The problem happens because smoke collides only with the surface of the
collider and uses incompressible fluid solver. This means that scaling
the collider tries to compress or decompress fluid within the volume of
the collider, which can't be handled by the simulation. Fast rotation
likely also causes transient scaling due to emulation of arcs by chords.
This can be fixed by finding compartments completely isolated by obstacles
from the rest of the domain, and forcing total divergence within each one
to be zero so that equations are solvable. Physical validity is somewhat
dubious, but without this the solver simply breaks down.
From the physics point of view, the effect of the correction should be
similar to opening a hole from every cell to another dimension that lets
an equal amount of air to pass through to balance the change in volume.
Reviewers: miikah, lukastoenne
Reviewed By: lukastoenne
Subscribers: dafassi, scorpion81, #physics
Maniphest Tasks: T43220, T47551
Differential Revision: https://developer.blender.org/D2112
This change is for a few reasons:
- it works with color, and (therefore) will need to be color managed, at
some point. This will be much easier to do if the code is closer to the
actual color management code (in Blender's core, so to speak).
- it has nothing to do with the actual fire simulation, as it is just
used to create a lookup table
- it can be reused for other purposes (i.e. in Blender internal
renderer, if people are interrested in a blackbody node à la Cycles)
- cleanup: some functions (`contrain_rgb`, `xyz_to_rgb`) already exist
in BLI
Reviewers: brecht
Reviewed By: brecht
Subscribers: brecht
Differential Revision: https://developer.blender.org/D1719
While SCons building system was serving us really good for ages it's no longer
having much attention by the developers and started to become quite a difficult
task to maintain.
What's even worse -- there started to be quite serious divergence between SCons
and CMake which was only accumulating over the releases now. The fact that none
of the active developers are really using SCons and that our main studio is also
using CMake spotting bugs in the SCons builds became quite a difficult task and
we aren't always spotting them in time.
Meanwhile CMake became really mature building system which is available on every
platform we support and arguably it's also easier and more robust to use.
This commit includes:
- Removal of actual SCons building system
- Removal of SCons git submodule
- Removal of documentation which is stored in the sources and covers SCons
- Tweaks to the buildbot master to stop using SCons submodule
(this change requires deploying to the server)
- Tweaks to the install dependencies script to skip installing or mentioning
SCons building system
- Tweaks to various helper scripts to avoid mention of SCons folders/files
as well
Reviewers: mont29, dingto, dfelinto, lukastoenne, lukasstockner97, brecht, Severin, merwin, aligorith, psy-fi, campbellbarton, juicyfruit
Reviewed By: campbellbarton, juicyfruit
Differential Revision: https://developer.blender.org/D1680
Visual representation of fire was generated before simulation step took place. This caused fire to essentially lag one simulation step behind, even though all emission areas were up to date.
This was caused by a "hack" Daniel Genrich introduced in his moving obstacles commit in r46050. I suppose it was originally added to prevent issues with too fast moving obstacles, but now it ended up limiting maximum velocity of higher resolution simulations.
Here is an comparision of 184 resolution simulation (simulation area limited by adaptive domain):
https://www.miikah.org/blender/smoke_with_pressure_limit_hack.pnghttps://www.miikah.org/blender/smoke_without_pressure_limit_hack.png
I now reverted that hack until a better solution is found. Daniel, can you check this out? Pressure was limited to maximum of dt * dx (= dt / res) which doesn't make sense to limit pressure based on grid resolution. Maybe better to limit with a constant factor instead?
This caused high resolution smoke to always regenerate new tile when domain was reinitialized, slowing down especially adaptive domain simulations. Now noise tile is saved in Blender temp directory instead.
Note: this doesn't work yet for everything with latest stable bullet (2.81), need to look into why and likely apply some patches upstream.
However I managed to link blender by disabling some features, likely it can be made to work without too much trouble.
CMake had FFTW disabled by default, and when FFTW was not enabled it lead to
uninitialized memory usage. Now it falls back to wavelet if there is no FFTW,
and I've enabled it by default in CMake. If it's not found on Linux it will get
disabled automatically.
Documentation & Test blend files:
------------------
http://wiki.blender.org/index.php/User:MiikaH/GSoC-2012-Smoke-Simulator-Improvements
Credits:
------------------
Miika Hamalainen (MiikaH): Student / Main programmer
Daniel Genrich (Genscher): Mentor / Programmer of merged patches from Smoke2 branch
Google: For Google Summer of Code 2012
a) Another boundary fix. Resulted in smoke getting "sucked" back into the domain
b) Disabling substeps (internal thing). Fixes arbitrary explosions/instabilities.
Part of my Blender Smoke Development.
Detail: Smoke solver and Blender side of smoke now share the same cell length.
First reported by the Sintel artists long ago, again reported by MiikaH.
Part of my Smoke Development Project Phase III.
Sponsored by the Blender Development Fund.
http://www.blender.org/blenderorg/blender-foundation/development-fund/
Remarks:
The original code was not designed to support moving obstacles so I had to introduce some velocity constraints into the code to prevent smoke from exploding. If this causes problems with "fire" emulation, please let me know.
