Mantaflow Object Initial Velocity Local Coordinates. #74818

New Issue

RAM · 2020-03-16T17:17:27+01:00

RAM commented

2020-03-16 17:17:27 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: Quadro P4000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.70

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-02-12 16:20, hash: blender/blender@77d23b0bd7

Short description of error
Documentation https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity states that:

Initial Velocity: When enabled, the fluid will inherit the momentum of the flow source.

This is not true for all sub-items - Initial X Y and Z velocity will affect stationary object.

Initial X, Y, Z: Initial velocity along X, Y, Z coordinates. Can be used in addition to the initial velocity along the Normal.

It is not clear in what coordinate space this will affect simulation.

Exact steps for others to reproduce the error
#74818.blend

Open file
Bake and run simulation.

Flow source is rotated and has set initial velocity in Z.
One may expect that flow velocity vector will be affected by flow source rotation.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: Quadro P4000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.70 **Blender Version** Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-02-12 16:20, hash: `blender/blender@77d23b0bd7` **Short description of error** Documentation https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity states that: > Initial Velocity: When enabled, the fluid will inherit the momentum of the flow source. This is not true for all sub-items - Initial X Y and Z velocity will affect stationary object. >Initial X, Y, Z: Initial velocity along X, Y, Z coordinates. Can be used in addition to the initial velocity along the Normal. It is not clear in what coordinate space this will affect simulation. **Exact steps for others to reproduce the error** [#74818.blend](https://archive.blender.org/developer/F8423789/T74818.blend) - Open file - Bake and run simulation. Flow source is rotated and has set initial velocity in Z. One may expect that flow velocity vector will be affected by flow source rotation.

RAM commented

2020-03-16 17:17:27 +01:00

Added subscriber: @CrossmindStudio

Richard Antalik commented

2020-03-17 20:51:43 +01:00

Added subscribers: @sebbas, @iss

Richard Antalik commented

2020-03-17 20:51:43 +01:00

@sebbas It is not clear to me, if this is working as intended, Can you confirm/close this report?

Ankit Meel commented

2020-03-21 08:48:50 +01:00

Added subscriber: @ankitm

Ankit Meel commented

2020-03-21 08:48:50 +01:00

https://developer.blender.org/T72949

Ankit Meel commented

2020-04-20 10:29:07 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Ankit Meel closed this issue

2020-04-20 10:29:07 +02:00

Ankit Meel self-assigned this 2020-04-20 10:29:07 +02:00

Ankit Meel commented

2020-04-20 10:29:07 +02:00

Initial Velocity
When enabled, the fluid will inherit the momentum of the flow source.

So a stationary object will not give a velocity of 2 in any direction.
https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity

> Initial Velocity > When enabled, the fluid will inherit the momentum of the flow source. So a stationary object will not give a velocity of 2 in any direction. https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity

Richard Antalik commented

2020-04-20 13:19:29 +02:00

Changed status from 'Archived' to: 'Confirmed'

Richard Antalik reopened this issue

2020-04-20 13:19:29 +02:00

Richard Antalik commented

2020-04-20 13:19:29 +02:00

In #74818#913855, @ankitm wrote:

Initial Velocity
When enabled, the fluid will inherit the momentum of the flow source.

So a stationary object will not give a velocity of 2 in any direction.
https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity

I will reopen and confirm because this doen't make sense - Setting Z initial velocity has effect on stationary source, but it is not specified in which coordinate space.

So I guess this is double wrong..

> In #74818#913855, @ankitm wrote: >> Initial Velocity >> When enabled, the fluid will inherit the momentum of the flow source. > So a stationary object will not give a velocity of 2 in any direction. > https://docs.blender.org/manual/en/latest/physics/fluid/type/flow.html#initial-velocity I will reopen and confirm because this doen't make sense - Setting Z initial velocity has effect on stationary source, but it is not specified in which coordinate space. So I guess this is double wrong..

Ankit Meel removed their assignment 2020-04-23 08:56:40 +02:00

Jacques Lucke commented

2020-05-12 13:52:32 +02:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2020-05-12 13:52:32 +02:00

The behavior seems to be the same in the old fluids system. Therefore, I think this is not a bug in Blender, but in the documentation (I'll fix that).

We might want to change the behavior at some point, but that is outside of the scope of a bug report.

The behavior seems to be the same in the old fluids system. Therefore, I think this is not a bug in Blender, but in the documentation (I'll fix that). We might want to change the behavior at some point, but that is outside of the scope of a bug report.

blender-admin commented

2020-05-12 13:55:58 +02:00

This issue was referenced by blender/blender@fffcb6e480

This issue was referenced by blender/blender@fffcb6e48068d77de6bbaaf35ef30515d1078dac

Jacques Lucke commented

2020-05-12 13:56:36 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Jacques Lucke closed this issue

2020-05-12 13:56:36 +02:00

Jacques Lucke self-assigned this 2020-05-12 13:56:36 +02:00

blender-admin commented

2020-05-12 14:03:44 +02:00