NLA: Extract ..get_inverted_upper_snapshot()

Extracts `nlasnapshot_blend_get_inverted_upper_snapshot()` from
`BKE_animsys_nla_remap_keyframe_values()`

This introduces a new struct member:
`NlaEvalChannelSnapshot->remap_domain` and marks which values of
`blended_snapshot` are processed for remapping/used-for-inverting.
Effectively, it marks which values have successfully been remapped and
can be further used for remapping.

`nlasnapshot_blend_get_inverted_upper_snapshot()`:
output snapshot `r_upper_snapshot` has each channel's `remap_domain`
written to which effectively marks the successfully remapped values.
The only reason a value is not in the remap domain is if inversion
failed or it wasn't marked to be remapped.

`..get_inverted_upper_snapshot()` has a variant `nlasnapshot_blend()`
from {D10220}, but this patch doesn't depend on it at all. A third
variant will later be added `..get_inverted_lower_snapshot()`.
Altogether, these three functions allow solving for any of
(lower_snapshot, upper_snapshot, blended_snapshot) given the other two.
The function `..get_inverted_lower_snapshot()` will also similarly
process the remap domain of the blended and lower snapshot.

added assertions within `nlasnapshot_blend()` and
`..get_inverted_upper_snapshot()` to future proof branches dealing with
blendmode and mixmodes. (suggested by sybren)

No user functional changes

Reviewed By: sybren

Differential Revision: https://developer.blender.org/D10222

2 files changed, 431 insertions, 89 deletions

diff --git a/source/blender/blenkernel/intern/anim_sys.c b/source/blender/blenkernel/intern/anim_sys.c
index 6f4af6f655d..564b5c9399a 100644
--- a/source/blender/blenkernel/intern/anim_sys.c
+++ b/source/blender/blenkernel/intern/anim_sys.c
@@ -1040,6 +1040,7 @@ static NlaEvalChannelSnapshot *nlaevalchan_snapshot_new(NlaEvalChannel *nec)
   nec_snapshot->channel = nec;
   nec_snapshot->length = length;
   nlavalidmask_init(&nec_snapshot->blend_domain, length);
+  nlavalidmask_init(&nec_snapshot->remap_domain, length);
 
   return nec_snapshot;
 }
@@ -1050,6 +1051,7 @@ static void nlaevalchan_snapshot_free(NlaEvalChannelSnapshot *nec_snapshot)
   BLI_assert(!nec_snapshot->is_base);
 
   nlavalidmask_free(&nec_snapshot->blend_domain);
+  nlavalidmask_free(&nec_snapshot->remap_domain);
   MEM_freeN(nec_snapshot);
 }
 
@@ -1650,6 +1652,355 @@ static bool nla_combine_quaternion_get_inverted_strip_values(const float lower_v
 }
 
 /* ---------------------- */
+
+/* Assert necs and necs->channel is nonNull. */
+static void nlaevalchan_assert_nonNull(NlaEvalChannelSnapshot *necs)
+{
+  UNUSED_VARS_NDEBUG(necs);
+  BLI_assert(necs != NULL && necs->channel != NULL);
+}
+
+/* Assert that the channels given can be blended or combined together. */
+static void nlaevalchan_assert_blendOrcombine_compatible(NlaEvalChannelSnapshot *lower_necs,
+                                                         NlaEvalChannelSnapshot *upper_necs,
+                                                         NlaEvalChannelSnapshot *blended_necs)
+{
+  UNUSED_VARS_NDEBUG(lower_necs, upper_necs, blended_necs);
+  BLI_assert(!ELEM(NULL, lower_necs, blended_necs));
+  BLI_assert(upper_necs == NULL || lower_necs->length == upper_necs->length);
+  BLI_assert(lower_necs->length == blended_necs->length);
+}
+
+/* Assert that the channels given can be blended or combined together as a quaternion. */
+static void nlaevalchan_assert_blendOrcombine_compatible_quaternion(
+    NlaEvalChannelSnapshot *lower_necs,
+    NlaEvalChannelSnapshot *upper_necs,
+    NlaEvalChannelSnapshot *blended_necs)
+{
+  nlaevalchan_assert_blendOrcombine_compatible(lower_necs, upper_necs, blended_necs);
+  BLI_assert(lower_necs->length == 4);
+}
+
+static void nlaevalchan_copy_values(NlaEvalChannelSnapshot *dst, NlaEvalChannelSnapshot *src)
+{
+  memcpy(dst->values, src->values, src->length * sizeof(float));
+}
+
+/** Copies lower necs to blended necs if upper necs is NULL or has zero influence.
+ * \return true if copied. */
+static bool nlaevalchan_blendOrcombine_try_copy_lower(NlaEvalChannelSnapshot *lower_necs,
+                                                      NlaEvalChannelSnapshot *upper_necs,
+                                                      const float upper_influence,
+                                                      NlaEvalChannelSnapshot *r_blended_necs)
+{
+  const bool has_influence = !IS_EQF(upper_influence, 0.0f);
+  if (upper_necs != NULL && has_influence) {
+    return false;
+  }
+
+  nlaevalchan_copy_values(r_blended_necs, lower_necs);
+  return true;
+}
+
+/** Based on blendmode, blend lower necs with upper necs into blended necs.
+ *
+ * Each upper value's blend domain determines whether to blend or to copy directly
+ * from lower.
+ */
+static void nlaevalchan_blend_value(NlaEvalChannelSnapshot *lower_necs,
+                                    NlaEvalChannelSnapshot *upper_necs,
+                                    const int upper_blendmode,
+                                    const float upper_influence,
+                                    NlaEvalChannelSnapshot *r_blended_necs)
+{
+  nlaevalchan_assert_blendOrcombine_compatible(lower_necs, upper_necs, r_blended_necs);
+  if (nlaevalchan_blendOrcombine_try_copy_lower(
+          lower_necs, upper_necs, upper_influence, r_blended_necs)) {
+    return;
+  }
+
+  const int length = lower_necs->length;
+  for (int j = 0; j < length; j++) {
+    if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, j)) {
+      r_blended_necs->values[j] = lower_necs->values[j];
+      continue;
+    }
+
+    r_blended_necs->values[j] = nla_blend_value(
+        upper_blendmode, lower_necs->values[j], upper_necs->values[j], upper_influence);
+  }
+}
+
+/** Based on mixmode, provided by one the necs, combines lower necs with upper necs into blended
+ * necs.
+ *
+ * Each upper value's blend domain determines whether to blend or to copy directly
+ * from lower.
+ */
+static void nlaevalchan_combine_value(NlaEvalChannelSnapshot *lower_necs,
+                                      NlaEvalChannelSnapshot *upper_necs,
+                                      const float upper_influence,
+                                      NlaEvalChannelSnapshot *r_blended_necs)
+{
+  nlaevalchan_assert_blendOrcombine_compatible(lower_necs, upper_necs, r_blended_necs);
+  if (nlaevalchan_blendOrcombine_try_copy_lower(
+          lower_necs, upper_necs, upper_influence, r_blended_necs)) {
+    return;
+  }
+
+  /* Assumes every base is the same. */
+  float *base_values = lower_necs->channel->base_snapshot.values;
+  const int length = lower_necs->length;
+  const char mix_mode = lower_necs->channel->mix_mode;
+
+  for (int j = 0; j < length; j++) {
+    if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, j)) {
+      r_blended_necs->values[j] = lower_necs->values[j];
+      continue;
+    }
+
+    r_blended_necs->values[j] = nla_combine_value(
+        mix_mode, base_values[j], lower_necs->values[j], upper_necs->values[j], upper_influence);
+  }
+}
+
+/** Quaternion combines lower necs with upper necs into blended necs.
+ *
+ * Each upper value's blend domain determines whether to blend or to copy directly
+ * from lower.
+ */
+static void nlaevalchan_combine_quaternion(NlaEvalChannelSnapshot *lower_necs,
+                                           NlaEvalChannelSnapshot *upper_necs,
+                                           const float upper_influence,
+                                           NlaEvalChannelSnapshot *r_blended_necs)
+{
+  nlaevalchan_assert_blendOrcombine_compatible_quaternion(lower_necs, upper_necs, r_blended_necs);
+  if (nlaevalchan_blendOrcombine_try_copy_lower(
+          lower_necs, upper_necs, upper_influence, r_blended_necs)) {
+    return;
+  }
+
+  /** No need to check per index. We limit to all or nothing combining for quaternions. */
+  if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, 0)) {
+    nlaevalchan_copy_values(r_blended_necs, lower_necs);
+    return;
+  }
+
+  nla_combine_quaternion(
+      lower_necs->values, upper_necs->values, upper_influence, r_blended_necs->values);
+}
+
+/** Based on blendmode and mixmode, blend lower necs with upper necs into blended necs.
+ *
+ * Each upper value's blend domain determines whether to blend or to copy directly
+ * from lower.
+ *
+ * \param lower_necs: Never NULL.
+ * \param upper_necs: Can be NULL.
+ * \param upper_blendmode: Enum value in eNlaStrip_Blend_Mode.
+ * \param upper_influence: Value in range [0, 1].
+ * \param upper_necs: Never NULL.
+ *
+ */
+static void nlaevalchan_blendOrcombine(NlaEvalChannelSnapshot *lower_necs,
+                                       NlaEvalChannelSnapshot *upper_necs,
+                                       const int upper_blendmode,
+                                       const float upper_influence,
+                                       NlaEvalChannelSnapshot *r_blended_necs)
+{
+  nlaevalchan_assert_nonNull(r_blended_necs);
+
+  switch (upper_blendmode) {
+    case NLASTRIP_MODE_COMBINE: {
+      switch (r_blended_necs->channel->mix_mode) {
+        case NEC_MIX_QUATERNION: {
+          nlaevalchan_combine_quaternion(lower_necs, upper_necs, upper_influence, r_blended_necs);
+          return;
+        }
+        case NEC_MIX_ADD:
+        case NEC_MIX_AXIS_ANGLE:
+        case NEC_MIX_MULTIPLY: {
+          nlaevalchan_combine_value(lower_necs, upper_necs, upper_influence, r_blended_necs);
+          return;
+        }
+        default:
+          BLI_assert("Mix mode should've been handled");
+      }
+      return;
+    }
+    case NLASTRIP_MODE_ADD:
+    case NLASTRIP_MODE_SUBTRACT:
+    case NLASTRIP_MODE_MULTIPLY:
+    case NLASTRIP_MODE_REPLACE: {
+      nlaevalchan_blend_value(
+          lower_necs, upper_necs, upper_blendmode, upper_influence, r_blended_necs);
+      return;
+    }
+    default:
+      BLI_assert("Blend mode should've been handled");
+  }
+}
+
+/** Based on blendmode, solve for the upper values such that when lower blended with upper then we
+ * get blended values as a result.
+ *
+ * Only processes blended values in the remap domain. Successfully remapped upper values are placed
+ * in the remap domain so caller knows which values are usable.
+ */
+static void nlaevalchan_blend_value_get_inverted_upper_evalchan(
+    NlaEvalChannelSnapshot *lower_necs,
+    NlaEvalChannelSnapshot *blended_necs,
+    const int upper_blendmode,
+    const float upper_influence,
+    NlaEvalChannelSnapshot *r_upper_necs)
+{
+  nlaevalchan_assert_nonNull(r_upper_necs);
+  nlaevalchan_assert_blendOrcombine_compatible(lower_necs, r_upper_necs, blended_necs);
+
+  const int length = lower_necs->length;
+  for (int j = 0; j < length; j++) {
+    if (!BLI_BITMAP_TEST_BOOL(blended_necs->remap_domain.ptr, j)) {
+      BLI_BITMAP_DISABLE(r_upper_necs->remap_domain.ptr, j);
+      continue;
+    }
+
+    const bool success = nla_blend_get_inverted_strip_value(upper_blendmode,
+                                                            lower_necs->values[j],
+                                                            blended_necs->values[j],
+                                                            upper_influence,
+                                                            &r_upper_necs->values[j]);
+    BLI_BITMAP_SET(r_upper_necs->remap_domain.ptr, j, success);
+  }
+}
+
+/** Based on mixmode, solve for the upper values such that when lower combined with upper then we
+ * get blended values as a result.
+ *
+ * Only processes blended values in the remap domain. Successfully remapped upper values are placed
+ * in the remap domain so caller knows which values are usable.
+ */
+static void nlaevalchan_combine_value_get_inverted_upper_evalchan(
+    NlaEvalChannelSnapshot *lower_necs,
+    NlaEvalChannelSnapshot *blended_necs,
+    const float upper_influence,
+    NlaEvalChannelSnapshot *r_upper_necs)
+{
+  nlaevalchan_assert_nonNull(r_upper_necs);
+  nlaevalchan_assert_blendOrcombine_compatible(lower_necs, r_upper_necs, blended_necs);
+
+  /* Assumes every channel's base is the same. */
+  float *base_values = lower_necs->channel->base_snapshot.values;
+  const int length = lower_necs->length;
+  const char mix_mode = lower_necs->channel->mix_mode;
+
+  for (int j = 0; j < length; j++) {
+    if (!BLI_BITMAP_TEST_BOOL(blended_necs->remap_domain.ptr, j)) {
+      BLI_BITMAP_DISABLE(r_upper_necs->remap_domain.ptr, j);
+      continue;
+    }
+
+    const bool success = nla_combine_get_inverted_strip_value(mix_mode,
+                                                              base_values[j],
+                                                              lower_necs->values[j],
+                                                              blended_necs->values[j],
+                                                              upper_influence,
+                                                              &r_upper_necs->values[j]);
+
+    BLI_BITMAP_SET(r_upper_necs->remap_domain.ptr, j, success);
+  }
+}
+
+/** Solve for the upper values such that when lower quaternion combined with upper then we get
+ * blended values as a result.
+ *
+ * All blended values must be in the remap domain. If successfully remapped, then all upper values
+ * are placed in the remap domain so caller knows the result is usable.
+ */
+static void nlaevalchan_combine_quaternion_get_inverted_upper_evalchan(
+    NlaEvalChannelSnapshot *lower_necs,
+    NlaEvalChannelSnapshot *blended_necs,
+    const float upper_influence,
+    NlaEvalChannelSnapshot *r_upper_necs)
+{
+  nlaevalchan_assert_nonNull(r_upper_necs);
+  nlaevalchan_assert_blendOrcombine_compatible_quaternion(lower_necs, r_upper_necs, blended_necs);
+
+  /* Must check each domain index individually in case animator had a non-combine NLA strip with a
+   * subset of quaternion channels and remapping through any of them failed and thus potentially
+   * has undefined values. */
+  for (int j = 0; j < 4; j++) {
+    if (!BLI_BITMAP_TEST_BOOL(blended_necs->remap_domain.ptr, j)) {
+      BLI_bitmap_set_all(r_upper_necs->remap_domain.ptr, false, 4);
+      return;
+    }
+  }
+
+  const bool success = nla_combine_quaternion_get_inverted_strip_values(
+      lower_necs->values, blended_necs->values, upper_influence, r_upper_necs->values);
+
+  BLI_bitmap_set_all(r_upper_necs->remap_domain.ptr, success, 4);
+}
+
+/** Based on blendmode and mix mode, solve for the upper values such that when lower blended or
+ * combined with upper then we get blended values as a result.
+ *
+ * Only processes blended values in the remap domain. Successfully remapped upper values are placed
+ * in the remap domain so caller knows which values are usable.
+ *
+ * \param lower_necs: Never NULL.
+ * \param blended_necs: Never NULL.
+ * \param upper_blendmode: Enum value in eNlaStrip_Blend_Mode.
+ * \param upper_influence: Value in range [0, 1].
+ * \param r_upper_necs: Never NULL.
+ */
+static void nlaevalchan_blendOrcombine_get_inverted_upper_evalchan(
+    NlaEvalChannelSnapshot *lower_necs,
+    NlaEvalChannelSnapshot *blended_necs,
+    const int upper_blendmode,
+    const float upper_influence,
+    NlaEvalChannelSnapshot *r_upper_necs)
+{
+  nlaevalchan_assert_nonNull(r_upper_necs);
+
+  if (IS_EQF(upper_influence, 0.0f)) {
+    BLI_bitmap_set_all(r_upper_necs->remap_domain.ptr, false, r_upper_necs->length);
+    return;
+  }
+
+  switch (upper_blendmode) {
+    case NLASTRIP_MODE_COMBINE: {
+      switch (r_upper_necs->channel->mix_mode) {
+        case NEC_MIX_QUATERNION: {
+          nlaevalchan_combine_quaternion_get_inverted_upper_evalchan(
+              lower_necs, blended_necs, upper_influence, r_upper_necs);
+          return;
+        }
+        case NEC_MIX_ADD:
+        case NEC_MIX_AXIS_ANGLE:
+        case NEC_MIX_MULTIPLY: {
+          nlaevalchan_combine_value_get_inverted_upper_evalchan(
+              lower_necs, blended_necs, upper_influence, r_upper_necs);
+          return;
+        }
+        default:
+          BLI_assert("Mix mode should've been handled");
+      }
+      return;
+    }
+    case NLASTRIP_MODE_ADD:
+    case NLASTRIP_MODE_SUBTRACT:
+    case NLASTRIP_MODE_MULTIPLY:
+    case NLASTRIP_MODE_REPLACE: {
+      nlaevalchan_blend_value_get_inverted_upper_evalchan(
+          lower_necs, blended_necs, upper_blendmode, upper_influence, r_upper_necs);
+      return;
+    }
+    default:
+      BLI_assert("Blend mode should've been handled");
+  }
+}
+
+/* ---------------------- */
 /* F-Modifier stack joining/separation utilities -
  * should we generalize these for BLI_listbase.h interface? */
 
@@ -2513,11 +2864,7 @@ void nlasnapshot_blend(NlaEvalData *eval_data,
 {
   nlaeval_snapshot_ensure_size(r_blended_snapshot, eval_data->num_channels);
 
-  const bool zero_upper_influence = IS_EQF(upper_influence, 0.0f);
-
   LISTBASE_FOREACH (NlaEvalChannel *, nec, &eval_data->channels) {
-    const int length = nec->base_snapshot.length;
-
     NlaEvalChannelSnapshot *upper_necs = nlaeval_snapshot_get(upper_snapshot, nec->index);
     NlaEvalChannelSnapshot *lower_necs = nlaeval_snapshot_get(lower_snapshot, nec->index);
     if (upper_necs == NULL && lower_necs == NULL) {
@@ -2530,49 +2877,43 @@ void nlasnapshot_blend(NlaEvalData *eval_data,
     }
 
     NlaEvalChannelSnapshot *result_necs = nlaeval_snapshot_ensure_channel(r_blended_snapshot, nec);
+    nlaevalchan_blendOrcombine(
+        lower_necs, upper_necs, upper_blendmode, upper_influence, result_necs);
+  }
+}
 
-    /** Always copy \a lower_snapshot to result, irrelevant of whether \a upper_snapshot has a
-     * corresponding channel. This only matters when \a lower_snapshot not the same as
-     * \a r_blended_snapshot. */
-    memcpy(result_necs->values, lower_necs->values, length * sizeof(float));
-    if (upper_necs == NULL || zero_upper_influence) {
+/** Using  \a blended_snapshot and \a lower_snapshot, we can solve for the \a r_upper_snapshot.
+ *
+ * Only channels that exist within \a blended_snapshot are inverted.
+ *
+ * For \a r_upper_snapshot, disables \a NlaEvalChannelSnapshot->remap_domain for failed inversions.
+ * Only values within the \a remap_domain are processed.
+ */
+void nlasnapshot_blend_get_inverted_upper_snapshot(NlaEvalData *eval_data,
+                                                   NlaEvalSnapshot *lower_snapshot,
+                                                   NlaEvalSnapshot *blended_snapshot,
+                                                   const short upper_blendmode,
+                                                   const float upper_influence,
+                                                   NlaEvalSnapshot *r_upper_snapshot)
+{
+  nlaeval_snapshot_ensure_size(r_upper_snapshot, eval_data->num_channels);
+
+  LISTBASE_FOREACH (NlaEvalChannel *, nec, &eval_data->channels) {
+    NlaEvalChannelSnapshot *blended_necs = nlaeval_snapshot_get(blended_snapshot, nec->index);
+    if (blended_necs == NULL) {
+      /** We assume the caller only wants a subset of channels to be inverted, those that exist
+       * within \a blended_snapshot. */
       continue;
     }
 
-    if (upper_blendmode == NLASTRIP_MODE_COMBINE) {
-      const int mix_mode = nec->mix_mode;
-      if (mix_mode == NEC_MIX_QUATERNION) {
-        if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, 0)) {
-          continue;
-        }
-
-        nla_combine_quaternion(
-            lower_necs->values, upper_necs->values, upper_influence, result_necs->values);
-      }
-      else {
-        for (int j = 0; j < length; j++) {
-          if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, j)) {
-            continue;
-          }
-
-          result_necs->values[j] = nla_combine_value(mix_mode,
-                                                     nec->base_snapshot.values[j],
-                                                     lower_necs->values[j],
-                                                     upper_necs->values[j],
-                                                     upper_influence);
-        }
-      }
+    NlaEvalChannelSnapshot *lower_necs = nlaeval_snapshot_get(lower_snapshot, nec->index);
+    if (lower_necs == NULL) {
+      lower_necs = nlaeval_snapshot_find_channel(lower_snapshot->base, nec);
     }
-    else {
-      for (int j = 0; j < length; j++) {
-        if (!BLI_BITMAP_TEST_BOOL(upper_necs->blend_domain.ptr, j)) {
-          continue;
-        }
 
-        result_necs->values[j] = nla_blend_value(
-            upper_blendmode, lower_necs->values[j], upper_necs->values[j], upper_influence);
-      }
-    }
+    NlaEvalChannelSnapshot *result_necs = nlaeval_snapshot_ensure_channel(r_upper_snapshot, nec);
+    nlaevalchan_blendOrcombine_get_inverted_upper_evalchan(
+        lower_necs, blended_necs, upper_blendmode, upper_influence, result_necs);
   }
 }
 
@@ -2670,74 +3011,64 @@ bool BKE_animsys_nla_remap_keyframe_values(struct NlaKeyframingContext *context,
     return false;
   }
 
-  /* Find the evaluation channel for the NLA stack below current strip. */
+  /** Create \a blended_snapshot and fill with input \a values. */
+  NlaEvalData *eval_data = &context->lower_eval_data;
+  NlaEvalSnapshot blended_snapshot;
+  nlaeval_snapshot_init(&blended_snapshot, eval_data, NULL);
+
   NlaEvalChannelKey key = {
       .ptr = *prop_ptr,
       .prop = prop,
   };
-  /**
-   * Remove lower NLA stack effects.
-   *
-   * Using the tweak strip's blended result and the lower snapshot value, we can solve for the
-   * tweak strip value it must evaluate to.
-   */
-  NlaEvalData *const lower_eval_data = &context->lower_eval_data;
-  NlaEvalChannel *const lower_nec = nlaevalchan_verify_key(lower_eval_data, NULL, &key);
 
-  if ((lower_nec->base_snapshot.length != count)) {
+  NlaEvalChannel *nec = nlaevalchan_verify_key(eval_data, NULL, &key);
+  BLI_assert(nec);
+  if (nec->base_snapshot.length != count) {
     BLI_assert(!"invalid value count");
+    nlaeval_snapshot_free_data(&blended_snapshot);
     return false;
   }
 
-  /* Invert the blending operation to compute the desired strip values. */
-  NlaEvalChannelSnapshot *const lower_nec_snapshot = nlaeval_snapshot_find_channel(
-      &lower_eval_data->eval_snapshot, lower_nec);
+  NlaEvalChannelSnapshot *blended_necs = nlaeval_snapshot_ensure_channel(&blended_snapshot, nec);
+  memcpy(blended_necs->values, values, sizeof(float) * count);
+  BLI_bitmap_set_all(blended_necs->remap_domain.ptr, true, count);
 
-  float *lower_values = lower_nec_snapshot->values;
+  /** Remove lower NLA stack effects. */
+  nlasnapshot_blend_get_inverted_upper_snapshot(eval_data,
+                                                &context->lower_eval_data.eval_snapshot,
+                                                &blended_snapshot,
+                                                blend_mode,
+                                                influence,
+                                                &blended_snapshot);
 
-  if (blend_mode == NLASTRIP_MODE_COMBINE) {
-    /* Quaternion combine handles all sub-channels as a unit. */
-    if (lower_nec->mix_mode == NEC_MIX_QUATERNION) {
-      if (r_force_all == NULL) {
-        return false;
-      }
+  /** Write results into \a values. */
+  bool successful_remap = true;
+  if (blended_necs->channel->mix_mode == NEC_MIX_QUATERNION &&
+      blend_mode == NLASTRIP_MODE_COMBINE) {
 
+    if (r_force_all != NULL) {
       *r_force_all = true;
-
-      if (!nla_combine_quaternion_get_inverted_strip_values(
-              lower_values, values, influence, values)) {
-        return false;
-      }
+      index = -1;
     }
     else {
-      float *base_values = lower_nec->base_snapshot.values;
-
-      for (int i = 0; i < count; i++) {
-        if (ELEM(index, i, -1)) {
-          if (!nla_combine_get_inverted_strip_value(lower_nec->mix_mode,
-                                                    base_values[i],
-                                                    lower_values[i],
-                                                    values[i],
-                                                    influence,
-                                                    &values[i])) {
-            return false;
-          }
-        }
-      }
+      successful_remap = false;
     }
   }
-  else {
-    for (int i = 0; i < count; i++) {
-      if (ELEM(index, i, -1)) {
-        if (!nla_blend_get_inverted_strip_value(
-                blend_mode, lower_values[i], values[i], influence, &values[i])) {
-          return false;
-        }
-      }
+
+  for (int i = 0; i < count; i++) {
+    if (!ELEM(index, i, -1)) {
+      continue;
+    }
+    if (!BLI_BITMAP_TEST_BOOL(blended_necs->remap_domain.ptr, i)) {
+      successful_remap = false;
     }
+
+    values[i] = blended_necs->values[i];
   }
 
-  return true;
+  nlaeval_snapshot_free_data(&blended_snapshot);
+
+  return successful_remap;
 }
 
 /**
diff --git a/source/blender/blenkernel/nla_private.h b/source/blender/blenkernel/nla_private.h
index 706bcac4f17..71b5a74ddf7 100644
--- a/source/blender/blenkernel/nla_private.h
+++ b/source/blender/blenkernel/nla_private.h
@@ -82,6 +82,10 @@ typedef struct NlaEvalChannelSnapshot {
   /** For an upper snapshot channel, marks values that should be blended. */
   NlaValidMask blend_domain;
 
+  /** Only used for keyframe remapping. Any values not in the \a remap_domain will not be used
+   * for keyframe remapping. */
+  NlaValidMask remap_domain;
+
   int length;   /* Number of values in the property. */
   bool is_base; /* Base snapshot of the channel. */
 
@@ -196,6 +200,13 @@ void nlasnapshot_blend(NlaEvalData *eval_data,
                        const float upper_influence,
                        NlaEvalSnapshot *r_blended_snapshot);
 
+void nlasnapshot_blend_get_inverted_upper_snapshot(NlaEvalData *eval_data,
+                                                   NlaEvalSnapshot *lower_snapshot,
+                                                   NlaEvalSnapshot *blended_snapshot,
+                                                   const short upper_blendmode,
+                                                   const float upper_influence,
+                                                   NlaEvalSnapshot *r_upper_snapshot);
+
 #ifdef __cplusplus
 }
 #endif