multires_reshape_ccg.cc

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/* SPDX-FileCopyrightText: 2020 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#include "multires_reshape.hh"
 
#include <cstring>
 
#include "BLI_utildefines.h"
 
#include "BKE_ccg.hh"
#include "BKE_subdiv_ccg.hh"
 
bool multires_reshape_assign_final_coords_from_ccg(const MultiresReshapeContext *reshape_context,
                                                   SubdivCCG *subdiv_ccg)
{
  using namespace blender;
  const CCGKey reshape_level_key = BKE_subdiv_ccg_key(*subdiv_ccg, reshape_context->reshape.level);
 
  const int reshape_grid_size = reshape_context->reshape.grid_size;
  const float reshape_grid_size_1_inv = 1.0f / (float(reshape_grid_size) - 1.0f);
 
  const Span<float3> positions = subdiv_ccg->positions;
  const Span<float> masks = subdiv_ccg->masks;
 
  int num_grids = subdiv_ccg->grids_num;
  for (int grid_index = 0; grid_index < num_grids; ++grid_index) {
    for (int y = 0; y < reshape_grid_size; ++y) {
      const float v = float(y) * reshape_grid_size_1_inv;
      for (int x = 0; x < reshape_grid_size; ++x) {
        const float u = float(x) * reshape_grid_size_1_inv;
        const int vert = bke::ccg::grid_xy_to_vert(reshape_level_key, grid_index, x, y);
 
        GridCoord grid_coord;
        grid_coord.grid_index = grid_index;
        grid_coord.u = u;
        grid_coord.v = v;
 
        ReshapeGridElement grid_element = multires_reshape_grid_element_for_grid_coord(
            reshape_context, &grid_coord);
 
        BLI_assert(grid_element.displacement != nullptr);
        memcpy(grid_element.displacement, positions[vert], sizeof(float[3]));
 
        /* NOTE: The sculpt mode might have SubdivCCG's data out of sync from what is stored in
         * the original object. This happens in the following scenario:
         *
         *  - User enters sculpt mode of the default cube object.
         *  - Sculpt mode creates new `layer`
         *  - User does some strokes.
         *  - User used undo until sculpt mode is exited.
         *
         * In an ideal world the sculpt mode will take care of keeping CustomData and CCG layers in
         * sync by doing proper pushes to a local sculpt undo stack.
         *
         * Since the proper solution needs time to be implemented, consider the target object
         * the source of truth of which data layers are to be updated during reshape. This means,
         * for example, that if the undo system says object does not have paint mask layer, it is
         * not to be updated.
         *
         * This is fragile logic, and is only working correctly because the code path is only
         * used by sculpt changes. In other use cases the code might not catch inconsistency and
         * silently make the wrong decision. */
        /* NOTE: There is a known bug in Undo code that results in first Sculpt step
         * after a Memfile one to never be undone (see #83806). This might be the root cause of
         * this inconsistency. */
        if (!subdiv_ccg->masks.is_empty() && grid_element.mask != nullptr) {
          *grid_element.mask = masks[vert];
        }
      }
    }
  }
 
  return true;
}