[Bf-blender-cvs] [d918c2c9072] temp-gpu-texture-partial-updates: WIP: Parial update skeleton.

[Jeroen Bakker]

Commit: d918c2c90720bf994265cd8db6c6ba0acaebce0e
Author: Jeroen Bakker
Date:   Fri Nov 12 15:55:48 2021 +0100
Branches: temp-gpu-texture-partial-updates
https://developer.blender.org/rBd918c2c90720bf994265cd8db6c6ba0acaebce0e

WIP: Parial update skeleton.

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A	source/blender/blenkernel/intern/image_gpu_partial_update.cc

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diff --git a/source/blender/blenkernel/intern/image_gpu_partial_update.cc b/source/blender/blenkernel/intern/image_gpu_partial_update.cc
new file mode 100644
index 00000000000..cfbf01dc21e
--- /dev/null
+++ b/source/blender/blenkernel/intern/image_gpu_partial_update.cc
@@ -0,0 +1,149 @@
+
+/**
+ * \file image_gpu_partial_update.cc
+ *
+ * To reduce the overhead of uploading images to GPU only changed areas will be uploaded.
+ * The areas are organized in tiles.
+ *
+ * Requirements:
+ * - Independent how the actual GPU textures look like. The uploading, transforming are
+ *   responsibility of the user of this API.
+ *
+ *
+ * Usage:
+ *
+ * ```
+ * Image *image = space_data->image;
+ * PartialUpdateUser* partial_update_user = BKE_image_partial_update_create(image);
+ *
+ * if (BKE_image_partial_update_collect_tiles(image, partial_update_user) == DO_FULL_UPDATE {
+ *   // Recreate full GPU texture.
+ *   ...
+ * } else {
+ *   PartialUpdateTile tile;
+ *  int index = 0;
+ *   while(BKE_image_partial_update_get_tile(partial_update_user, index++, &tile) == TILE_VALID) {
+ *     // Do something with the tile.
+ *     ...
+ *   }
+ * }
+ *
+ * BKE_image_partial_update_free(partial_update_user);
+ *
+ * ```
+ */
+
+#include "DNA_image_types.h"
+
+#include "BLI_vector.hh"
+
+namespace blender::bke::image {
+
+/**
+ * \brief A single tile to update.
+ *
+ * Data is organized in tiles. These tiles are in texel space (1 unit is a single texel). When
+ * tiles are requested they are merged with neighboring tiles.
+ */
+struct PartialUpdateTile {
+  /** \brief area of the image that has been updated. */
+  rcti update_area;
+};
+
+using TransactionID = int;
+
+struct PartialUpdateUser {
+ private:
+  TransactionID last_transaction_id;
+
+  /** \brief tiles that have been updated. */
+  Vector<PartialUpdateTile> changed_tiles;
+};
+
+struct PartialUpdateTransaction {
+  /* bitvec for each tile in the transaction. True means that this tile was changed during during
+   * this transaction. */
+  Vector<bool> tile_validity;
+  bool is_empty = true;
+
+  bool is_empty()
+  {
+    return is_empty;
+  }
+};
+
+/** \brief Partial update data that is stored inside the image. */
+struct PartialUpdateImage {
+  TransactionID first_transaction_id;
+  TransactionID current_transaction_id;
+  Vector<PartialUpdateTransaction> history;
+
+  PartialUpdateTransaction current_transaction;
+
+  void invalidate_tile(int tile_x, int tile_y)
+  {
+  }
+
+  void ensure_empty_transaction()
+  {
+    if (current_transaction.is_empty()) {
+      /* No need to create a new transaction when previous transaction does not contain any data.
+       */
+      return;
+    }
+    commit_current_transaction();
+  }
+
+  void commit_current_transaction()
+  {
+    history.append_as(std::move(current_transaction));
+    current_transaction_id++;
+  }
+}
+
+}  // namespace blender::bke::image
+
+extern "C" {
+struct PartialUpdateUser;
+using namespace blender::bke::image;
+
+PartialUpdateUser *BKE_image_partial_update_create(Image *image)
+{
+  return nullptr;
+}
+
+void BKE_image_partial_update_free(PartialUpdateUser *user)
+{
+}
+
+bool BKE_image_partial_update_collect_tiles(Image *image, PartialUpdateUser *user)
+{
+  user->clear_updated_tiles();
+  PartialUpdateImage *partial_updater = nullptr;  //*image->partial_updater;
+  partial_updater->ensure_empty_transaction();
+
+  if (user->last_transaction_id < partial_updater->first_transaction_id) {
+    user->last_transaction_id = partial_updater->current_transaction_id;
+    return NEED_FULL_UPDATE;
+  }
+
+  if (user->last_transaction_id == partial_updater->current_transaction_id) {
+    // No changes since last time.
+    return NO_CHANGES_SINCE_LAST_TIME;
+  }
+
+  // TODO: Collect changes between last_transaction_id and current_transaction_id.
+  // TODO: compress neighboring tiles and store in user.
+
+  user->last_transaction_id = partial_updated->current_transaction_id;
+  return CHANGES_DETECTED;
+}
+
+bool BKE_image_partial_update_get_tile(PartialUpdateUser *user,
+                                       int index,
+                                       PartialUpdateTile *r_tile)
+{
+  return NO_TILES_LEFT;
+}
+
+}
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