VSE: No simultaneous strip snapping on left & right side [and right side favoured] #90826

New Issue

David Salvo · 2021-08-21T13:11:41+02:00

David Salvo commented

2021-08-21 13:11:41 +02:00

System Information
Operating system: Linux-5.4.0-81-generic-x86_64-with-glibc2.31 64 Bits
Graphics card: GeForce 9800 GT/PCIe/SSE2 NVIDIA Corporation 3.3.0 NVIDIA 340.108

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-08-18 20:22, hash: a217e043be
Worked: Unsure

Short description of error
{F10300365,size=full}
A strip in VSE cannot snap at left and right ends simultaneously. Annoying when the end that does not snap is the end that you're wanting to know the orientation of (especially when you're zoomed out and can't tell by eye).

Further to this, the right side snap will always prefer over the left. It seems it just searches the right side first, and if it snaps it just doesn't check the left side at all. I would find it very odd if dual snapping isn't intended, but if somehow there is no plan to add it in the near future, at least the behaviour should not prefer one side - like maybe prefer the side based on the direction the strip is dragged or something (snap first to the side of the direction the strip is heading?).

Exact steps for others to reproduce the error
strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred.blend

Open the blend file, and drag colour strip along x-axis
Only the right end will snap, despite both ends clearly lining up with the metastrips
NOTE: There is a reason I used a metastrip as the snap-to strips here, as there is another snapping bug I will be filing soon (and I didn't want that bug to mess up the behaviour in this one).

**System Information** Operating system: Linux-5.4.0-81-generic-x86_64-with-glibc2.31 64 Bits Graphics card: GeForce 9800 GT/PCIe/SSE2 NVIDIA Corporation 3.3.0 NVIDIA 340.108 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-08-18 20:22, hash: `a217e043be` Worked: Unsure **Short description of error** {[F10300365](https://archive.blender.org/developer/F10300365/no-dual-strip-snapping.png),size=full} A strip in VSE cannot snap at left and right ends simultaneously. Annoying when the end that does not snap is the end that you're wanting to know the orientation of (especially when you're zoomed out and can't tell by eye). Further to this, the right side snap will always prefer over the left. It seems it just searches the right side first, and if it snaps it just doesn't check the left side at all. I would find it very odd if dual snapping isn't intended, but if somehow there is no plan to add it in the near future, at least the behaviour should not prefer one side - like maybe prefer the side based on the direction the strip is dragged or something (snap first to the side of the direction the strip is heading?). **Exact steps for others to reproduce the error** [strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred.blend](https://archive.blender.org/developer/F10300368/strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred.blend) - Open the blend file, and drag colour strip along x-axis - Only the right end will snap, despite both ends clearly lining up with the metastrips NOTE: There is a reason I used a metastrip as the snap-to strips here, as there is another snapping bug I will be filing soon (and I didn't want that bug to mess up the behaviour in this one).

David Salvo commented

2021-08-21 13:11:41 +02:00

Added subscriber: @slinkeepie

Philipp Oeser commented

2021-08-23 13:40:20 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-08-23 13:40:20 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Philipp Oeser commented

2021-08-23 13:40:20 +02:00

Not sure I understand correctly.

In your example the strips are positioned so that snapping the right end to the end of the strip below will have exactly the same outcome as snapping the left end to the start of the strip above.
It is true, in this case you dont get the "dual-snapping-lines".
If I move the meta above slightly by one frame on do it again, I can see it snap to both ends.

strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend

So I dont see the advantage of displaying both snapping borders if they are exactly lined up? The result of the snapping is correct, no?
Could you elaborate?

Not sure I understand correctly. In your example the strips are positioned so that snapping the right end to the end of the strip below will have exactly the same outcome as snapping the left end to the start of the strip above. It is true, in this case you dont get the "dual-snapping-lines". If I move the meta above slightly by one frame on do it again, I can see it snap to both ends. [strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend](https://archive.blender.org/developer/F10311304/strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend) So I dont see the advantage of displaying both snapping borders if they are exactly lined up? The result of the snapping is correct, no? Could you elaborate?

David Salvo commented

2021-08-23 15:15:10 +02:00

In #90826#1210280, @lichtwerk wrote:
Not sure I understand correctly.

In your example the strips are positioned so that snapping the right end to the end of the strip below will have exactly the same outcome as snapping the left end to the start of the strip above.
It is true, in this case you dont get the "dual-snapping-lines".
If I move the meta above slightly by one frame on do it again, I can see it snap to both ends.

strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend

So I dont see the advantage of displaying both snapping borders if they are exactly lined up? The result of the snapping is correct, no?
Could you elaborate?

Hey Philipp, thanks for taking a look...
Quite simply, at distant zoom rates on a large project it can be very hard to tell. Granted, usually there won't be snap points lining up with both edges of a strip, but it does happen - and if the side you're expecting to/trying to snap does not snap, you're unsure if the other one is in line or a frame off.

At the very least, it shouldn't just always prefer the right side (which it does) - there should be some priority given based on a rule of some sort: either based on front or back handle (relative to direction), or honestly if it is going to always prefer one side, shouldn't it be the left side? (since strips start from the left, and it is the side most people aim to line up).

> In #90826#1210280, @lichtwerk wrote: > Not sure I understand correctly. > > In your example the strips are positioned so that snapping the right end to the end of the strip below will have exactly the same outcome as snapping the left end to the start of the strip above. > It is true, in this case you dont get the "dual-snapping-lines". > If I move the meta above slightly by one frame on do it again, I can see it snap to both ends. > > [strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend](https://archive.blender.org/developer/F10311304/strips-do-not-snap-at-both-ends-simultaneously-and-right-side-is-preferred-repro.blend) > > So I dont see the advantage of displaying both snapping borders if they are exactly lined up? The result of the snapping is correct, no? > Could you elaborate? Hey Philipp, thanks for taking a look... Quite simply, at distant zoom rates on a large project it can be very hard to tell. Granted, usually there won't be snap points lining up with both edges of a strip, but it does happen - and if the side you're expecting to/trying to snap does not snap, you're unsure if the other one is in line or a frame off. At the very least, it shouldn't just always prefer the right side (which it does) - there should be some priority given based on a rule of some sort: either based on front or back handle (relative to direction), or honestly if it is going to always prefer one side, shouldn't it be the left side? (since strips start from the left, and it is the side most people aim to line up).

Philipp Oeser commented

2021-08-23 15:37:07 +02:00

Changed status from 'Needs User Info' to: 'Needs Developer To Reproduce'

Philipp Oeser commented

2021-08-23 15:37:07 +02:00

Added subscribers: @iss, @mano-wii

Philipp Oeser commented

2021-08-23 15:37:07 +02:00

OK, thx getting back.
Pretty sure this will not be considered a bug, but I understand your point now (also agree to your suggested improvements: right vs. left and prio based on direction).

Will leave this up to module-devs to classify.

CC @iss
CC @mano-wii

OK, thx getting back. Pretty sure this will not be considered a bug, but I understand your point now (also agree to your suggested improvements: right vs. left and prio based on direction). Will leave this up to module-devs to classify. CC @iss CC @mano-wii

Germano Cavalcante commented

2021-08-23 17:07:28 +02:00

It's more of a design issue.
I see two solutions:

Complex: Draw all snap points.
Simple: Prioritize snap drawing where the strip is approaching.

This would be the simple solution change:

diff --git a/source/blender/editors/transform/transform_snap_sequencer.c b/source/blender/editors/transform/transform_snap_sequencer.c
index 6e926f36fba..079b4d32719 100644
--- a/source/blender/editors/transform/transform_snap_sequencer.c
+++ b/source/blender/editors/transform/transform_snap_sequencer.c
@@ -299,9 +299,9 @@ bool transform_snap_sequencer_calc(TransInfo *t)
   }
 
   int best_dist = MAXFRAME, best_target_frame = 0, best_source_frame = 0;
-
+  const float delta = t->values[0];
   for (int i = 0; i < snap_data->source_snap_point_count; i++) {
-    int snap_source_frame = snap_data->source_snap_points[i] + round_fl_to_int(t->values[0]);
+    int snap_source_frame = snap_data->source_snap_points[i] + round_fl_to_int(delta);
     for (int j = 0; j < snap_data->target_snap_point_count; j++) {
       int snap_target_frame = snap_data->target_snap_points[j];
 
@@ -309,6 +309,13 @@ bool transform_snap_sequencer_calc(TransInfo *t)
       if (dist > best_dist) {
         continue;
       }
+      else if (dist == best_dist) {
+        bool is_start_point = i % 2;
+        if (is_start_point != (delta > 0.0f)) {
+          /* Prioritize snap where elements are approaching. */
+          continue;
+        }
+      }
 
       best_dist = dist;
       best_target_frame = snap_target_frame;

But perhaps it is preferable to invest in the complex solution.

It's more of a design issue. I see two solutions: - Complex: Draw all snap points. - Simple: Prioritize snap drawing where the strip is approaching. This would be the simple solution change: ``` diff --git a/source/blender/editors/transform/transform_snap_sequencer.c b/source/blender/editors/transform/transform_snap_sequencer.c index 6e926f36fba..079b4d32719 100644 --- a/source/blender/editors/transform/transform_snap_sequencer.c +++ b/source/blender/editors/transform/transform_snap_sequencer.c @@ -299,9 +299,9 @@ bool transform_snap_sequencer_calc(TransInfo *t) } int best_dist = MAXFRAME, best_target_frame = 0, best_source_frame = 0; - + const float delta = t->values[0]; for (int i = 0; i < snap_data->source_snap_point_count; i++) { - int snap_source_frame = snap_data->source_snap_points[i] + round_fl_to_int(t->values[0]); + int snap_source_frame = snap_data->source_snap_points[i] + round_fl_to_int(delta); for (int j = 0; j < snap_data->target_snap_point_count; j++) { int snap_target_frame = snap_data->target_snap_points[j]; @@ -309,6 +309,13 @@ bool transform_snap_sequencer_calc(TransInfo *t) if (dist > best_dist) { continue; } + else if (dist == best_dist) { + bool is_start_point = i % 2; + if (is_start_point != (delta > 0.0f)) { + /* Prioritize snap where elements are approaching. */ + continue; + } + } best_dist = dist; best_target_frame = snap_target_frame; ``` But perhaps it is preferable to invest in the complex solution.

Richard Antalik commented

2021-08-25 03:37:15 +02:00

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Richard Antalik commented

2021-08-25 03:37:15 +02:00

In #90826#1210388, @mano-wii wrote:
This would be the simple solution change:

I don't quite like this solution, because it would look like the strip is smaller if it snaps to strip with same length. Probably drawing all snap points is better here. I will confirm though since there may be more issues with snapping that are not neccesarily bugs, and I want to track these.

> In #90826#1210388, @mano-wii wrote: > This would be the simple solution change: I don't quite like this solution, because it would look like the strip is smaller if it snaps to strip with same length. Probably drawing all snap points is better here. I will confirm though since there may be more issues with snapping that are not neccesarily bugs, and I want to track these.

Richard Antalik commented

2021-11-03 04:49:26 +01:00

Will classify this as known issue for now. This has to be discussed or evaluated first.

Philipp Oeser removed the

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

VSE: No simultaneous strip snapping on left & right side [and right side favoured] #90826