Selecting Fluid>Mesh>"Use Speed Vectors" deletes all existing cache without warning #76881

New Issue

Nicola De Mitri · 2020-05-19T12:47:09+02:00

Nicola De Mitri commented

2020-05-19 12:47:09 +02:00

System Information
Operating system: Ubuntu 18.04
Graphics card: Irrelevant

Blender Version
Broken: 2.83 ff7a30d928 18 May 2020

Short description of error

In the "modular cache" fluid workflow, to a certain extent it is expected that (1) fluid, (2) mesh, (3) particles can be set up and baked at separate stages.

However, Fluid > Mesh > Use speed vectors probably requires a special kind of "fluid" cache with speed vectors enabled. Therefore, clicking on "Use Speed Vectors" immediately, and without a warning, deletes the baked cache. This potentially loses hours of compute work.

Exact steps for others to reproduce the error

Open this basic setup

{F8542867}

Bake the Data, then select "Use Speed Vectors". The baked data is gone.

 {F8542868}

Possible solutions

Assuming that a new bake of the data is actually needed in order to have speed vectors available, there are two possible solutions and possibly others:

When the user selects "Use Speed Vectors", instead of deleting the cache, just disable ("grey out") the Bake Mesh button and add a message under it that says "⚠️ Baking the Mesh with speed vectors requires a fresh Data bake". This way the user will decide whether they want to free and re-bake, or just give up speed vectors.
(my preferred option) Add a "generate speed vectors" in the Data Bake section, with a tooltip saying "Needed for mesh motion blur" or similar. If the user hasn't generated the speed vectors, the Mesh>"Use speed vectors" checkbox will be disabled, with a tooltip explaining why.
(this sounds like a temporary solution though) Add a much more aggressive message to the current tooltip: "WARNING: if you check this box, your data bake will be lost"

**System Information** Operating system: Ubuntu 18.04 Graphics card: Irrelevant **Blender Version** Broken: 2.83 ff7a30d92884 18 May 2020 **Short description of error** In the "modular cache" fluid workflow, to a certain extent it is expected that (1) fluid, (2) mesh, (3) particles can be set up and baked at separate stages. However, *Fluid > Mesh > Use speed vectors* probably requires a special kind of "fluid" cache with speed vectors enabled. Therefore, clicking on "Use Speed Vectors" immediately, and without a warning, deletes the baked cache. This potentially loses hours of compute work. **Exact steps for others to reproduce the error** - Open this basic setup ``` {F8542867} ``` - Bake the Data, then select "Use Speed Vectors". The baked data is gone. ``` {F8542868} ``` **Possible solutions** Assuming that a new bake of the data is actually needed in order to have speed vectors available, there are two possible solutions and possibly others: 1. When the user selects "Use Speed Vectors", instead of deleting the cache, just disable ("grey out") the Bake Mesh button and add a message under it that says _"⚠️ Baking the Mesh with speed vectors requires a fresh Data bake"_. This way the user will decide whether they want to free and re-bake, or just give up speed vectors. 2. (my preferred option) Add a "generate speed vectors" in the Data Bake section, with a tooltip saying "Needed for mesh motion blur" or similar. If the user hasn't generated the speed vectors, the Mesh>"Use speed vectors" checkbox will be disabled, with a tooltip explaining why. 3. (this sounds like a temporary solution though) Add a much more aggressive message to the current tooltip: "WARNING: if you check this box, your data bake will be lost"

Nicola De Mitri commented

2020-05-19 12:47:09 +02:00

Added subscriber: @NicolaSap