert

@@ -0,0 +1,32 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+out Varyings {
+    layout(location = 0) flat uint instance;
+    layout(location = 1) vec2 texCoord;
+} var;
+
+#include "includes/gui_image_common.glsl"
+
+const vec2 VERTICES[4] = vec2[](
+    vec2(0, 1),
+    vec2(1, 1),
+    vec2(0, 0),
+    vec2(1, 0)
+);
+
+#define IMAGE _Images[gl_InstanceIndex]
+#define VERTEX VERTICES[gl_VertexIndex]
+
+void main() {
+    vec2 positionSSPX = VERTEX * IMAGE.sizePX + IMAGE.positionSSPX;
+    vec4 positionCS = vec4(_Global.matrixSSPXtoCS * vec3(positionSSPX, 1.0), 0.0, 1.0);
+
+    vec2 texCoord = VERTEX * (IMAGE.uvMax - IMAGE.uvMin) + IMAGE.uvMin;
+
+    gl_Position = positionCS;
+    var.instance = gl_InstanceIndex;
+    var.texCoord = texCoord;
+}

assets/shaders/gui_text.frag

@@ -0,0 +1,15 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+uint calcRootCode(float y1, float y2, float y3) {
+    uint i1 = floatBitsToUint(y1) >> 31U;
+    uint i2 = floatBitsToUint(y2) >> 30U;
+    uint i3 = floatBitsToUint(y3) >> 29U;
+
+    uint shift = (i2 & 2U) | (i1 & ~2U);
+    shift = (i3 & 4U) | (shift & ~4U);
+
+    return ((0x2E74U >> shift) & 0x0101U);
+}

assets/shaders/gui_text.vert

@@ -0,0 +1,10 @@
+#version 460
+#extension GL_EXT_nonuniform_qualifier : require
+#extension GL_EXT_scalar_block_layout : require
+#extension GL_EXT_shader_16bit_storage : require
+
+layout(location = 0) in vec4 positionOS_normalOS;
+layout(location = 1) in vec4 texCoordEM_band_flags;
+layout(location = 2) in vec4 jacobian;
+layout(location = 3) in vec4 scale_offset;
+layout(location = 4) in vec4 color;

assets/shaders/includes/global_uniforms.glsl

@@ -0,0 +1,6 @@
+layout(set = 0, binding = 0, scalar) uniform GlobalUniforms {
+    mat4 matrixWStoVS;
+    mat4 matrixVStoCS;
+    mat3x2 matrixSSPXtoCS;
+    vec3 ambientLight;
+} _Global;

assets/shaders/includes/gui_box_common.glsl

@@ -0,0 +1,14 @@
+struct Box {
+    vec4 backgroundColor;
+    vec4 borderColor;
+    vec2 positionSSPX;
+    vec2 sizePX;
+    float borderWidthPX;
+    float borderRadiusPX;
+};
+
+#include "global_uniforms.glsl"
+
+layout(set = 0, binding = 1, scalar) readonly buffer Boxes {
+    Box _Boxes[];
+};

assets/shaders/includes/gui_image_common.glsl

@@ -0,0 +1,17 @@
+struct Image {
+    vec4 tint;
+    vec2 positionSSPX;
+    vec2 sizePX;
+    vec2 uvMin;
+    vec2 uvMax;
+    uint16_t textureId;
+};
+
+#include "global_uniforms.glsl"
+
+layout(set = 0, binding = 1, scalar) readonly buffer Images {
+    Image _Images[];
+};
+
+layout(set = 0, binding = 2) uniform sampler _Sampler;
+layout(set = 0, binding = 3) uniform texture2D _Textures[];

assets/shaders/includes/main_common.glsl

@@ -32,11 +32,7 @@ struct ObjectUniforms {
     uint16_t material;
 };
 
-layout(set = 0, binding = 0, scalar) uniform GlobalUniforms {
-    mat4 matrixWStoVS;
-    mat4 matrixVStoCS;
-    vec3 ambientLight;
-} _Global;
+#include "global_uniforms.glsl"
 
 layout(set = 0, binding = 1, scalar) readonly buffer PointLights {
     uint count;

assets/shaders/includes/tone_mapping.glsl

@@ -0,0 +1,8 @@
+vec3 toneMapAcesNarkowicz(vec3 color) {
+    const float A = 2.51;
+    const float B = 0.03;
+    const float C = 2.43;
+    const float D = 0.59;
+    const float E = 0.14;
+    return clamp((color * (A * color + B)) / (color * (C * color + D) + E), 0.0, 1.0);
+}

assets/shaders/main.frag

@@ -12,7 +12,8 @@ in Varyings {
     layout(location = 5) vec3 bitangentVS;
 } var;
 
-#include "main_common.glsl"
+#include "includes/main_common.glsl"
+#include "includes/tone_mapping.glsl"
 
 layout(location = 0) out vec4 fragColor;
 
@@ -39,15 +40,6 @@ float distributionGGX(float dotNH, float alpha) {
     return alphaSquared * INV_PI / (tmp * tmp);
 }
 
-vec3 toneMapAcesNarkowicz(vec3 color) {
-    const float A = 2.51;
-    const float B = 0.03;
-    const float C = 2.43;
-    const float D = 0.59;
-    const float E = 0.14;
-    return clamp((color * (A * color + B)) / (color * (C * color + D) + E), 0.0, 1.0);
-}
-
 vec3 lightOutgoingRadiance(
     vec3 viewDirectionVS, vec3 normalVS, float dotNV,
     vec3 baseColor, float alpha, float metallic, vec3 f0,

assets/shaders/main.vert

@@ -17,7 +17,7 @@ out Varyings {
     layout(location = 5) vec3 bitangentVS;
 } var;
 
-#include "main_common.glsl"
+#include "includes/main_common.glsl"
 
 #define OBJECT _Object[gl_InstanceIndex]
 

assets/shaders/skybox.frag

@@ -9,14 +9,7 @@ layout(set = 0, binding = 2) uniform textureCube _Texture;
 
 layout(location = 0) out vec4 fragColor;
 
-vec3 toneMapAcesNarkowicz(vec3 color) {
-    const float A = 2.51;
-    const float B = 0.03;
-    const float C = 2.43;
-    const float D = 0.59;
-    const float E = 0.14;
-    return clamp((color * (A * color + B)) / (color * (C * color + D) + E), 0.0, 1.0);
-}
+#include "includes/tone_mapping.glsl"
 
 void main() {
     vec4 texel = texture(samplerCube(_Texture, _Sampler), var.texCoord);

assets/shaders/skybox.vert

@@ -7,11 +7,7 @@ out Varyings {
     layout(location = 0) vec3 texCoord;
 } var;
 
-layout(set = 0, binding = 0, scalar) uniform GlobalUniforms {
-    mat4 matrixWStoVS;
-    mat4 matrixVStoCS;
-    vec3 ambientLight;
-} _Global;
+#include "includes/global_uniforms.glsl"
 
 void main() {
     vec3 directionVS = (_Global.matrixWStoVS * vec4(directionWS, 0.0)).xyz;

build.zig

@@ -10,11 +10,22 @@ pub fn build(b: *std.Build) !void {
     const media_dep = b.dependency("media", .{
         .target = target,
     });
+
     const vecmath_dep = b.dependency("vecmath", .{
         .target = target,
     });
-    const vulkan_dep = b.dependency("vulkan_zig", .{ .registry = b.path("vendor/vk.xml") });
-    const zglfw_dep = b.dependency("zglfw", .{ .import_vulkan = true });
+
+    const vulkan_dep = b.dependency("vulkan_zig", .{
+        .target = target,
+        .optimize = optimize,
+        .registry = b.path("vendor/vk.xml"),
+    });
+
+    const zglfw_dep = b.dependency("zglfw", .{
+        .target = target,
+        .optimize = optimize,
+        .import_vulkan = true,
+    });
 
     const media_mod = media_dep.module("media");
     const vecmath_mod = vecmath_dep.module("vecmath");

compile_shaders.sh

@@ -1,7 +1,9 @@
 #!/bin/sh
 
-glslc --target-env=vulkan1.2 assets/shaders/equirect_to_cube.comp -o src/shaders/equirect_to_cube_comp.spv
-glslc --target-env=vulkan1.2 assets/shaders/main.frag -o src/shaders/main_frag.spv
-glslc --target-env=vulkan1.2 assets/shaders/main.vert -o src/shaders/main_vert.spv
-glslc --target-env=vulkan1.2 assets/shaders/skybox.frag -o src/shaders/skybox_frag.spv
-glslc --target-env=vulkan1.2 assets/shaders/skybox.vert -o src/shaders/skybox_vert.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/equirect_to_cube.comp -o src/shaders/equirect_to_cube_comp.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/gui_box.frag -o src/shaders/gui_box_frag.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/gui_box.vert -o src/shaders/gui_box_vert.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/main.frag -o src/shaders/main_frag.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/main.vert -o src/shaders/main_vert.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/skybox.frag -o src/shaders/skybox_frag.spv
+glslc -g --target-env=vulkan1.2 assets/shaders/skybox.vert -o src/shaders/skybox_vert.spv

src/Game.zig

@@ -15,6 +15,7 @@ const Chunk = @import("assets/Chunk.zig");
 const Chunks = @import("Chunks.zig");
 const CommandBuffer = @import("engine/CommandBuffer.zig");
 const Engine = @import("engine/Engine.zig");
+const Gui = @import("Gui.zig");
 const Iterator2 = math.Iterator2;
 const Materials = @import("assets/Materials.zig");
 const Player = @import("Player.zig");
@@ -51,6 +52,7 @@ materials: Materials,
 textures: Textures,
 chunks: Chunks,
 skybox: Skybox,
+gui: Gui,
 
 player: Player,
 
@@ -164,7 +166,7 @@ pub fn init(allocator: std.mem.Allocator, io: std.Io, engine: *Engine, swapchain
         },
     });
     errdefer engine.destroyPipelineLayout(pipeline_layout);
-    engine.setObjectName(pipeline_layout, "PL", .{});
+    engine.setObjectName(pipeline_layout, "PL Main", .{});
 
     const vertex_shader = try engine.createShaderModule(.{ .code = &shaders.main_vert_spv });
     defer engine.destroyShaderModule(vertex_shader);
@@ -403,7 +405,7 @@ pub fn init(allocator: std.mem.Allocator, io: std.Io, engine: *Engine, swapchain
         .subpass = 0,
     });
     errdefer engine.destroyPipeline(pipeline);
-    engine.setObjectName(pipeline, "P", .{});
+    engine.setObjectName(pipeline, "P Main", .{});
 
     const descriptor_pool = try engine.createDescriptorPool(.{
         .flags = .{
@@ -430,7 +432,7 @@ pub fn init(allocator: std.mem.Allocator, io: std.Io, engine: *Engine, swapchain
         },
     });
     errdefer engine.destroyDescriptorPool(descriptor_pool);
-    engine.setObjectName(descriptor_pool, "DP", .{});
+    engine.setObjectName(descriptor_pool, "DP Main", .{});
 
     const global_descriptor_set = try engine.allocateDescriptorSet(.{
         .descriptor_pool = descriptor_pool,
@@ -645,6 +647,14 @@ pub fn init(allocator: std.mem.Allocator, io: std.Io, engine: *Engine, swapchain
     );
     errdefer skybox.deinit(engine);
 
+    var gui = try Gui.init(
+        allocator,
+        engine,
+        global_uniforms.buffer,
+        swapchain.render_pass,
+    );
+    errdefer gui.deinit(engine, allocator);
+
     return .{
         .allocator = allocator,
         .io = io,
@@ -674,6 +684,7 @@ pub fn init(allocator: std.mem.Allocator, io: std.Io, engine: *Engine, swapchain
         .textures = textures,
         .chunks = .{ .chunks = chunks },
         .skybox = skybox,
+        .gui = gui,
 
         .player = .init(player_position_sv, 0, 0),
     };
@@ -692,6 +703,7 @@ pub fn deinit(self: *Game) void {
 
     self.chunks.deinit(self.engine, self.descriptor_pool, self.allocator);
     self.skybox.deinit(self.engine);
+    self.gui.deinit(self.engine, self.allocator);
 
     self.global_uniforms.deinit(self.engine);
     self.global_uniforms_staging_buffer.deinit(self.engine);
@@ -718,8 +730,36 @@ pub fn deinit(self: *Game) void {
 }
 
 pub fn update(self: *Game, dt: f32) void {
+    self.gui.beginFrame();
     self.player.update(dt, &self.chunks);
 
+    const extent = self.swapchain.extent;
+    const framebuffer_size = vm.Vector2.init(
+        @floatFromInt(extent.width),
+        @floatFromInt(extent.height),
+    );
+
+    const crosshair_half_extent_px = 8;
+    const crosshair_half_width_px = 1;
+
+    self.gui.pushBox(.{
+        .background_color = .init(1, 1, 1, 0.5),
+        .border_color = .init(0, 0, 0, 1),
+        .position_sspx = framebuffer_size.mulScalar(0.5).add(.init(-crosshair_half_extent_px, -crosshair_half_width_px)),
+        .size_px = .init(2.0 * crosshair_half_extent_px, 2.0 * crosshair_half_width_px),
+        .border_width_px = 0,
+        .border_radius_px = 0,
+    });
+
+    self.gui.pushBox(.{
+        .background_color = .init(1, 1, 1, 0.5),
+        .border_color = .init(0, 0, 0, 1),
+        .position_sspx = framebuffer_size.mulScalar(0.5).add(.init(-crosshair_half_width_px, -crosshair_half_extent_px)),
+        .size_px = .init(2.0 * crosshair_half_width_px, 2.0 * crosshair_half_extent_px),
+        .border_width_px = 0,
+        .border_radius_px = 0,
+    });
+
     self.render() catch |err| {
         std.log.err("Failed to render: {s}", .{@errorName(err)});
         @panic("Frame update failed");
@@ -807,11 +847,20 @@ fn render(self: *Game) !void {
     );
     // zig fmt: on
 
+    // zig fmt: off
+    const matrix_sspx_to_cs = vm.Matrix3x2.init(
+        2.0 / framebuffer_size.x,  0,
+        0,                         2.0 / framebuffer_size.y,
+        -1,                       -1,
+    );
+    // zig fmt: on
+
     const ambient_light = vm.Vector3.init(0.01, 0.01, 0.01);
 
     const global_uniforms_data: shaders.GlobalUniforms = .{
         .matrixWStoVS = matrix_ws_to_vs,
         .matrixVStoCS = matrix_vs_to_cs,
+        .matrixSSPXtoCS = matrix_sspx_to_cs,
         .ambientLight = ambient_light,
     };
 
@@ -887,6 +936,8 @@ fn render(self: *Game) !void {
             },
         });
 
+        // --- SUBPASS 0 (MAIN) ---
+
         command_buffer.bindPipeline(.graphics, self.pipeline);
         try command_buffer.bindVertexBuffers(0, &.{
             .{
@@ -902,8 +953,13 @@ fn render(self: *Game) !void {
             chunk.draw(self.pipeline_layout, command_buffer);
         }
 
-        try self.skybox.bind(command_buffer, extent);
-        self.skybox.draw(command_buffer);
+        try self.skybox.draw(command_buffer);
+
+        // --- SUBPASS 1 (GUI) ---
+
+        command_buffer.nextSubpass(.@"inline");
+
+        try self.gui.draw(self.engine, command_buffer);
     }
     try command_buffer.endCommandBuffer();
 

src/Gui.zig

@@ -0,0 +1,427 @@
+const Gui = @This();
+const std = @import("std");
+
+const shaders = @import("shaders.zig");
+const vk = @import("vulkan");
+const vm = @import("vecmath");
+
+const CommandBuffer = @import("engine/CommandBuffer.zig");
+const Engine = @import("engine/Engine.zig");
+const GenericBuffer = @import("engine/GenericBuffer.zig").GenericBuffer;
+const Swapchain = @import("engine/Swapchain.zig");
+const Textures = @import("assets/Textures.zig");
+
+pub const Draw = struct {
+    pub const Box = extern struct {
+        background_color: vm.Vector4,
+        border_color: vm.Vector4,
+        position_sspx: vm.Vector2,
+        size_px: vm.Vector2,
+        border_width_px: f32,
+        border_radius_px: f32,
+    };
+
+    pub const Text = extern struct {
+        color: vm.Vector4,
+        pos_min: vm.Vector2,
+        pos_max: vm.Vector2,
+        uv_min: vm.Vector2,
+        uv_max: vm.Vector2,
+        atlas_id: Textures.Id,
+    };
+
+    pub const Image = extern struct {
+        tint: vm.Vector4,
+        position_sspx: vm.Vector2,
+        size_px: vm.Vector2,
+        uv_min: vm.Vector2,
+        uv_max: vm.Vector2,
+        texture_id: Textures.Id,
+    };
+};
+
+pub const Batch = struct {
+    draw_type: std.meta.DeclEnum(Draw),
+    first_instance: u32,
+    instance_count: u32,
+};
+
+box_gpu_buffer: GenericBuffer(void, Draw.Box),
+text_gpu_buffer: GenericBuffer(void, Draw.Text),
+image_gpu_buffer: GenericBuffer(void, Draw.Image),
+
+box_cpu_buffer: std.ArrayList(Draw.Box),
+text_cpu_buffer: std.ArrayList(Draw.Text),
+image_cpu_buffer: std.ArrayList(Draw.Image),
+
+batches: std.ArrayList(Batch),
+
+sampler: vk.Sampler,
+index_buffer: shaders.IndexBuffer,
+
+box_descriptor_set_layout: vk.DescriptorSetLayout,
+box_pipeline_layout: vk.PipelineLayout,
+box_pipeline: vk.Pipeline,
+
+descriptor_pool: vk.DescriptorPool,
+box_descriptor_set: vk.DescriptorSet,
+
+pub const max_box_draws = 1024;
+pub const max_image_draws = 1024;
+pub const max_text_draws = 4096;
+
+pub const max_batches = 1024;
+
+pub fn init(
+    allocator: std.mem.Allocator,
+    engine: *Engine,
+    global_uniforms_buffer: vk.Buffer,
+    render_pass: vk.RenderPass,
+) !Gui {
+    var box_gpu_buffer: GenericBuffer(void, Draw.Box) = try .init(engine, .{
+        .usage = .storage,
+        .target_queue = .graphics,
+        .array_capacity = max_box_draws,
+        .name = "GUI box draws",
+    });
+    errdefer box_gpu_buffer.deinit(engine);
+
+    var text_gpu_buffer: GenericBuffer(void, Draw.Text) = try .init(engine, .{
+        .usage = .storage,
+        .target_queue = .graphics,
+        .array_capacity = max_text_draws,
+        .name = "GUI text draws",
+    });
+    errdefer text_gpu_buffer.deinit(engine);
+
+    var image_gpu_buffer: GenericBuffer(void, Draw.Image) = try .init(engine, .{
+        .usage = .storage,
+        .target_queue = .graphics,
+        .array_capacity = max_image_draws,
+        .name = "GUI image draws",
+    });
+    errdefer image_gpu_buffer.deinit(engine);
+
+    var box_cpu_buffer: std.ArrayList(Draw.Box) = try .initCapacity(allocator, max_box_draws);
+    errdefer box_cpu_buffer.deinit(allocator);
+
+    var text_cpu_buffer: std.ArrayList(Draw.Text) = try .initCapacity(allocator, max_text_draws);
+    errdefer text_cpu_buffer.deinit(allocator);
+
+    var image_cpu_buffer: std.ArrayList(Draw.Image) = try .initCapacity(allocator, max_image_draws);
+    errdefer image_cpu_buffer.deinit(allocator);
+
+    var batches: std.ArrayList(Batch) = try .initCapacity(allocator, max_batches);
+    errdefer batches.deinit(allocator);
+
+    const sampler = try engine.createSampler(.{
+        .mag_filter = .linear,
+        .min_filter = .linear,
+        .mipmap_mode = .linear,
+        .address_mode_u = .repeat,
+        .address_mode_v = .repeat,
+        .address_mode_w = .repeat,
+        .mip_lod_bias = 0,
+        .anisotropy_enable = .false,
+        .max_anisotropy = 0,
+        .compare_enable = .false,
+        .compare_op = .always,
+        .min_lod = 0,
+        .max_lod = vk.LOD_CLAMP_NONE,
+        .border_color = .float_transparent_black,
+        .unnormalized_coordinates = .false,
+    });
+    errdefer engine.destroySampler(sampler);
+
+    const box_descriptor_set_layout = try engine.createDescriptorSetLayout(.{
+        .bindings = &.{
+            .{
+                .binding = 0,
+                .descriptor_type = .uniform_buffer,
+                .descriptor_count = 1,
+                .stage_flags = .{ .vertex_bit = true, .fragment_bit = true },
+            },
+            .{
+                .binding = 1,
+                .descriptor_type = .storage_buffer,
+                .descriptor_count = 1,
+                .stage_flags = .{ .vertex_bit = true, .fragment_bit = true },
+            },
+        },
+    });
+    errdefer engine.destroyDescriptorSetLayout(box_descriptor_set_layout);
+    engine.setObjectName(box_descriptor_set_layout, "DSL GUI Box", .{});
+
+    const box_pipeline_layout = try engine.createPipelineLayout(.{
+        .set_layouts = &.{
+            box_descriptor_set_layout,
+        },
+    });
+    errdefer engine.destroyPipelineLayout(box_pipeline_layout);
+    engine.setObjectName(box_pipeline_layout, "PL GUI Box", .{});
+
+    const box_vertex_shader = try engine.createShaderModule(.{ .code = &shaders.gui_box_vert_spv });
+    defer engine.destroyShaderModule(box_vertex_shader);
+    engine.setObjectName(box_vertex_shader, "SM gui_box_vert", .{});
+
+    const box_fragment_shader = try engine.createShaderModule(.{ .code = &shaders.gui_box_frag_spv });
+    defer engine.destroyShaderModule(box_fragment_shader);
+    engine.setObjectName(box_fragment_shader, "SM gui_box_frag", .{});
+
+    var index_buffer = try shaders.IndexBuffer.init(engine, .{
+        .usage = .index,
+        .target_queue = .graphics,
+        .array_capacity = 6,
+        .name = "QuadIB",
+    });
+    errdefer index_buffer.deinit(engine);
+    try index_buffer.write(engine, .{
+        .elements = &.{ 0, 1, 2, 2, 1, 3 },
+    });
+
+    const box_pipeline = try engine.createGraphicsPipeline(.{
+        .stages = &.{
+            .{
+                .stage = .{ .vertex_bit = true },
+                .module = box_vertex_shader,
+                .name = "main",
+            },
+            .{
+                .stage = .{ .fragment_bit = true },
+                .module = box_fragment_shader,
+                .name = "main",
+            },
+        },
+        .vertex_input_state = .{},
+        .input_assembly_state = .{
+            .topology = .triangle_list,
+            .primitive_restart_enable = .false,
+        },
+        .viewport_state = .{
+            .viewports = &.{undefined}, // dynamic
+            .scissors = &.{undefined}, // dynamic
+        },
+        .rasterization_state = .{
+            .depth_clamp_enable = .false,
+            .rasterizer_discard_enable = .false,
+            .polygon_mode = .fill,
+            .cull_mode = .{},
+            .front_face = .counter_clockwise,
+            .depth_bias_enable = .false,
+            .depth_bias_constant_factor = 0,
+            .depth_bias_clamp = 0,
+            .depth_bias_slope_factor = 0,
+            .line_width = 1,
+        },
+        .multisample_state = .{
+            .rasterization_samples = .{ .@"1_bit" = true },
+            .sample_shading_enable = .false,
+            .min_sample_shading = 1,
+            .alpha_to_coverage_enable = .false,
+            .alpha_to_one_enable = .false,
+        },
+        .color_blend_state = .{
+            .logic_op_enable = .false,
+            .logic_op = .copy,
+            .attachments = &.{
+                .{
+                    .blend_enable = .true,
+                    .src_color_blend_factor = .one,
+                    .dst_color_blend_factor = .one_minus_src_alpha,
+                    .color_blend_op = .add,
+                    .src_alpha_blend_factor = .one,
+                    .dst_alpha_blend_factor = .one_minus_src_alpha,
+                    .alpha_blend_op = .add,
+                    .color_write_mask = .{
+                        .r_bit = true,
+                        .g_bit = true,
+                        .b_bit = true,
+                        .a_bit = true,
+                    },
+                },
+            },
+            .blend_constants = .{ 0, 0, 0, 0 },
+        },
+        .dynamic_state = .{
+            .dynamic_states = &.{ .viewport, .scissor },
+        },
+        .layout = box_pipeline_layout,
+        .render_pass = render_pass,
+        .subpass = 1,
+    });
+    errdefer engine.destroyPipeline(box_pipeline);
+    engine.setObjectName(box_pipeline, "P GUI Box", .{});
+
+    const descriptor_pool = try engine.createDescriptorPool(.{
+        .max_sets = 1,
+        .pool_sizes = &.{
+            .{
+                .type = .uniform_buffer,
+                .descriptor_count = 1,
+            },
+            .{
+                .type = .storage_buffer,
+                .descriptor_count = 1,
+            },
+        },
+    });
+    errdefer engine.destroyDescriptorPool(descriptor_pool);
+    engine.setObjectName(descriptor_pool, "DP GUI", .{});
+
+    const box_descriptor_set = try engine.allocateDescriptorSet(.{
+        .descriptor_pool = descriptor_pool,
+        .set_layout = box_descriptor_set_layout,
+    });
+    engine.setObjectName(box_descriptor_set, "DS GUI Box", .{});
+
+    try engine.updateDescriptorSets(.{
+        .writes = &.{
+            .{
+                .dst_set = box_descriptor_set,
+                .dst_binding = 0,
+                .dst_array_element = 0,
+                .descriptor_type = .uniform_buffer,
+                .descriptor_infos = .{
+                    .buffer = &.{
+                        .{
+                            .buffer = global_uniforms_buffer,
+                            .offset = 0,
+                            .range = vk.WHOLE_SIZE,
+                        },
+                    },
+                },
+            },
+            .{
+                .dst_set = box_descriptor_set,
+                .dst_binding = 1,
+                .dst_array_element = 0,
+                .descriptor_type = .storage_buffer,
+                .descriptor_infos = .{
+                    .buffer = &.{
+                        .{
+                            .buffer = box_gpu_buffer.buffer,
+                            .offset = 0,
+                            .range = vk.WHOLE_SIZE,
+                        },
+                    },
+                },
+            },
+        },
+    });
+
+    return .{
+        .box_gpu_buffer = box_gpu_buffer,
+        .text_gpu_buffer = text_gpu_buffer,
+        .image_gpu_buffer = image_gpu_buffer,
+
+        .box_cpu_buffer = box_cpu_buffer,
+        .text_cpu_buffer = text_cpu_buffer,
+        .image_cpu_buffer = image_cpu_buffer,
+
+        .batches = batches,
+
+        .sampler = sampler,
+        .index_buffer = index_buffer,
+
+        .box_descriptor_set_layout = box_descriptor_set_layout,
+        .box_pipeline_layout = box_pipeline_layout,
+        .box_pipeline = box_pipeline,
+
+        .descriptor_pool = descriptor_pool,
+        .box_descriptor_set = box_descriptor_set,
+    };
+}
+
+pub fn deinit(self: *Gui, engine: *Engine, allocator: std.mem.Allocator) void {
+    std.log.scoped(.deinit).debug("Deinitializing {*} with {*} and Allocator{{{*},{*}}}", .{ self, engine, allocator.ptr, allocator.vtable });
+
+    engine.destroyDescriptorPool(self.descriptor_pool);
+    engine.destroyPipeline(self.box_pipeline);
+    self.index_buffer.deinit(engine);
+    engine.destroyPipelineLayout(self.box_pipeline_layout);
+    engine.destroyDescriptorSetLayout(self.box_descriptor_set_layout);
+    engine.destroySampler(self.sampler);
+
+    self.batches.deinit(allocator);
+
+    self.image_cpu_buffer.deinit(allocator);
+    self.text_cpu_buffer.deinit(allocator);
+    self.box_cpu_buffer.deinit(allocator);
+
+    self.image_gpu_buffer.deinit(engine);
+    self.text_gpu_buffer.deinit(engine);
+    self.box_gpu_buffer.deinit(engine);
+
+    self.* = undefined;
+}
+
+pub fn beginFrame(self: *Gui) void {
+    self.box_cpu_buffer.clearRetainingCapacity();
+    self.text_cpu_buffer.clearRetainingCapacity();
+    self.image_cpu_buffer.clearRetainingCapacity();
+
+    self.batches.clearRetainingCapacity();
+}
+
+pub fn pushBox(self: *Gui, box: Draw.Box) void {
+    const instance: u32 = @intCast(self.box_cpu_buffer.items.len);
+    self.box_cpu_buffer.appendBounded(box) catch return;
+    self.extendOrAddBatch(.Box, instance);
+}
+
+pub fn pushText(self: *Gui, text: Draw.Text) void {
+    const instance: u32 = @intCast(self.text_cpu_buffer.items.len);
+    self.text_cpu_buffer.appendBounded(text) catch return;
+    self.extendOrAddBatch(.Text, instance);
+}
+
+pub fn pushImage(self: *Gui, image: Draw.Image) void {
+    const instance: u32 = @intCast(self.image_cpu_buffer.items.len);
+    self.image_cpu_buffer.appendBounded(image) catch return;
+    self.extendOrAddBatch(.Image, instance);
+}
+
+fn extendOrAddBatch(self: *Gui, draw_type: std.meta.DeclEnum(Draw), instance: u32) void {
+    if (self.batches.items.len == 0 or self.batches.items[self.batches.items.len - 1].draw_type != draw_type) {
+        self.batches.appendBounded(.{
+            .draw_type = draw_type,
+            .first_instance = instance,
+            .instance_count = 1,
+        }) catch return;
+    } else {
+        const batch = &self.batches.items[self.batches.items.len - 1];
+        std.debug.assert(batch.first_instance + batch.instance_count == instance);
+        batch.instance_count += 1;
+    }
+}
+
+pub fn draw(self: *const Gui, engine: *Engine, command_buffer: CommandBuffer) !void {
+    command_buffer.bindIndexBuffer(self.index_buffer.buffer, 0, .uint16);
+
+    try self.box_gpu_buffer.write(engine, .{ .elements = self.box_cpu_buffer.items });
+    try self.text_gpu_buffer.write(engine, .{ .elements = self.text_cpu_buffer.items });
+    try self.image_gpu_buffer.write(engine, .{ .elements = self.image_cpu_buffer.items });
+
+    for (self.batches.items) |batch| {
+        switch (batch.draw_type) {
+            .Box => {
+                command_buffer.bindPipeline(.graphics, self.box_pipeline);
+                command_buffer.bindDescriptorSet(.graphics, self.box_pipeline_layout, 0, self.box_descriptor_set, null);
+            },
+            .Text => {
+                std.log.warn("GUI Text not implemented; skipping batch", .{});
+                continue;
+            },
+            .Image => {
+                std.log.warn("GUI Image not implemented; skipping batch", .{});
+                continue;
+            },
+        }
+
+        command_buffer.drawIndexed(.{
+            .index_count = 6,
+            .first_instance = batch.first_instance,
+            .instance_count = batch.instance_count,
+        });
+    }
+}

src/engine/CommandBuffer.zig

@@ -186,6 +186,10 @@ pub fn copyBufferToImage(
     self.proxy.copyBufferToImage(src_buffer, dst_image, dst_image_layout, regions);
 }
 
+pub fn nextSubpass(self: CommandBuffer, contents: vk.SubpassContents) void {
+    self.proxy.nextSubpass(contents);
+}
+
 pub fn pipelineBarrier(self: CommandBuffer, barrier: PipelineBarrier) void {
     self.proxy.pipelineBarrier(
         barrier.src_stage_mask,

src/engine/Skybox.zig

@@ -771,24 +771,7 @@ pub fn deinit(self: *Skybox, engine: *Engine) void {
     engine.destroyImage(self.image);
 }
 
-pub fn bind(self: *const Skybox, command_buffer: CommandBuffer, extent: vk.Extent2D) !void {
-    command_buffer.setViewport(0, &.{
-        .{
-            .x = 0,
-            .y = 0,
-            .width = @floatFromInt(extent.width),
-            .height = @floatFromInt(extent.height),
-            .min_depth = 0,
-            .max_depth = 1,
-        },
-    });
-    command_buffer.setScissor(0, &.{
-        .{
-            .offset = .{ .x = 0, .y = 0 },
-            .extent = extent,
-        },
-    });
-    command_buffer.bindPipeline(.graphics, self.pipeline);
+pub fn draw(self: *const Skybox, command_buffer: CommandBuffer) !void {
     try command_buffer.bindVertexBuffers(0, &.{
         .{
             .buffer = self.vertex_buffer.buffer,
@@ -796,9 +779,8 @@ pub fn bind(self: *const Skybox, command_buffer: CommandBuffer, extent: vk.Exten
         },
     });
     command_buffer.bindIndexBuffer(self.index_buffer.buffer, 0, .uint16);
-}
 
-pub fn draw(self: *const Skybox, command_buffer: CommandBuffer) void {
+    command_buffer.bindPipeline(.graphics, self.pipeline);
     command_buffer.bindDescriptorSet(.graphics, self.pipeline_layout, 0, self.descriptor_set, null);
     command_buffer.drawIndexed(.{ .index_count = 36 });
 }

src/engine/Swapchain.zig

@@ -52,6 +52,7 @@ pub fn init(engine: *Engine) !Swapchain {
             },
         },
         .subpasses = &.{
+            // Main
             .{
                 .pipeline_bind_point = .graphics,
                 .color_attachments = &.{
@@ -65,6 +66,16 @@ pub fn init(engine: *Engine) !Swapchain {
                     .layout = .depth_stencil_attachment_optimal,
                 },
             },
+            // GUI
+            .{
+                .pipeline_bind_point = .graphics,
+                .color_attachments = &.{
+                    .{
+                        .attachment = 0,
+                        .layout = .color_attachment_optimal,
+                    },
+                },
+            },
         },
         .dependencies = &.{
             .{
@@ -89,6 +100,25 @@ pub fn init(engine: *Engine) !Swapchain {
                     .by_region_bit = true,
                 },
             },
+            .{
+                .src_subpass = 0,
+                .dst_subpass = 1,
+                .src_stage_mask = .{
+                    .color_attachment_output_bit = true,
+                },
+                .dst_stage_mask = .{
+                    .color_attachment_output_bit = true,
+                },
+                .src_access_mask = .{
+                    .color_attachment_write_bit = true,
+                },
+                .dst_access_mask = .{
+                    .color_attachment_write_bit = true,
+                },
+                .dependency_flags = .{
+                    .by_region_bit = true,
+                },
+            },
         },
     });
     errdefer engine.destroyRenderPass(render_pass);
@@ -129,6 +159,8 @@ pub fn deinit(self: *Swapchain, engine: *Engine) void {
 }
 
 pub fn recreate(self: *Swapchain, engine: *Engine) !void {
+    try engine.deviceWaitIdle(); // TODO LMAO
+
     const mode = &engine.mode.surface;
     const allocator = engine.vk_allocator.allocator;
 

src/engine/VkAllocator.zig

@@ -132,7 +132,7 @@ fn freeFunction(
     const self: *VkAllocator = @ptrCast(@alignCast(p_user_data.?));
 
     if (maybe_p_memory) |p_memory| {
-        self.mutex.lockUncancelable();
+        self.mutex.lockUncancelable(self.io);
         defer self.mutex.unlock(self.io);
 
         const size = self.allocations.fetchRemove(p_memory).?.value;

src/shaders.zig

@@ -46,6 +46,7 @@ pub const Index = u16;
 pub const GlobalUniforms = extern struct {
     matrixWStoVS: vm.Matrix4x4,
     matrixVStoCS: vm.Matrix4x4,
+    matrixSSPXtoCS: vm.Matrix3x2,
     ambientLight: vm.Vector3,
 };
 
@@ -96,6 +97,8 @@ pub const ObjectUniforms = extern struct {
 };
 
 pub const equirect_to_cube_comp_spv align(4) = @embedFile("shaders/equirect_to_cube_comp.spv").*;
+pub const gui_box_vert_spv align(4) = @embedFile("shaders/gui_box_vert.spv").*;
+pub const gui_box_frag_spv align(4) = @embedFile("shaders/gui_box_frag.spv").*;
 pub const main_vert_spv align(4) = @embedFile("shaders/main_vert.spv").*;
 pub const main_frag_spv align(4) = @embedFile("shaders/main_frag.spv").*;
 pub const skybox_vert_spv align(4) = @embedFile("shaders/skybox_vert.spv").*;