the same, but big changes have happened both on the outside and on the inside.
New UI:
* The old parameters were quite true to the underlying algorithm, but were quite obscure
from a users point of view. Now there are only a few intuitive basic parameters that
define the basic fluid behavior.
** By default particle size is now used to determine the interaction radius, rest
density and spring rest lengths so that it's easy to get stable simulations by simply
emitting particles for a few frames and adjusting the particle size (easy when the
particle size is drawn) so that the fluid appears continuous (particles are touching
eachother).
** Stiffness - in reality most fluids are very incompressible, but this is a very hard
problem to solve with particle based fluid simulation so some compromises have to be
made. So the bigger the stiffness parameter is the less the fluid will compress under
stress, but the more substeps are needed for stable simulation.
** Viscosity - how much internal friction there is in the fluid. Large viscosities also
smooth out instabilities, so less viscous fluids again need more substeps to remain
stable.
** Buoancy - with high buoancy low pressure areas inside the fluid start to rise against
gravity, and high pressure areas start to come down.
* In addition to these basic parameters there are separate advanced parameters that can
either be tweaked relative to the basic parameters (or particle size) or defined
independently.
** Repulsion - the stiffness parameter tries to keep the fluid density constant, but this
can lead to small clumps of particles, so the repulsion keeps the particles better
separated.
** Stiff viscosity - the normal viscosity only applies when particles are moving closer to
eachother to allow free flowing fluids. Stiff viscosity also applies smoothing to
particles that are moving away from eachother.
** Interaction radius - by default this is 4 * particle size.
** Rest density - by default this is a density that the particles have when they're packed
densely next to eachother.
** Spring rest length - by default this is 2 * particle size.
* There are also new options for 3d view particle coloring in the display panel to show
particle velocity and acceleration. These make it easier to see what's happening in the
fluid simulations, but can of course be used with other particles as well.
* Viscoelastic springs have some new options too. The plasticity can now be set to much
higher values for instant deletion of springs as the elastic limit is exeeded. In addition
to that there is an option to only create springs for a certain number of frames when a
particle is born. These options give new possibilities for breaking viscoelastic fluids.
New in the code:
* Most of the fluids code is now thread safe, so when particle dynamics go threaded there
will be a nice speed boost to fluids as well.
* Fluids now use a bvh-tree instead of a kd-tree for the neighbor lookups. The bvh-tree
implementation makes the code quite a bit cleaner and should also give a slight speed
boost to the simulation too.
* Previously only force fields were calculated with the different integration methods, but
now the fluid calculations are also done using the selected integration method, so there
are again more choices in effecting simulation accuracy and stability. This change also
included a nice cleanup of the whole particle integration code.
As the internals are pretty stirred up old particle fluid simulations will probably not
work correctly straight away, but with some tweaking the same level of control is still
available by not using the "relative versions" of the advanced parameters (by default these
are not used when loading old files).
* Grid distribution isn't really suited for hair, so this is now disabled.
* Setting a jittered distribution with particles/face = 1 now creates particles on the center of faces.
* Quite a bit of cleanup of the whole particle distribution code.
* New option to distribute particles in a hexagonal grid.
* This is much more stable for fluids than normal grid distribution and looks quite nice otherwise too :)
* Also some small scale code cleanup of grid distribution code.
* Renamed the old split uv's animate option "time" to "age" and added a new option to change the used split frame by frame. These are good changes were suggested/implied by Hannu Hoffren over 3 years ago in his tutorial video! (oh my how time flies)
* Also cleaned up the billboard ui quite a bit. For example now the uv channels can be properly chosen from the existing channels.
* Greetings from farsthary: particle rotation is now taken into account for particle effector direction.
** This gives all kinds of new possibilities as he shows in his blog http://farsthary.wordpress.com/2011/02/08/vortex-particle-simple-tut/.
**The only modification I made to his patch was to use the actual rotated particle direction as the effector direction as this defaults to the particle velocity vector, so no actual new options are needed.
* I also added an "effector amount" setting for particle effectors so that only a part of the particles can be considered as effectors. This makes it possible to create simple "farsthary vortexes" with only one particle system.
* Also some tiny reorganization of the falloff min/max values for a nicer ui.
* Effecting particle properties with textures was possible in 2.49,
but not in 2.5 anymore.
* Now particles have their own textures (available in texture panel
for objects with particle systems), which are totally separate from
the material textures.
* Currently a basic set of particle properties is available for
texture control. Some others could still be added, but the whole
system is not intended as an "change anything with a texture" as
this kind of functionality will be provided with node particles in
the future much better.
* Combined with the previously added "particle texture coordinates"
this new functionality also solves the problem of animating particle
properties through the particle lifetime nicely.
* Currently the textures only use the intensity of the texture in
"multiply" blending mode, so in order for the textures to effect
a particle parameter there has to be a non-zero value defined for
the parameter in the particle settings. Other blend modes can be
added later if they're considered useful enough.
* There were a lot of settings in the particle panels that made no sense for simple hair and only cluttered up the ui.
* Now these settings are hidden by default unless "advanced" hair options are shown.
* Without advanced options the particle velocity controls are replaced by a simple "hair length" value, which actually corresponds to the grown hair length in blender units.
* Some hair effector options that are actually very useful were not shown in ui. These are now found in the "field weights" panel.
* Particles that aren't shown are now actually deleted (huge memory savings for flat objects).
* Grid distribution for flat objects is now done on the surface object surface without offset.
* Invert grid option wasn't in ui and it didn't work for non-volume grids.
* New parameter to randomize the grid point locations.
* Resolution soft/hard limits changed to even 50/250.
* Argh, particles tab was showing the whole "non applicable settings for fluid particles"-galore as the particle type "fluid" can't be checked from rna using the settings type value. Now the ui is a lot cleaner and only settings that actually effect the fluid particles are shown.
* Viscoelastic springs between the fluid particles can simulate all kinds
of viscous and elastic substances, such as jelly and honey. This is
achieved by creating springs dynamically between neighboring particles
and adjusting their rest length based on stretching/compression.
* This nearly completes the currently intended functionality for particle
fluids. The last missing thing is a surfacing extraction algorithm,
which is needed for a proper representation of a sph fluid.
* I also cleaned up and renamed some of the fluid parameters to make the
ui a bit easier to understand.
* One addition to the patch is an option to use "initial rest length" for
the springs, which uses the lengths between the particles at the time of
spring creation as the spring rest lengths instead of interaction radius/2.
This makes the fluid keep it's original shape better (good for very
viscoelastic materials), but can create large density differences inside
the fluid (not really physically correct for a fluid).
* Viscoelastic springs are stored in point cache as extra data.
* Renamed children to "simple" and "interpolated" as this is
easier to explain and more descriptive than "from particles"
and "from faces".
* Also shuffled the child ui around a bit to make it clearer.
* Child seed parameter allows to change the seed for children
independent of the main seed value.
* Long hair mode for interpolated children:
- Making even haircuts was impossible before as the child
strand lengths were even, but their root coordinates were
not similar in relation to the parent strands.
- The "long hair" option uses the tips of the parent strands
to calculate the child strand tips.
* Hair parting options:
- Hair parting can now be calculated dynamically on the fly
when in 2.49 there was a cumbersome way of using emitter mesh
seams to define parting lines.
- For long hair parting can be created by a tip distance/root
distance threshold. For example setting the minimum threshold
to 2.0 creates partings between children belonging to parents
with tip distance of three times the root distance
((1+2)*root distance).
- For short hair the parting thresholds are used as angles
between the root directions.
* New kink parameters:
- Kink flatness calculates kink into a shape that would have
been achieved with an actual curling iron.
- Kink amplitude clump determines how much the main clump value
effects the kink amplitude.
- The beginning of kink is now smoothed to make the hair look
more natural close to the roots.
* Some bugs fixed along the way too:
- Child parent's were not determined correctly in some cases.
- Children didn't always look correct in particle mode.
- Changing child parameters caused actual particles to be
recalculated.
* Also cleaned up some deprecated code.
All in all there should be no real changes to how old files look
(except perhaps a bit better!), but the new options should make
hair/fur creation a bit more enjoyable. I'll try to make a video
demonstrating the new stuff shortly.
* New option to "Regrow hair" for each frame.
* This was perhaps more a feature request, but there was a similar useful feature called "animated hair" in particles at some point.
* The previous behavior for hair growing was inconsistent to say the least, so this is a nice option to have.
only tags the ID and does the actual flush/update delayed, before the next
redraw. For objects the update was already delayed, just flushing wasn't
yet.
This should help performance in python and animation editors, by making
calls to RNA property update quicker. Still need to add calls in a few
places where this was previously avoided due to bad performance.
Changed some names when applying.
- render was use_render, changed to show_viewport so call it show_render
- texface shadow was use_shadow_face, changed to use_shadow_cast since this only affects casting.
- transp was alpha_mode, changed to blend_type since its similar to other overlay blending where this property name is used.
rather than in its own internally used emitting-face-coordinate-system
(which is how the data is stored in DNA - that data now exists in rna as
hairkey.location_hairspace)
Basically this makes the hair information that's in rna a lot more useful,
making it possible to export hair strands to external renderers for example.
* Increasing subframe count increases stability for SPH fluid and Newtonian particles
* Also small tweaks into physics ui panel to better fit new subframes value
* This commit also fixes the moving fluid emitter problem as described by Raul in the mailinglist
This patch add SPH (Smoothed Particle Hydrodynamics)fluid dynamics to the
blender particle system. SPH is an boundless Lagrangian interpolation
technique to solve the fluid motion equations.
From liquids to sand, goo and gases could be simulated using the particle
system.
It features internal viscosity, a double density relaxation that accounts
for surface tension effects, static internal springs for plastic fluids,
and buoyancy for gases.
---------------------------------------
This is a commit of the core fluid physics. Raul will work on proper
documentation soon and more features such as surface extraction from
the particle point cloud and increasing stability by sub-frame calculations
later.
