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Goal Strength parameter in “Soft Body Goal” works differently in 2.76+ versions
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Description

System Information
Microsoft Windows 7 sp1, Radeon R9 280x

Blender Version
Broken: 2.76 48f7dd6, and all newer (2.76a, 2.76b, 2.77, 2.77a) up to 2.78 4bb1e22
Worked: 2.75a c27589e and earlier

Short description of error
Goal Strength parameter in “Soft Body Goal” works differently in 2.76+ versions

Exact steps for others to reproduce the error
Parameter "Soft Body Goal > Goal Strength" greatly changed its influence from version 2.76.
For example, in new project: 0) del cube

  1. Add > Mesh > Plane, Subdivide it 3 times in Edit Mode
  2. Select 4 vertexes on corners and Assign to new Vertex Group
  3. Enable "Soft Body" in "Physics" pane
  4. In "Soft Body Goal" select created Vertex Group (all settings by default, nothing change in any field)
  5. Play animation

Problem: in Blender 2.75 and earlier (tested up to 2.71) animation is almost flat, slightly fluctuation. In Blender 2.76 and newer (tested up to 2.78) animation looks like long rubber deformation with big amplitude. At least "Goal Strength" parameter in “Soft Body Goal” change its influence when going from 2.75 to 2.76+.

soft_body_goal_275.blend453 KBDownload

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Event Timeline

Dmitry (dmlesk) created this task.Oct 13 2016, 9:15 PM
Dmitry (dmlesk) updated the task description. (Show Details)Oct 13 2016, 9:20 PM
Bastien Montagne (mont29) removed Dmitry (dmlesk) as the assignee of this task.Oct 14 2016, 12:42 PM
Bastien Montagne (mont29) lowered the priority of this task from 90 to 30.
Bastien Montagne (mont29) added a subscriber: Bastien Montagne (mont29).

That’s going to be hard to find the what/who/where/why, with such an old change… And change in behavior does not mean it’s a bug even? To me current behavior sounds rather OK?

Dmitry (dmlesk) added a comment.EditedOct 14 2016, 3:35 PM

Yes, maybe it's not a bug. Behavior similar to earlier versions can be achieved by setting "1" in "Goal Strength > Default" field after selection Vertex Group. Other vertexes now can be managed in fields "Minimum-Maximum" instead "Default" in earlier versions.

Bastien Montagne (mont29) changed the task status from Unknown Status to Archived.Oct 14 2016, 4:34 PM
Bastien Montagne (mont29) claimed this task.

The change was made on purpose in rB240646f5068, to make it more consistent with other vgroups-used-as-factors usages across Blender (unassigned weights are set to minimal goal weight). Agree change should have been documented in release notes, but there is no bug here. Thanks for the report anyway.