This is BAD code, but the particle kinking does not make it easy to
write a non-local modifier that requires neighboring positions,
curvature, etc. The feature is needed for Gooseberry.
This adds another level of clumping on child hairs. When enabled, child
hairs chose a secondary clumping target using a Voronoi pattern. This
adds visual detail on a smaller scale, which is useful particularly when
the number of parents is relatively small.
Natural fibres behave in a similar way when they become sticky and
intertwined. Hairs close to each other form a first twisted strand, then
combine into larger strands. Similar features can be found in ropes:
http://en.wikipedia.org/wiki/Hair_twistshttp://en.wikipedia.org/wiki/Rope
Conflicts:
source/blender/blenloader/intern/versioning_270.c
Scope update is very slow for high resolutions, and currently blocks
the UI thread(!). This is especially terrible in paint modes, where
each stroke causes a scope update and unacceptable freezing.
The scopes update method tries to avoid this somewhat by skipping if the
toolbar is disabled, but this doesn't help when painting where brush
tools etc. are frequently needed. It's also a bad-level poll, with the
core system accessing a UI element.
Eventually scope updates should become a low-priority background job,
as well as becoming threaded. Until then this polling provides a usable
workaround to the most outrageous cases.
This is an alternative method to the current fixed function with a
clump factor and "shape" parameter. This function is quite limited and
does not give the desired result in many cases (e.g. long, parallel
rasta strands are problematic). So rather than trying to add more
parameters there is now a fully user-defined optional curve for setting
the tapering shape.
This contains a few pieces of code for a future "modifier" system that
would allow more flexible combination of effects. Eventually a node
system is the way to go, but the current code makes that impossible.
to prevent double-freeing/invalid mem access.
This can happen with the "virtual parents" feature, which generates both
parent and child paths. Each task free function also freed the shared
context, leading to double freeing.
Cloth data is used both for hair and actual cloth, which makes things
really difficult. The face number was used for distinguishing the two
types (no faces == hair mesh), but the extra hair data necessary for
hair sim is generated by particles and not available for edge-only cloth
meshes. This really needs to be sanitized ...
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
approach does not work very well.
Using a cross section estimate still causes large oscillations due to
varying hair force based on angles. It also requires a sensible hair
thickness value (particle radius) which is difficult to control and
visualize at this point.
The new model is based purely on per-vertex forces, which seems to be
much more stable. It's also somewhat justified by the fact that each
hair vertex represents a certain mass.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
The previous calculation was modulated with the angle between the wind
direction and the segments, which leads to very oscillating behavior.
Now the formula includes an estimate for the geometric cross section
of a hair segment based on the incident angle and the hair thickness
(currently just the particle size). This gives a more stable behavior
and more realistic response to wind.
Conflicts:
source/blender/blenkernel/intern/particle_system.c
source/blender/physics/intern/BPH_mass_spring.cpp
This module will contain mirrored functions for calculating and applying
weights for points on a mesh. This includes barycentric and UV weighting
and possibly more advanced global weighting such as harmonic weights.
The naming should follow this scheme:
<type>_{2d,3d}_{calc,apply}
e.g.
poly_2d_calc
poly_2d_apply
uv_3d_calc
...
Reviewers: campbellbarton
Differential Revision: https://developer.blender.org/D939
A stupid hack is needed here, changing the way the factor is applied to
angular bending springs. In cloth sim the bending factor of individual
springs is applied as a mix value between the bending stiffness and a
max value, but this max value isn't even used in hair sim so that
approach becomes useless.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
This helps to create some variation in a hair system, which can
otherwise become very uniform and boring. It's yet another confusing
setting in a system that should have been nodified, but only option for
now (broken windows ...)
Conflicts:
source/blender/blenkernel/intern/particle_system.c
source/blender/physics/intern/BPH_mass_spring.cpp
framing method instead of the Frenet frame.
The Frenet frame is very succeptible to sudden twists along straight
sections of a curve where the second derivative (curvature) becomes 0.
to support multiple hash identifiers.
Using explicit hashing functions for every sim debug call defeats the
purpose of having a quick feedback system. Now this can be done simply
by passing an arbitrary number of hash inputs (integers) at the end of
the function calls, which are then combined by a system of variadic
macros (based on the ELEM feature). Up to 8 identifiers are supported
currently, but more could be added easily if needed.
Conflicts:
source/blender/blenkernel/intern/particle_system.c
source/blender/physics/intern/BPH_mass_spring.cpp
solver input and output.
This uses the central difference method (instead of combined forward/
backward difference), which makes it easier to correctly account for
grid borders.
samples.
This is just an intermediate method to make sure the density is valid.
Eventually the closest-point method should be used, but for testing
the poisson solver this is easier to debug.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
This allows setting a target density which the fluid simulation will
take into account as an additional term in the pressure Poisson
equation. Based on two papers
"Detail Preserving Continuum Simulation of Straight Hair" (McAdams et al. 2009)
and
"Two-way Coupled SPH and Particle Level Set Fluid Simulation" (Losasso et al. 2008)
Currently the target pressure is specified directly, but it will be
a lot more convenient to define this in terms of a geometric value such
as "number of hairs per area" (combined with hair "thickness").
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
on the grid.
This uses the Eigen conjugate-gradient solver to solve the implicit
Poisson equation for the pressure Laplacian:
div(grad(p)) = div(v)
As described in "Detail Preserving Continuum Simulation of Straight Hair"
(McAdams, Selle, 2009).
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
This is a bit more awkward for artists to use, but necessary for
a stable solution of the hair continuum calculation. The grid size is
defined by the user, the extent of the grid is then calculated based on
the hair geometry. A hard upper limit prevents bad memory allocation
in case too small values are entered.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
This is an artifact of earlier attempts to implement velocity smoothing,
but doesn't work anyway.
Conflicts:
source/blender/physics/intern/BPH_mass_spring.cpp
