implemented glTF loading

1 files changed, 155 insertions, 5 deletions

diff --git a/src/rendering/gltf.zig b/src/rendering/gltf.zig
index 614ee25..888191d 100644
--- a/src/rendering/gltf.zig
+++ b/src/rendering/gltf.zig
@@ -2,15 +2,165 @@ const std = @import("std");
 const mesh = @import("mesh.zig");
 const Allocator = std.mem.Allocator;
 
-pub const Model = packed struct {
+pub const Model = struct {
+    const Asset = struct {
+        version: []u8,
+        generator: ?[]u8 = null,
+        copyright: ?[]u8 = null,
+    };
+    const Buffer = struct {
+        byteLength: usize,
+        uri: ?[]u8 = null,
+    };
+    const BufferView = struct {
+        buffer: usize,
+        byteLength: usize,
+        byteOffset: usize,
+        byteStride: ?usize = null,
+        target: ?usize = null,
+    };
+    const Node = struct {
+        name: []u8,
+        mesh: ?usize = null,
+        weights: ?[]f64 = null,
+        children: ?[]usize = null,
+        rotation: ?[4]f64 = null,
+        scale: ?[3]f64 = null,
+        translation: ?[3]f64 = null,
+        camera: ?usize = null,
+        matrix: ?[16]usize = null,
+    };
+    const Accessor = struct {
+        bufferView: usize,
+        byteOffset: ?usize = null,
+        componentType: usize,
+        count: usize,
+        type: []u8,
+        max: ?[]f64 = null,
+        min: ?[]f64 = null,
+    };
+    const Primitive = struct {
+        const Attributes = struct {
+            NORMAL: ?usize = null,
+            POSITION: ?usize = null,
+            TANGENT: ?usize = null,
+            TEXCOORD_0: ?usize = null,
+            TEXCOORD_1: ?usize = null,
+            COLOR_0: ?usize = null,
+            JOINTS_0: ?usize = null,
+            WEIGHTS_0: ?usize = null,
+        };
+
+        attributes: ?Attributes = null,
+        indices: ?usize = null,
+        material: ?usize = null,
+        mode: ?usize = null,
+    };
+    const Mesh = struct {
+        name: ?[]u8 = null,
+        primitives: ?[]Primitive = null,
+        weights: ?[]f64 = null,
+    };
+    const Skin = struct {
+        inverseBindMatrices: usize,
+        joints: []usize,
+        skeleton: usize,
+    };
+    const Texture = struct {
+        sampler: usize,
+        source: usize,
+    };
+    const Image = struct {
+        uri: ?[]u8 = null,
+        bufferView: ?usize = null,
+        mimeType: ?[]u8 = null,
+    };
+    const Material = struct {
+        const Pbr = struct {
+            baseColorFactor: ?[4]f64 = null,
+            baseColorTexture: ?struct {
+                index: usize,
+                texCoord: usize,
+            } = null,
+            metallicFactor: ?f64 = null,
+            roughnessFactor: ?f64 = null,
+        };
+        name: ?[]u8 = null,
+        pbrMetallicRoughness: Pbr,
+        doubleSided: bool,
+    };
+    const Scene = struct {
+        nodes: ?[]usize = null,
+        name: ?[]u8 = null,
+    };
+
     const Chunk = packed struct {
+        const offset = Header.offset + 8;
         length: u32,
-        ty: u32,
+        type: u32,
+    };
 
-    },
-    header: packed struct {
+    const JsonChunk = struct {
+        asset: Asset,
+        scene: usize,
+        scenes: ?[]Scene = null,
+        nodes: ?[]Node = null,
+        materials: ?[]Material = null,
+        meshes: ?[]Mesh = null,
+        accessors: ?[]Accessor = null,
+        bufferViews: ?[]BufferView = null,
+        buffers: ?[]Buffer = null,
+    };
+
+    const Header = packed struct {
+        const offset = 12;
         magic: u32,
         version: u32,
         length: u32,
-    },
+    };
+
+    const Binary = struct {
+        data: []u8,
+        const Vec3 = [3]f32;
+
+        pub fn readU16(self: Binary, allocator: Allocator, view: BufferView, count: usize) ![]u16 {
+            const data = self.data[view.byteOffset .. view.byteOffset + view.byteLength];
+            const scalars = try allocator.alloc(u16, count);
+
+            var j: usize = 0;
+            for (0..data.len / 2) |i| {
+                scalars[i] = std.mem.bytesAsValue(u16, data[j .. j + 1]).*;
+                j += 2;
+            }
+
+            return scalars;
+        }
+
+        pub fn readVec3(self: Binary, allocator: Allocator, view: BufferView, count: usize) ![]Vec3 {
+            const data = self.data[view.byteOffset .. view.byteOffset + view.byteLength];
+            const vectors = try allocator.alloc(Vec3, count);
+
+            for (0..count) |i| {
+                vectors[i] = std.mem.bytesAsValue(Vec3, data[(@sizeOf(Vec3) * i) .. (@sizeOf(Vec3) * i) + @sizeOf(Vec3)]).*;
+            }
+
+            return vectors;
+        }
+    };
 };
+
+pub fn parseFile(allocator: Allocator, name: []const u8) !struct { vertices: [][3]f32, indices: []u16 } {
+    const file = try std.fs.cwd().openFile(name, .{});
+    const all = try file.readToEndAlloc(allocator, 1_000_000);
+    const json_chunk = std.mem.bytesAsValue(Model.Chunk, all[Model.Header.offset..]);
+
+    const data = (try std.json.parseFromSlice(Model.JsonChunk, allocator, @constCast(all[Model.Chunk.offset .. Model.Chunk.offset + json_chunk.length]), .{ .ignore_unknown_fields = true })).value;
+    const binary = Model.Binary{ .data = all[Model.Chunk.offset + json_chunk.length + 8 ..] };
+
+    const vertices = try binary.readVec3(allocator, data.bufferViews.?[data.meshes.?[0].primitives.?[0].attributes.?.POSITION.?], 24);
+    const indices = try binary.readU16(allocator, data.bufferViews.?[data.meshes.?[0].primitives.?[0].indices.?], 36);
+    std.debug.print("vertices: {any}\n", .{vertices});
+    std.debug.print("indices: {any}\n", .{indices});
+
+    return .{ .vertices = vertices, .indices = indices };
+}