GPencil: GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned #87790

New Issue

Maurizio Memoli · 2021-04-25T07:41:04+02:00

Maurizio Memoli commented

2021-04-25 07:41:04 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71

Blender Version
Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-04-21 20:15, hash: 0f66dbea90
Worked: (newest version of Blender that worked as expected)

Short description of error
GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned

Exact steps for others to reproduce the error
Create a Grease pencil stroke.
Create a vertex group
In a text window create a new file and run the following script

import bpy
ob = bpy.context.active_object
gpd = ob.data
gps = gpd.layers[1].frames[0].strokes[0]
i = 0
for pt in gps.points:
    weight = gps.points.weight_get(vertex_group_index=0, point_index=i)
    print(weight)

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71 **Blender Version** Broken: version: 2.93.0 Beta, branch: master, commit date: 2021-04-21 20:15, hash: `0f66dbea90` Worked: (newest version of Blender that worked as expected) **Short description of error** GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned **Exact steps for others to reproduce the error** Create a Grease pencil stroke. Create a vertex group In a text window create a new file and run the following script ``` import bpy ob = bpy.context.active_object gpd = ob.data gps = gpd.layers[1].frames[0].strokes[0] i = 0 for pt in gps.points: weight = gps.points.weight_get(vertex_group_index=0, point_index=i) print(weight) ```

Maurizio Memoli commented

2021-04-25 07:41:04 +02:00

Added subscriber: @maumemoli

Antonio Vazquez commented

2021-04-25 21:34:28 +02:00

Added subscriber: @antoniov

Antonio Vazquez commented

2021-04-25 21:34:28 +02:00

The python api is not designed to check if the data is valid or not, just try to get the data.

I have checked and the first message is: "Groups: No groups for this stroke" The reason is the stroke hasn't any group, only the object.

If you assign a weight to the stroke, then you need pass the correct index. If the index is incorrect, you get the mensaje: "GPencilStrokePoints: index out of range"

This is the underlying C code:

BKE_report(reports, RPT_ERROR, "GPencilStrokePoints: index out of range");
return -1.0f;
}```


In any case, your script has `i += 1` missing:

```import bpy
ob = bpy.context.active_object
gpd = ob.data
gps = gpd.layers- [x].frames- [x].strokes[0]
i = 0
for pt in gps.points:

weight = gps.points.weight_get(vertex_group_index=0, point_index=i)
print(i, weight)
i += 1```

The python api is not designed to check if the data is valid or not, just try to get the data. I have checked and the first message is: "Groups: No groups for this stroke" The reason is the stroke hasn't any group, only the object. If you assign a weight to the stroke, then you need pass the correct index. If the index is incorrect, you get the mensaje: "GPencilStrokePoints: index out of range" This is the underlying C code: ```if (stroke->totpoints <= point_index || point_index < 0) { ``` BKE_report(reports, RPT_ERROR, "GPencilStrokePoints: index out of range"); return -1.0f; }``` ``` In any case, your script has `i += 1` missing: ```import bpy ob = bpy.context.active_object gpd = ob.data gps = gpd.layers- [x].frames- [x].strokes[0] i = 0 for pt in gps.points: ``` weight = gps.points.weight_get(vertex_group_index=0, point_index=i) print(i, weight) i += 1```

Antonio Vazquez commented

2021-04-25 21:36:20 +02:00

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

Antonio Vazquez changed title from ~~GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned~~ to GPencil: GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned

2021-04-25 21:36:47 +02:00

Maurizio Memoli commented

2021-04-25 22:14:44 +02:00

I understand what you mean and I think it should work that way
Now my question is on how I can check if the strokePoints I am iterating are assigned to a vertex group without getting any error.
I guess it is complicated to have the vertex groups values available in the strokePoints as it is for vertices.
Shall I just use a "try" and let it continue if there is a exception?
Any help is really appreciated.

I understand what you mean and I think it should work that way Now my question is on how I can check if the strokePoints I am iterating are assigned to a vertex group without getting any error. I guess it is complicated to have the vertex groups values available in the strokePoints as it is for vertices. Shall I just use a "try" and let it continue if there is a exception? Any help is really appreciated.

Philipp Oeser commented

2021-05-07 14:26:58 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-05-07 14:26:58 +02:00

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

Philipp Oeser closed this issue

2021-05-07 14:26:58 +02:00

Philipp Oeser commented

2021-05-07 14:26:58 +02:00

As soon as any point has a weight assigned, the unassigned will return a value of -1.0.
Only if none is assigned at all, you'll get the Error: Groups: index out of range.

So you are probably best of doing a check prior to the loop if any points are in the group [try/except is not nice, but possibly your best friend here].

Then if that check succeeds, you should be able to loop over all points (and the ones returning -1.0 weight are not assigned).

Mesh vertices have the groups property (https://docs.blender.org/api/master/bpy.types.MeshVertex.html#bpy.types.MeshVertex.groups) which can be utalized in similar mesh cases, maybe that should be implemented for stroke points at some point, I would not consider the current behavior a bug though, will archive for now (of course feel free to comment again if issues persist).

As soon as any point has a weight assigned, the unassigned will return a value of -1.0. Only if none is assigned at all, you'll get the `Error: Groups: index out of range`. So you are probably best of doing a check prior to the loop if any points are in the group [try/except is not nice, but possibly your best friend here]. Then if that check succeeds, you should be able to loop over all points (and the ones returning -1.0 weight are not assigned). Mesh vertices have the `groups` property (https://docs.blender.org/api/master/bpy.types.MeshVertex.html#bpy.types.MeshVertex.groups) which can be utalized in similar mesh cases, maybe that should be implemented for stroke points at some point, I would not consider the current behavior a bug though, will archive for now (of course feel free to comment again if issues persist).

Maurizio Memoli commented

2021-05-07 18:28:25 +02:00

I agree with you Philippe,
this is more of a feature request. I guess I will go with the try, except solution.
Thank you for the help.

I agree with you Philippe, this is more of a feature request. I guess I will go with the try, except solution. Thank you for the help.

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

GPencil: GPencilStrokePoints.weight_get throws an "index out of range" error for Vertex groups IDs with no points assigned #87790