usd_reader_xform.cc

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/* SPDX-FileCopyrightText: 2021 Tangent Animation. All rights reserved.
 * SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Adapted from the Blender Alembic importer implementation. */
 
#include "usd_reader_xform.hh"
 
#include "BKE_constraint.h"
#include "BKE_lib_id.hh"
#include "BKE_object.hh"
 
#include "BLI_math_matrix.h"
#include "BLI_string.h"
 
#include "DNA_cachefile_types.h"
#include "DNA_constraint_types.h"
#include "DNA_object_types.h"
 
#include <pxr/base/gf/matrix4f.h>
#include <pxr/usd/usdGeom/xformable.h>
 
#include <string>
 
namespace blender::io::usd {
 
void USDXformReader::create_object(Main *bmain, const double /*motionSampleTime*/)
{
  object_ = BKE_object_add_only_object(bmain, OB_EMPTY, name_.c_str());
  object_->empty_drawsize = 0.1f;
  object_->data = nullptr;
}
 
void USDXformReader::read_object_data(Main * /*bmain*/, const double motionSampleTime)
{
  bool is_constant;
  float transform_from_usd[4][4];
 
  read_matrix(transform_from_usd, motionSampleTime, import_params_.scale, &is_constant);
 
  if (!is_constant && settings_->get_cache_file) {
    bConstraint *con = BKE_constraint_add_for_object(
        object_, nullptr, CONSTRAINT_TYPE_TRANSFORM_CACHE);
    bTransformCacheConstraint *data = static_cast<bTransformCacheConstraint *>(con->data);
 
    std::string prim_path = use_parent_xform_ ? prim_.GetParent().GetPath().GetAsString() :
                                                prim_path_;
 
    STRNCPY(data->object_path, prim_path.c_str());
 
    data->cache_file = settings_->get_cache_file();
    id_us_plus(&data->cache_file->id);
  }
 
  BKE_object_apply_mat4(object_, transform_from_usd, true, false);
 
  /* Make sure to collect custom attributes */
  set_props(use_parent_xform(), motionSampleTime);
}
 
void USDXformReader::read_matrix(float r_mat[4][4] /* local matrix */,
                                 const float time,
                                 const float scale,
                                 bool *r_is_constant) const
{
  BLI_assert(r_mat);
  BLI_assert(r_is_constant);
 
  *r_is_constant = true;
  unit_m4(r_mat);
 
  std::optional<XformResult> xf_result = get_local_usd_xform(time);
 
  if (!xf_result) {
    return;
  }
 
  std::get<0>(*xf_result).Get(r_mat);
  *r_is_constant = std::get<1>(*xf_result);
 
  /* Apply global scaling and rotation only to root objects, parenting
   * will propagate it. */
  if ((scale != 1.0 || settings_->do_convert_mat) && is_root_xform_) {
 
    if (scale != 1.0f) {
      float scale_mat[4][4];
      scale_m4_fl(scale_mat, scale);
      mul_m4_m4m4(r_mat, scale_mat, r_mat);
    }
 
    if (settings_->do_convert_mat) {
      mul_m4_m4m4(r_mat, settings_->conversion_mat, r_mat);
    }
  }
}
 
bool USDXformReader::prim_has_xform_ops() const
{
  pxr::UsdGeomXformable xformable(prim_);
 
  if (!xformable) {
    /* This might happen if the prim is a Scope. */
    return false;
  }
 
  bool reset_xform_stack = false;
 
  return !xformable.GetOrderedXformOps(&reset_xform_stack).empty();
}
 
bool USDXformReader::is_root_xform_prim() const
{
  if (!prim_.IsValid()) {
    return false;
  }
 
  if (is_in_proto()) {
    /* We don't consider prototypes to be root prims,
     * because we never want to apply global scaling
     * or rotations to the prototypes themselves. */
    return false;
  }
 
  if (prim_.IsA<pxr::UsdGeomXformable>()) {
    /* If this prim doesn't have an ancestor that's a
     * UsdGeomXformable, then it's a root prim.  Note
     * that it's not sufficient to only check the immediate
     * parent prim, since the immediate parent could be a
     * UsdGeomScope that has an xformable ancestor. */
    pxr::UsdPrim cur_parent = prim_.GetParent();
 
    if (use_parent_xform_) {
      cur_parent = cur_parent.GetParent();
    }
 
    while (cur_parent && !cur_parent.IsPseudoRoot()) {
      if (cur_parent.IsA<pxr::UsdGeomXformable>()) {
        return false;
      }
      cur_parent = cur_parent.GetParent();
    }
 
    /* We didn't find an xformable ancestor. */
    return true;
  }
 
  return false;
}
 
std::optional<XformResult> USDXformReader::get_local_usd_xform(const float time) const
{
  pxr::UsdGeomXformable xformable = use_parent_xform_ ? pxr::UsdGeomXformable(prim_.GetParent()) :
                                                        pxr::UsdGeomXformable(prim_);
 
  if (!xformable) {
    /* This might happen if the prim is a Scope. */
    return std::nullopt;
  }
 
  bool is_constant = !xformable.TransformMightBeTimeVarying();
 
  bool reset_xform_stack;
  pxr::GfMatrix4d xform;
  if (!xformable.GetLocalTransformation(&xform, &reset_xform_stack, time)) {
    return std::nullopt;
  }
 
  /* The USD bind transform is a matrix of doubles,
   * but we cast it to GfMatrix4f because Blender expects
   * a matrix of floats. */
  return XformResult(pxr::GfMatrix4f(xform), is_constant);
}
 
}  // namespace blender::io::usd