cell-model/obj.c

#include "cell.h"
#include <string.h>
#include <stdlib.h>

#define TINYOBJ_LOADER_C_IMPLEMENTATION
#include "tinyobj_loader_c.h"

typedef struct {
  const char *data;
  size_t len;
} obj_reader_ctx_t;

static void obj_file_reader(void *ctx, const char *filename, int is_mtl, const char *obj_filename, char **buf, size_t *len)
{
  (void)filename;
  (void)obj_filename;

  if (buf) *buf = NULL;
  if (len) *len = 0;
  if (is_mtl) return;

  if (!ctx || !buf || !len) return;

  obj_reader_ctx_t *rctx = (obj_reader_ctx_t *)ctx;
  *buf = (char *)rctx->data;
  *len = rctx->len;
}

static JSValue make_float_array(JSContext *js, const float *arr, int count)
{
  JSValue a = JS_NewArray(js);
  for (int i = 0; i < count; i++)
    JS_SetPropertyUint32(js, a, i, JS_NewFloat64(js, arr[i]));
  return a;
}

JSValue js_obj_decode(JSContext *js, JSValue this_val, int argc, JSValueConst *argv)
{
  size_t len;
  void *raw = js_get_blob_data(js, &len, argv[0]);
  if (raw == NULL) return JS_EXCEPTION;

  tinyobj_attrib_t attrib;
  tinyobj_shape_t *shapes = NULL;
  tinyobj_material_t *materials = NULL;
  size_t num_shapes, num_materials;

  obj_reader_ctx_t rctx;
  rctx.data = (const char *)raw;
  rctx.len = len;

  int result = tinyobj_parse_obj(&attrib, &shapes, &num_shapes, &materials, &num_materials,
                                  "blob.obj", obj_file_reader, &rctx, TINYOBJ_FLAG_TRIANGULATE);

  if (result != TINYOBJ_SUCCESS)
    return JS_ThrowReferenceError(js, "failed to parse OBJ file");

  JSValue obj = JS_NewObject(js);

  // Build unified buffer with all vertex data for all shapes
  // First pass: count total vertices across all shapes
  size_t total_vertices = 0;
  int global_has_normals = 0;
  int global_has_uvs = 0;

  for (size_t si = 0; si < num_shapes; si++) {
    tinyobj_shape_t *shape = &shapes[si];
    total_vertices += shape->length * 3;

    // Check if any shape has normals/uvs
    for (size_t fi = 0; fi < shape->length; fi++) {
      size_t face_idx = shape->face_offset + fi;
      for (int vi = 0; vi < 3; vi++) {
        tinyobj_vertex_index_t idx = attrib.faces[face_idx * 3 + vi];
        if (idx.vn_idx >= 0) global_has_normals = 1;
        if (idx.vt_idx >= 0) global_has_uvs = 1;
      }
    }
  }

  // Calculate buffer layout
  size_t pos_size = total_vertices * 3 * sizeof(float);
  size_t norm_size = global_has_normals ? total_vertices * 3 * sizeof(float) : 0;
  size_t uv_size = global_has_uvs ? total_vertices * 2 * sizeof(float) : 0;
  size_t idx_size = total_vertices * (total_vertices > 65535 ? sizeof(uint32_t) : sizeof(uint16_t));
  int use_32bit = (total_vertices > 65535);

  size_t total_buffer_size = pos_size + norm_size + uv_size + idx_size;

  // Allocate and fill buffer
  uint8_t *buffer_data = malloc(total_buffer_size);
  float *positions = (float *)buffer_data;
  float *normals = global_has_normals ? (float *)(buffer_data + pos_size) : NULL;
  float *uvs = global_has_uvs ? (float *)(buffer_data + pos_size + norm_size) : NULL;
  void *indices = buffer_data + pos_size + norm_size + uv_size;

  size_t vertex_offset = 0;
  for (size_t si = 0; si < num_shapes; si++) {
    tinyobj_shape_t *shape = &shapes[si];
    size_t num_faces = shape->length;

    for (size_t fi = 0; fi < num_faces; fi++) {
      size_t face_idx = shape->face_offset + fi;

      for (int vi = 0; vi < 3; vi++) {
        tinyobj_vertex_index_t idx = attrib.faces[face_idx * 3 + vi];
        size_t v = vertex_offset;

        // Position
        int v_idx = idx.v_idx;
        if (v_idx >= 0 && v_idx < (int)(attrib.num_vertices)) {
          positions[v * 3 + 0] = attrib.vertices[v_idx * 3 + 0];
          positions[v * 3 + 1] = attrib.vertices[v_idx * 3 + 1];
          positions[v * 3 + 2] = attrib.vertices[v_idx * 3 + 2];
        } else {
          positions[v * 3 + 0] = 0;
          positions[v * 3 + 1] = 0;
          positions[v * 3 + 2] = 0;
        }

        // Normal
        if (normals) {
          int vn_idx = idx.vn_idx;
          if (vn_idx >= 0 && vn_idx < (int)(attrib.num_normals)) {
            normals[v * 3 + 0] = attrib.normals[vn_idx * 3 + 0];
            normals[v * 3 + 1] = attrib.normals[vn_idx * 3 + 1];
            normals[v * 3 + 2] = attrib.normals[vn_idx * 3 + 2];
          } else {
            normals[v * 3 + 0] = 0;
            normals[v * 3 + 1] = 1;
            normals[v * 3 + 2] = 0;
          }
        }

        // UV
        if (uvs) {
          int vt_idx = idx.vt_idx;
          if (vt_idx >= 0 && vt_idx < (int)(attrib.num_texcoords)) {
            uvs[v * 2 + 0] = attrib.texcoords[vt_idx * 2 + 0];
            uvs[v * 2 + 1] = attrib.texcoords[vt_idx * 2 + 1];
          } else {
            uvs[v * 2 + 0] = 0;
            uvs[v * 2 + 1] = 0;
          }
        }

        // Index
        if (use_32bit)
          ((uint32_t *)indices)[v] = (uint32_t)v;
        else
          ((uint16_t *)indices)[v] = (uint16_t)v;

        vertex_offset++;
      }
    }
  }

  // Create buffer
  JSValue buffers_arr = JS_NewArray(js);
  JSValue buf = JS_NewObject(js);
  JS_SetPropertyStr(js, buf, "blob", js_new_blob_stoned_copy(js, buffer_data, total_buffer_size));
  JS_SetPropertyStr(js, buf, "byte_length", JS_NewInt64(js, total_buffer_size));
  JS_SetPropertyUint32(js, buffers_arr, 0, buf);
  JS_SetPropertyStr(js, obj, "buffers", buffers_arr);

  // Create views
  JSValue views_arr = JS_NewArray(js);
  int view_idx = 0;

  // Position view
  JSValue pos_view = JS_NewObject(js);
  JS_SetPropertyStr(js, pos_view, "buffer", JS_NewInt32(js, 0));
  JS_SetPropertyStr(js, pos_view, "byte_offset", JS_NewInt64(js, 0));
  JS_SetPropertyStr(js, pos_view, "byte_length", JS_NewInt64(js, pos_size));
  JS_SetPropertyStr(js, pos_view, "byte_stride", JS_NULL);
  JS_SetPropertyStr(js, pos_view, "usage", JS_NewString(js, "vertex"));
  JS_SetPropertyUint32(js, views_arr, view_idx++, pos_view);
  int pos_view_idx = 0;

  int norm_view_idx = -1;
  if (global_has_normals) {
    JSValue norm_view = JS_NewObject(js);
    JS_SetPropertyStr(js, norm_view, "buffer", JS_NewInt32(js, 0));
    JS_SetPropertyStr(js, norm_view, "byte_offset", JS_NewInt64(js, pos_size));
    JS_SetPropertyStr(js, norm_view, "byte_length", JS_NewInt64(js, norm_size));
    JS_SetPropertyStr(js, norm_view, "byte_stride", JS_NULL);
    JS_SetPropertyStr(js, norm_view, "usage", JS_NewString(js, "vertex"));
    norm_view_idx = view_idx;
    JS_SetPropertyUint32(js, views_arr, view_idx++, norm_view);
  }

  int uv_view_idx = -1;
  if (global_has_uvs) {
    JSValue uv_view = JS_NewObject(js);
    JS_SetPropertyStr(js, uv_view, "buffer", JS_NewInt32(js, 0));
    JS_SetPropertyStr(js, uv_view, "byte_offset", JS_NewInt64(js, pos_size + norm_size));
    JS_SetPropertyStr(js, uv_view, "byte_length", JS_NewInt64(js, uv_size));
    JS_SetPropertyStr(js, uv_view, "byte_stride", JS_NULL);
    JS_SetPropertyStr(js, uv_view, "usage", JS_NewString(js, "vertex"));
    uv_view_idx = view_idx;
    JS_SetPropertyUint32(js, views_arr, view_idx++, uv_view);
  }

  // Index view
  JSValue idx_view = JS_NewObject(js);
  JS_SetPropertyStr(js, idx_view, "buffer", JS_NewInt32(js, 0));
  JS_SetPropertyStr(js, idx_view, "byte_offset", JS_NewInt64(js, pos_size + norm_size + uv_size));
  JS_SetPropertyStr(js, idx_view, "byte_length", JS_NewInt64(js, idx_size));
  JS_SetPropertyStr(js, idx_view, "byte_stride", JS_NULL);
  JS_SetPropertyStr(js, idx_view, "usage", JS_NewString(js, "index"));
  int idx_view_idx = view_idx;
  JS_SetPropertyUint32(js, views_arr, view_idx++, idx_view);

  JS_SetPropertyStr(js, obj, "views", views_arr);

  // Create accessors
  JSValue accessors_arr = JS_NewArray(js);
  int acc_idx = 0;

  // Position accessor
  JSValue pos_acc = JS_NewObject(js);
  JS_SetPropertyStr(js, pos_acc, "view", JS_NewInt32(js, pos_view_idx));
  JS_SetPropertyStr(js, pos_acc, "byte_offset", JS_NewInt64(js, 0));
  JS_SetPropertyStr(js, pos_acc, "count", JS_NewInt64(js, total_vertices));
  JS_SetPropertyStr(js, pos_acc, "component_type", JS_NewString(js, "f32"));
  JS_SetPropertyStr(js, pos_acc, "type", JS_NewString(js, "vec3"));
  JS_SetPropertyStr(js, pos_acc, "normalized", JS_FALSE);
  JS_SetPropertyStr(js, pos_acc, "min", JS_NULL);
  JS_SetPropertyStr(js, pos_acc, "max", JS_NULL);
  int pos_acc_idx = acc_idx;
  JS_SetPropertyUint32(js, accessors_arr, acc_idx++, pos_acc);

  int norm_acc_idx = -1;
  if (global_has_normals) {
    JSValue norm_acc = JS_NewObject(js);
    JS_SetPropertyStr(js, norm_acc, "view", JS_NewInt32(js, norm_view_idx));
    JS_SetPropertyStr(js, norm_acc, "byte_offset", JS_NewInt64(js, 0));
    JS_SetPropertyStr(js, norm_acc, "count", JS_NewInt64(js, total_vertices));
    JS_SetPropertyStr(js, norm_acc, "component_type", JS_NewString(js, "f32"));
    JS_SetPropertyStr(js, norm_acc, "type", JS_NewString(js, "vec3"));
    JS_SetPropertyStr(js, norm_acc, "normalized", JS_FALSE);
    JS_SetPropertyStr(js, norm_acc, "min", JS_NULL);
    JS_SetPropertyStr(js, norm_acc, "max", JS_NULL);
    norm_acc_idx = acc_idx;
    JS_SetPropertyUint32(js, accessors_arr, acc_idx++, norm_acc);
  }

  int uv_acc_idx = -1;
  if (global_has_uvs) {
    JSValue uv_acc = JS_NewObject(js);
    JS_SetPropertyStr(js, uv_acc, "view", JS_NewInt32(js, uv_view_idx));
    JS_SetPropertyStr(js, uv_acc, "byte_offset", JS_NewInt64(js, 0));
    JS_SetPropertyStr(js, uv_acc, "count", JS_NewInt64(js, total_vertices));
    JS_SetPropertyStr(js, uv_acc, "component_type", JS_NewString(js, "f32"));
    JS_SetPropertyStr(js, uv_acc, "type", JS_NewString(js, "vec2"));
    JS_SetPropertyStr(js, uv_acc, "normalized", JS_FALSE);
    JS_SetPropertyStr(js, uv_acc, "min", JS_NULL);
    JS_SetPropertyStr(js, uv_acc, "max", JS_NULL);
    uv_acc_idx = acc_idx;
    JS_SetPropertyUint32(js, accessors_arr, acc_idx++, uv_acc);
  }

  // Index accessor
  JSValue idx_acc = JS_NewObject(js);
  JS_SetPropertyStr(js, idx_acc, "view", JS_NewInt32(js, idx_view_idx));
  JS_SetPropertyStr(js, idx_acc, "byte_offset", JS_NewInt64(js, 0));
  JS_SetPropertyStr(js, idx_acc, "count", JS_NewInt64(js, total_vertices));
  JS_SetPropertyStr(js, idx_acc, "component_type", JS_NewString(js, use_32bit ? "u32" : "u16"));
  JS_SetPropertyStr(js, idx_acc, "type", JS_NewString(js, "scalar"));
  JS_SetPropertyStr(js, idx_acc, "normalized", JS_FALSE);
  JS_SetPropertyStr(js, idx_acc, "min", JS_NULL);
  JS_SetPropertyStr(js, idx_acc, "max", JS_NULL);
  int idx_acc_idx = acc_idx;
  JS_SetPropertyUint32(js, accessors_arr, acc_idx++, idx_acc);

  JS_SetPropertyStr(js, obj, "accessors", accessors_arr);

  // Create meshes - each shape becomes a mesh with one primitive
  // But we need per-shape accessors since they reference different ranges
  // Actually, for OBJ we'll create per-shape accessors that point to subranges

  // Rebuild accessors per shape
  JS_FreeValue(js, accessors_arr);
  accessors_arr = JS_NewArray(js);
  acc_idx = 0;

  JSValue meshes_arr = JS_NewArray(js);
  vertex_offset = 0;

  for (size_t si = 0; si < num_shapes; si++) {
    tinyobj_shape_t *shape = &shapes[si];
    size_t shape_vertices = shape->length * 3;

    // Create accessors for this shape
    int shape_pos_acc = acc_idx;
    JSValue spa = JS_NewObject(js);
    JS_SetPropertyStr(js, spa, "view", JS_NewInt32(js, pos_view_idx));
    JS_SetPropertyStr(js, spa, "byte_offset", JS_NewInt64(js, vertex_offset * 3 * sizeof(float)));
    JS_SetPropertyStr(js, spa, "count", JS_NewInt64(js, shape_vertices));
    JS_SetPropertyStr(js, spa, "component_type", JS_NewString(js, "f32"));
    JS_SetPropertyStr(js, spa, "type", JS_NewString(js, "vec3"));
    JS_SetPropertyStr(js, spa, "normalized", JS_FALSE);
    JS_SetPropertyStr(js, spa, "min", JS_NULL);
    JS_SetPropertyStr(js, spa, "max", JS_NULL);
    JS_SetPropertyUint32(js, accessors_arr, acc_idx++, spa);

    int shape_norm_acc = -1;
    if (global_has_normals) {
      shape_norm_acc = acc_idx;
      JSValue sna = JS_NewObject(js);
      JS_SetPropertyStr(js, sna, "view", JS_NewInt32(js, norm_view_idx));
      JS_SetPropertyStr(js, sna, "byte_offset", JS_NewInt64(js, vertex_offset * 3 * sizeof(float)));
      JS_SetPropertyStr(js, sna, "count", JS_NewInt64(js, shape_vertices));
      JS_SetPropertyStr(js, sna, "component_type", JS_NewString(js, "f32"));
      JS_SetPropertyStr(js, sna, "type", JS_NewString(js, "vec3"));
      JS_SetPropertyStr(js, sna, "normalized", JS_FALSE);
      JS_SetPropertyStr(js, sna, "min", JS_NULL);
      JS_SetPropertyStr(js, sna, "max", JS_NULL);
      JS_SetPropertyUint32(js, accessors_arr, acc_idx++, sna);
    }

    int shape_uv_acc = -1;
    if (global_has_uvs) {
      shape_uv_acc = acc_idx;
      JSValue sua = JS_NewObject(js);
      JS_SetPropertyStr(js, sua, "view", JS_NewInt32(js, uv_view_idx));
      JS_SetPropertyStr(js, sua, "byte_offset", JS_NewInt64(js, vertex_offset * 2 * sizeof(float)));
      JS_SetPropertyStr(js, sua, "count", JS_NewInt64(js, shape_vertices));
      JS_SetPropertyStr(js, sua, "component_type", JS_NewString(js, "f32"));
      JS_SetPropertyStr(js, sua, "type", JS_NewString(js, "vec2"));
      JS_SetPropertyStr(js, sua, "normalized", JS_FALSE);
      JS_SetPropertyStr(js, sua, "min", JS_NULL);
      JS_SetPropertyStr(js, sua, "max", JS_NULL);
      JS_SetPropertyUint32(js, accessors_arr, acc_idx++, sua);
    }

    int shape_idx_acc = acc_idx;
    JSValue sia = JS_NewObject(js);
    JS_SetPropertyStr(js, sia, "view", JS_NewInt32(js, idx_view_idx));
    JS_SetPropertyStr(js, sia, "byte_offset", JS_NewInt64(js, vertex_offset * (use_32bit ? sizeof(uint32_t) : sizeof(uint16_t))));
    JS_SetPropertyStr(js, sia, "count", JS_NewInt64(js, shape_vertices));
    JS_SetPropertyStr(js, sia, "component_type", JS_NewString(js, use_32bit ? "u32" : "u16"));
    JS_SetPropertyStr(js, sia, "type", JS_NewString(js, "scalar"));
    JS_SetPropertyStr(js, sia, "normalized", JS_FALSE);
    JS_SetPropertyStr(js, sia, "min", JS_NULL);
    JS_SetPropertyStr(js, sia, "max", JS_NULL);
    JS_SetPropertyUint32(js, accessors_arr, acc_idx++, sia);

    // Create mesh
    JSValue mesh = JS_NewObject(js);
    JS_SetPropertyStr(js, mesh, "name", shape->name ? JS_NewString(js, shape->name) : JS_NULL);

    JSValue prims_arr = JS_NewArray(js);
    JSValue prim = JS_NewObject(js);
    JS_SetPropertyStr(js, prim, "topology", JS_NewString(js, "triangles"));

    JSValue attrs = JS_NewObject(js);
    JS_SetPropertyStr(js, attrs, "POSITION", JS_NewInt32(js, shape_pos_acc));
    if (shape_norm_acc >= 0)
      JS_SetPropertyStr(js, attrs, "NORMAL", JS_NewInt32(js, shape_norm_acc));
    if (shape_uv_acc >= 0)
      JS_SetPropertyStr(js, attrs, "TEXCOORD_0", JS_NewInt32(js, shape_uv_acc));
    JS_SetPropertyStr(js, prim, "attributes", attrs);

    JS_SetPropertyStr(js, prim, "indices", JS_NewInt32(js, shape_idx_acc));
    JS_SetPropertyStr(js, prim, "material", JS_NULL);

    JS_SetPropertyUint32(js, prims_arr, 0, prim);
    JS_SetPropertyStr(js, mesh, "primitives", prims_arr);

    JS_SetPropertyUint32(js, meshes_arr, si, mesh);
    vertex_offset += shape_vertices;
  }

  JS_SetPropertyStr(js, obj, "accessors", accessors_arr);
  JS_SetPropertyStr(js, obj, "meshes", meshes_arr);

  // Materials from OBJ
  JSValue materials_arr = JS_NewArray(js);
  for (size_t i = 0; i < num_materials; i++) {
    tinyobj_material_t *mat = &materials[i];
    JSValue m = JS_NewObject(js);
    JS_SetPropertyStr(js, m, "name", mat->name ? JS_NewString(js, mat->name) : JS_NULL);

    JSValue pbr = JS_NewObject(js);
    float bc[4] = {mat->diffuse[0], mat->diffuse[1], mat->diffuse[2], 1.0f};
    JS_SetPropertyStr(js, pbr, "base_color_factor", make_float_array(js, bc, 4));
    JS_SetPropertyStr(js, pbr, "base_color_texture", JS_NULL);
    JS_SetPropertyStr(js, pbr, "metallic_factor", JS_NewFloat64(js, 0.0));
    JS_SetPropertyStr(js, pbr, "roughness_factor", JS_NewFloat64(js, 1.0));
    JS_SetPropertyStr(js, pbr, "metallic_roughness_texture", JS_NULL);
    JS_SetPropertyStr(js, pbr, "normal_texture", JS_NULL);
    JS_SetPropertyStr(js, pbr, "occlusion_texture", JS_NULL);
    float ef[3] = {mat->emission[0], mat->emission[1], mat->emission[2]};
    JS_SetPropertyStr(js, pbr, "emissive_factor", make_float_array(js, ef, 3));
    JS_SetPropertyStr(js, pbr, "emissive_texture", JS_NULL);
    JS_SetPropertyStr(js, m, "pbr", pbr);

    JS_SetPropertyStr(js, m, "alpha_mode", JS_NewString(js, "OPAQUE"));
    JS_SetPropertyStr(js, m, "alpha_cutoff", JS_NewFloat64(js, 0.5));
    JS_SetPropertyStr(js, m, "double_sided", JS_FALSE);

    JS_SetPropertyUint32(js, materials_arr, i, m);
  }
  JS_SetPropertyStr(js, obj, "materials", materials_arr);

  // Empty arrays for unsupported features
  JS_SetPropertyStr(js, obj, "images", JS_NewArray(js));
  JS_SetPropertyStr(js, obj, "textures", JS_NewArray(js));
  JS_SetPropertyStr(js, obj, "samplers", JS_NewArray(js));

  // Nodes - one node per mesh
  JSValue nodes_arr = JS_NewArray(js);
  JSValue scene_nodes = JS_NewArray(js);
  for (size_t i = 0; i < num_shapes; i++) {
    JSValue n = JS_NewObject(js);
    JS_SetPropertyStr(js, n, "name", shapes[i].name ? JS_NewString(js, shapes[i].name) : JS_NULL);
    JS_SetPropertyStr(js, n, "mesh", JS_NewInt32(js, i));
    JS_SetPropertyStr(js, n, "children", JS_NewArray(js));
    JS_SetPropertyStr(js, n, "matrix", JS_NULL);
    float t[3] = {0, 0, 0};
    float r[4] = {0, 0, 0, 1};
    float s[3] = {1, 1, 1};
    JS_SetPropertyStr(js, n, "translation", make_float_array(js, t, 3));
    JS_SetPropertyStr(js, n, "rotation", make_float_array(js, r, 4));
    JS_SetPropertyStr(js, n, "scale", make_float_array(js, s, 3));
    JS_SetPropertyStr(js, n, "skin", JS_NULL);
    JS_SetPropertyUint32(js, nodes_arr, i, n);
    JS_SetPropertyUint32(js, scene_nodes, i, JS_NewInt32(js, i));
  }
  JS_SetPropertyStr(js, obj, "nodes", nodes_arr);

  // Scenes
  JSValue scenes_arr = JS_NewArray(js);
  JSValue scene = JS_NewObject(js);
  JS_SetPropertyStr(js, scene, "nodes", scene_nodes);
  JS_SetPropertyUint32(js, scenes_arr, 0, scene);
  JS_SetPropertyStr(js, obj, "scenes", scenes_arr);
  JS_SetPropertyStr(js, obj, "scene", JS_NewInt32(js, 0));

  // Empty arrays for animations/skins
  JS_SetPropertyStr(js, obj, "animations", JS_NewArray(js));
  JS_SetPropertyStr(js, obj, "skins", JS_NewArray(js));

  // Extensions
  JSValue exts = JS_NewObject(js);
  JS_SetPropertyStr(js, exts, "used", JS_NewArray(js));
  JS_SetPropertyStr(js, exts, "required", JS_NewArray(js));
  JS_SetPropertyStr(js, obj, "extensions", exts);

  free(buffer_data);
  tinyobj_attrib_free(&attrib);
  tinyobj_shapes_free(shapes, num_shapes);
  tinyobj_materials_free(materials, num_materials);

  return obj;
}

static const JSCFunctionListEntry js_obj_funcs[] = {
  MIST_FUNC_DEF(obj, decode, 1),
};

CELL_USE_FUNCS(js_obj_funcs)