Softbody was still using a flag to determine if it should use the final or
deform derivedmesh, but this wans't exposed in the UI. Others systems use the
collision modifier, now softbody uses it also to get vertices and faces, but
with own collision code.
* 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.
* Not strictly necessary right now, but better for future.
* Struct data (only boids at the moment) is now written as structs (with dna) so they work between 64 and 32 bit machines too.
* I've getting bad feelings about the point cache index_array for a while (cause for this bug too), so from now on memory cache uses a simple binary search directly on the index data to handle queries to specific data points.
* This is a bit slower than just checking from a dedicated array, but it's much less error prone, uses less memory and makes the code more readable too, so it's not a tough choice.
* Massive reorganization of pointcache code, things are now cleaner than ever.
* For all but smoke the cache is first written to memory when using disk cache and after that written to disk in one operation. This allows less disk operations and the possibility to compress the data before writing it to disk.
* Previously only smoke cache could be compressed, now the same options exist for other physics types too (when using disk cache). For now the default compression option is still "no compression", but if there aren't any problems this can be set to "light compression" as it's actually faster than no compression in most cases since there's less data to write to the disk. Based on quick tests heavy compression can reduce the file size down to 1/3rd of the original size, but is really slow compared to other options, so it should be used only if file size is critical!
* The pointcache code wasn't really 64bit compatible (for disk cache) until now, so this update should fix some crashes on 64bit builds too. Now all integer data that's saved to disk uses 32 bit unsigned integers, so simulations done on 64bit should load fine on 32bit machines and vice versa. (Important disk cache simulations made on 64bit builds should be converted to memory cache in a revision before this commit).
* There are also the beginnings of extradata handling code in pointcache in anticipation of adding the dynamic springs for particle fluids (the springs need to be stored as extradata into point cache).
* Particles were being read from the cache with a slightly wrong framerate. In most cases this probably wasn't noticeable, but none the less the code is now correct in every way.
* Small other fixes here and there & some cosmetic changes to cache panel, but over all there should be no functional changes other than the new disk cache compression options.
* This whole re-organization also seems to fix bug #25436 and hopefully shouldn't introduce any new ones!
* Separate caches were causing quite a lot of problems both in principle and practice.
* For example it doesn't really make sense to have different frame ranges for normal and high resolution smoke, but this was fully possible before.
* Also to fully bake the smoke you had to do a "Bake All Dynamics", which completely defeats the whole point of the feature!
* As a result of this change the smoke cache usage is much much simpler and less error prone.
* This is quite a big change, but hopefully there should be less rather than more problems as a result :)
Some other related changes:
* Changing the cache name now works for disk caches properly too, it now just renames the cache files so should be faster too!
* Smoke is now always forced to disk cache with step 1 on file load as there were some strange cases where smoke was trying to use memory cache.
* Disabled smoke debug prints from console.
* Disabled changing smoke parameters when smoke is baked.
Note to users: The unfortunate side effect of this is that old high resolution simulations have to be baked again, but in return you get much better and more logical functionality. Sorry none the less!
* The existence of cached frames was checked each frame causing hundreds of disk operations per frame update.
* Pointcache now keeps an updated array of the cached frames for fast "frame exists in cache" queries.
* This fix also speeds up some other pointcache operations nicely.
sb->lcom : Center Of Mass .. might be used to create loc IPO
sb_>lrot : is a matrix[3] esitmates the roatation in world coordinates .. might be used to create rot IPO
sb_>lscale : is a matrix[3] esitmates the scaling in world coordinates .. might be used to create scale IPO
(no python for that yet .. but may be matt has mercy on me )
can be cropped direclty in soft body module by function
static void SB_estimate_transform(Object *ob,float lloc[3],float lrot[3][3],float lscale[3][3])
The targets lloc,lrot,lscale should work to be NULL, just in case you don't need it.
However i'd prefer if they were accessed via properties
which should be calculated automagically if
sb->solverflags & SBSO_ESTIMATEIPO
is set, like they do in draw_sb_motion(..) in drawobject.c
added static void draw_sb_motion(Scene *scene, Object *ob) to drawobject.c
for debuggering (had a hard time with destructive matrix operations )
if it causes any trouble with your build on any OS make sure to comment that away.
softbody.c and DNA should compile fine in any case.
The goodies:
* Curves can be used as normal dynamic effectors too with
the new "curve" field shape.
* Group visualization has optional duplication counts for
each object in the specified group.
* Object & group visualizations, which are done without
taking the dupliobject's global position into account
(unless the whole group is used). This is much nicer than
the previous behavior, but I added a "Use Global Location"
option for those who want to use it the old way.
* The active particle system's particles are now drawn a
with theme coloured outline instead of pure white.
* Added object aligned velocity factors (buttons categorized
and re-organized too).
Bug fixes:
* Absorption didn't work as the ui toggle button was forgotten.
* Some other force field ui tweaks.
* Crash after adding children and changing trails count.
* Display types "cross" and "axis" crashed.
* Particles weren't drawn with correct coloring.
* Billboards didn't update properly in viewport to camera
location changes.
* Particle rotation wasn't recreated correctly from point cache.
* Changing particles amount crashed sometimes.
* Some files with child hair crashed on loading.
* Compiler warning fixes.
* Adding boids crashed on frame 1;
* Unified scene wide gravity (currently in scene buttons)
instead of each simulation having it's own gravity.
* Weight parameters for all effectors and an effector group
setting.
* Every effector can use noise.
* Most effectors have "shapes" point, plane, surface, every point.
- "Point" is most like the old effectors and uses the
effector location as the effector point.
- "Plane" uses the closest point on effectors local xy-plane
as the effector point.
- "Surface" uses the closest point on an effector object's
surface as the effector point.
- "Every Point" uses every point in a mesh effector object
as an effector point.
- The falloff is calculated from this point, so for example
with "surface" shape and "use only negative z axis" it's
possible to apply force only "inside" the effector object.
* Spherical effector is now renamed as "force" as it's no longer
just spherical.
* New effector parameter "flow", which makes the effector act as
surrounding air velocity, so the resulting force is
proportional to the velocity difference of the point and "air
velocity". For example a wind field with flow=1.0 results in
proper non-accelerating wind.
* New effector fields "turbulence", which creates nice random
flow paths, and "drag", which slows the points down.
* Much improved vortex field.
* Effectors can now effect particle rotation as well as location.
* Use full, or only positive/negative z-axis to apply force
(note. the z-axis is the surface normal in the case of
effector shape "surface")
* New "force field" submenu in add menu, which adds an empty
with the chosen effector (curve object for corve guides).
* Other dynamics should be quite easy to add to the effector
system too if wanted.
* "Unified" doesn't mean that force fields give the exact same results for
particles, softbody & cloth, since their final effect depends on many external
factors, like for example the surface area of the effected faces.
Code changes
* Subversion bump for correct handling of global gravity.
* Separate ui py file for common dynamics stuff.
* Particle settings updating is flushed with it's id through
DAG_id_flush_update(..).
Known issues
* Curve guides don't yet have all ui buttons in place, but they
should work none the less.
* Hair dynamics don't yet respect force fields.
Other changes
* Particle emission defaults now to frames 1-200 with life of 50
frames to fill the whole default timeline.
* Many particles drawing related crashes fixed.
* Sometimes particles didn't update on first frame properly.
* Hair with object/group visualization didn't work properly.
* Memory leaks with PointCacheID lists (Genscher, remember to
free pidlists after use :).
% sign for percentage assuming it is between 0-100, while factor is
for values 0-1.
Move collision setting absorption from modifier to collision settings,
was inconsistent to have it there as the only one, and made it have
range 0.0-1.0 instead of 0-100.
- Hair dynamics have their own panel in particle settings with the settings from cloth panel that apply to hair.
- Basic internal friction force to quickly emulate self collisions and volume preservation. (Still very early code, but gives some idea of what's possible).
- Softbody simulation is no longer used for hair.
* Old files with sb dynamics should just load the hair without dynamics so new dynamics can be applied.
* Invasion of particles exceptions in sb code is finally over.
- Collisions with other objects are disabled for now and will be worked out in the future.
Other changes/fixes:
- Particle mode editing flag wasn't saved properly.
- Some old files with edited hair didn't load correctly.
- Disabled delete & specials menu in particle mode for non-hair editing.
- Fixed yet one more cloth & softbody pointcache update issue.
- Disconnect/connect hair now uses only the deformed mesh so it works correctly also for subsurfed emitters.
- Hair editing now updates correctly with a moving emitter.
- Baked point caches for particles, cloth and softbody can now be edited in particle mode.
* This overwrites the old cloth/sb cache editmode editing.
* The type of editable system is chosen from a menu.
* For particles the current particle system and it's current cache are used.
- Currently this only works for caches that are in memory, but some automatic conversion from disk to memory and back can be implemented later.
- All tools from hair editing can't be applied to point caches and are hidden in the tool panel and specials menu. Some functionality like subdividing paths can be later implemented in a slightly different way from how it works for hair.
- Code is not yet optimized for speed, so editing might be slow sometimes.
Known issues:
- Cloth doesn't update properly while in particle mode, due to the way cloth modifier currently works. Daniel can you check on this?
- As "particle mode" is not only for particles any more some other name would be in place?
- Better icons are needed for the path, point, and tip-modes as the current icons from mesh edit mode are quite misleading.
- Direct editing of point velocities is not yet implemented, but will be in the future.
Other changes:
- Hair editing doesn't require a "make editable" button press any more.
- Multiple caches in single particle system disables changing emission properties.
- Unified ui code for all point cache panels.
* Defined in buttons_particle.py and imported for cloth, smoke & softbody.
- Proper disabling of properties in ui after baking point caches. (Daniel could you please make needed disable code for smoke panels as their functionality is not familiar to me.)
- Hair weight brush has been removed. Once hair dynamics is re-implemented I'll code a more useable alternative to the functionality.
Bug fixes:
- Unlinking particle settings crashed.
- Deleting the active object with particles in the scene crashed.
- Softbody didn't write point caches correctly on save.
- HEADER (beginning of each file)
* general header:
+ 8 char: "BPHYSICS"
+ 1 int: simulation type (same as PTCacheID->type)
* custom header (same for sb, particles and cloth, but can be different for new dynamics)
+ 1 int: totpoint (number of points)
+ 1 int: data_types (bit flags for what the stored data is)
- DATA (directly after header)
*totpoint times the data as specified in data_types flags
- simulation type
soft body = 0, particles = 1, cloth = 2
- data types (more can be added easily when needed)
data flag contains
----------------------------------------
index (1<<0) 1 int (index of current point)
location (1<<1) 3 float
velocity (1<<2) 3 float
rotation (1<<3) 4 float (quaternion)
avelocity (1<<4) 3 float (used for particles)
xconst (1<<4) 3 float (used for cloth)
size (1<<5) 1 float
times (1<<6) 3 float (birth, die & lifetime of particle)
boids (1<<7) 1 BoidData
Notes:
- Every frame is not nescessary since data is interpolated for the inbetween frames.
- For now every point is needed for every cached frame, the "index" data type is reserved for future usage.
- For loading external particle caches only "location" data is necessary, other needed values are determined from the given data.
- Non-dynamic data should be written into an info file if external usage is desired.
* Info file is named as normal cache files, but with frame number 0;
* "Non-dynamic" means data such as particle times.
* Written automatically when baking to disk so basically a library of particle simulations should be possible.
- Old disk cache format is supported for reading, so pre 2.5 files shouldn't break. However old style memory cache (added during 2.5 development) is not supported. To keep memory cached simulations convert the cache to disk cache before svn update and save the blend.
- External sb and cloth caches should be perfectly possible, but due to lack of testing these are not yet enabled in ui.
Other changes:
- Multiple point caches per dynamics system.
* In the future these will hopefully be nla editable etc, but for now things are simple and the current (selected) point cache is used.
* Changing the amount of cached points (for example particle count) is allowed, but might not give correct results if multiple caches are present.
- Generalization of point cache baking etc operator & rna code.
- Comb brushing particle hair didn't work smoothly.
missing commits from peter 20942, 21165, 21170, 21174, 21597
these files still need manual merging
source/blender/makesdna/DNA_sequence_types.h
source/blender/src/sequence.c
source/blender/src/seqeffects.c
source/blender/src/editseq.c
source/blender/include/BSE_sequence.h
Particle point cache can now be loaded from external files.
- Activated by "external" checkbox in cache panel and giving proper folder path and file name identifier.
- External cache panel has controls for particle emission start, end, lifetime and random lifetime. These should be set according to the external data for correct playback.
- External files should be named "identifier_frame_index.bphys" or "identifier_frame.bphys" where:
* "identifier" is a freely choseable name.
* "frame" is the cached frame number.
** Six digits padded with zeros!, for example "000024".
* "index" can be used to tell caches with the same identifier apart.
** Two digits starting from zero.
** The index and the underscore before are optional. If no index is present the index number in ui should be set to -1.
- Cache file format is pure floating point numbers (in binary, not text!) with each particle's data one after the other with the following data members:
* 3 floats: particle's location vector
* 3 floats: particle's velocity vector (per second)
* 4 floats: particle's rotation quaternion
* 3 floats: particle's angular velocity vector (per second)
* 1 float: frame of the actual data (this can be non-integer for particles that are born or die between two integer frames, but otherwise should be the same as the "frame" in the file name)
- Cache files don't have to exist for each frame.
* Frames without actual data are interpolated from surrounding frames that have data (extrapolation is not supported).
- Cache file formats with extended (or reduced even) data members are in future plans for easier usage.
- Current code only does particles, don't yet know if it's applicable to cloth or sb.
- Known issue: endianness can't yet be handled in any way.
Other changes:
New hard limits for many particle parameters. Some examples:
- Maximum amount of particles: 10M particles :) And before you all go and crash your Blender trying this out remember that this limit is only for those freaks who really have the machine power to handle it. 10M particles alone take around 2.2 Gb of memory / disk space in saved file and each cached frame takes around 0.5 Gb of memory / disk space depending on cache mode.
* Known issue: To actually use this many particles they most likely need to be allocated in parts as taking hold of a 2.2Gb chunk of memory at once is probably not ok with any operating system.
- Maximum amount of children: 100k children/particle (1T childparticles here we come :D)
- Kink frequency: -100k to 100k half-rotations (really strange the previous limit was only from zero upwards)
- Path draw steps: 10 (power of 2 remember)
- Path render steps: 20 (power of 2 also!! If over 1M segments doesn't get you smooth paths then I think nothing will!)
Too many new features to list! But here are the biggies:
- Boids can move on air and/or land, or climb a goal object.
- Proper interaction with collision objects.
* Closest collision object in negative z direction is considered as ground.
* Other collision objects are obstacles and boids collide with them.
- Boid behavior rules are now added to a dynamic list.
* Many new rules and many still not implemented.
* Different rule evaluation modes (fuzzy, random, average).
- Only particle systems defined by per system "boid relations" are considered for simulation of that system.
* This is in addition to the boids own system of course.
* Relations define other systems as "neutral", "friend" or "enemy".
- All effectors now effect boid physics, not boid brains.
* This allows forcing boids somewhere.
* Exception to this is new "boid" effector, which defines boid predators (positive strength) and goals (negative strength).
Known issue:
- Boid health isn't yet stored in pointcache so simulations with "fight" rule are not be read from cache properly.
- Object/Group visualization object's animation is not played in "particle time". This is definately the wanted behavior, but isn't possible with the current state of dupliobject code.
Other new features:
- Particle systems can now be named separately from particle settings.
* Default name for particle settings is now "ParticleSettings" instead of "PSys"
- Per particle system list of particle effector weights.
* Enables different effection strengths for particles from different particle systems with without messing around with effector group setting.
Other code changes:
- KDTree now supports range search as it's needed for new boids.
- "Keyed particle targets" renamed as general "particle targets", as they're needed for boids too. (this might break some files saved with new keyed particles)
Bug fixes:
- Object & group visualizations didn't work.
- Interpolating pointcache didn't do rotation.
All kinds of changes to get it ready for UI layouts. This means RNA
and operators should be working correct, but most buttons are still
not actually there yet.
* Added near empty soft body, fluid, field and collision panels,
tweaks to cloth panels.
* Fluid bake works, but without escape or showing any progress.
* Fluid/Softbody/Cloth/Collision can now be both added as modifiers
or in the physics panels.
* Missing: fields & soft body for particles.
* Missing: proper updating softbodies, guess this code still needs
updates after pointcache refactor?
* Based on what happens during simulation the cache is marked (also in cache panel, this could possibly be extended to 3d view as well) as:
- exact (not marked)
- outdated (simulation is not done completely with current settings)
- non-exact (frames were skipped during simulation)
* The parameter "cache step" effects the number of frames between saved cache frames.
- This can save a lot of memory (or disk space) if absolutely frame accurate simulation is not required.
- Speeds up the "quick caching" very much.
- Frames between cached frames are interpolated from the cached frames.
- Current default value of 10 frames works nicely with up/down-arrows (skip 10 frames forwards/backwards on timeline), but can be changed if wanted.
* The caching can work in normal or "quick" mode:
[Normal cache]
- Basic: Calculate what even happens (settings change, big frame steps etc.) and cache results, if possible try to use "cache step" when saving cache frames.
- Becomes non-exact: After larger than 1 frame steps.
- Becomes outdated: After any change effecting the simulation other than frame steps.
- Pros/cons: Freedom of doing anything and playing with particles, but exact results have to calculated from the beginning.
[Quick cache]
- Basic: Calculate simulation up to current frame automatically on changes with cache step sized jumps in simulation. With multiple "quick cached" simulations the smallest cache step is used.
- Becomes non-exact: Always from frame 1 (unless cache step = 1).
- Becomes outdated: Never.
- Pros/cons: Not very accurate, but super fast!
- Todo: Transform of any animated (non-autokeyed) object is locked! Probably needs some tinkering with anim sys overrides.
* The simulation can be run forwards or backwards even if it's cache is outdated or non-exact, the following rules apply in these situations:
- step forwards (to unknown) -> simulate from last exact frame, store result
- step backwards (to known) -> result is interpolated from existing frames, store result, clear cache forwards if current frame is after last exact frame
* "Calculate to current frame" runs the simulation from start to current frame with a frame steps of 1.
- Baking does the same, but runs the simulation all the way to the end of simulation.
- Rendering does this automatically if the simulation is outdated of non-exact, so all rendered simulations will always be updated and exact.
* Every cache panel also holds buttons to "Bake all dynamics", "Free all dynamics" and "Update all dynamics to current frame".
* Cloth simulation supports the new cache too.
* Particles support larger than 1 frame changes, bigger frame changes can result in inaccurate results, but it's super fast and you get a nice feeling of how the particles behave!
* "Cache to current frame" button calculates the exact result of particles at current frame.
* Current state of cache can be protected by making it a bake.
* Cache is now in memory by default, disk cache is an option.
* Only "viewport %" number of particles are calculated and cached in viewport, baking and rendering calculate all particles.
* Info on cached frames and memory usage given in ui.
* Support for exact "autocaching" of changes and large frame changes(disabled for now until exact place in event system is decided)
* "Continue physics" is probably deprecated after this and should be removed once sb & cloth use the new cache code.
Todo:
* Make softbody & cloth use the new cache things.
Other changes:
* Some cleanup of particle buttons.
svn merge https://svn.blender.org/svnroot/bf-blender/trunk/blender -r19820:HEAD
Notes:
* Game and sequencer RNA, and sequencer header are now out of date
a bit after changes in trunk.
* I didn't know how to port these bugfixes, most likely they are
not needed anymore.
* Fix "duplicate strip" always increase the user count for ipo.
* IPO pinning on sequencer strips was lost during Undo.
- Most mesh particle effectors can now have their effection point taken per particle as the nearest point on the mesh surface.
- This is activated with the "surface" button in the effector field panel.
- Activating the option adds a "surface" entry to the modifier stack where the state of the mesh is read from.
For an example of usage see http://www.youtube.com/watch?v=3XkO1EAmJks.
add -nojoystick commandline option: it takes 5 seconds everytime to start the game engine, while there IS no joystick.
In other words: blender -noaudio -nojoystick improves workflow turnaround times for P - ESC from 7 seconds to 1 second!
Improved Bullet soft body advanced options, still work-in-progress. Make sure to create game Bullet soft bodies from scratch, it is not compatible with last weeks builds.
- For newtonian particles a "self effect" button in particle extras makes the particles be effected by themselves if a particle effector is defined for this system, currently this is a brute force method so things start getting slow with more than ~100 particles, but this will hopefully change in the future.
- Two new effector types: charge and a Lennard-Jones potential based force (inter-molecular forces for example).
-Charge is similar to spherical field except it changes behavior (attract/repulse) based on the effected particles charge field (negative/positive) like real particles with a charge.
-The Lennard-Jones field is a very short range force with a behavior determined by the sizes of the effector and effected particle. At a distance smaller than the combined sizes the field is very repulsive and after that distance it's attractive. It tries to keep the particles at an equilibrium distance from each other. Particles need to be at a close proximity to each other to be effected by this field at all.
- Particle systems can now have two effector fields (two slots in the fields panel). This allows to create particles which for example have both a charge and a Lennard-Jones potential.
=======================
Caching and Baking:
- The point cache is now cleared on DAG_object_flush_update(), and not cleared for time dependency graph updates.
- There is now a Bake button instead of Protect. Also cache start and end frames were added to softbody and particles.
- The cloth autoprotect feature was removed.
- The Ctrl+B menu now also bakes cloth and particles next to softbody and fluids. Additionally there are now frree bake and free cache menu entries.
- The point cache api has been changed. There is now a PTCacheID struct for each point cache type that can be filled and then used to call the point cache functions.
- PointCache struct was added to DNA and is automatically allocated for each physics type.
- Soft body now supports Bake Editing just like cloth.
- Tried to make the systems deal consistently with time ipo's and offsets. Still not sure it all works correct, but too complicated to solve completely now.
Library Linking:
- Added some more warnings to prevent editing settings on library linked objects.
- Linked objects now read from the cache located next to the original library file, and never write to it. This restores old behavior for softbodies. For local simulation the mesh and not the object should be linked.
- Dupligroups and proxies can't create local point caches at the moment, how to implement that I'm not sure. We probably need a proxy point cache for that to work (ugh).
Physics UI:
- Renamed deflection panel to collision for consistency and reorganized the buttons. Also removed some softbody collision buttons from the softbody panel that were duplicated in this panel for cloth.
- Tweaked field panel buttons to not jump around when changing options.
- Tabbing e.g. Soft Body Collision into the Soft Body panel, it now only shows Collision to make the panel names readable.
- I tried to make enabled/disabling physics more consistent, since all three system did things different. Now the two modifier buttons to enable the modifier for the viewport and rendering are also duplicated in the physics panels. Toggling the Soft Body and Cloth buttons now both remove their modifiers.
- Fixed modifier error drawing glitch.
Particles:
- Particles are now recalculated more often than before. Previously it did partial updates based on the changes, but that doesn't work well with DAG_object_flush_update() ..
- Fixed memory leak loading keyed particle system. Now keys are not written to file anymore but always created after loading.
- Make particle threads work with autothreads.
Continue Physics:
- The timeline play now has a Continue Physics option in the playback menu, which keeps the simulations going without writing them to the cache.
- This doesn't always work that well, some changes are not immediately updated, but this can be improved later. Still it's fun to get a feel for the physics.
Todo:
- Point cache can get out of sync with and undo and changing a file without saving it.
- Change the point cache file format to store a version (so old point cache files can be either converted or at least ignored), and to do correct endian conversion.
- Menu item and/or buttons for Ctrl+B.
- A system("rm ..") was changed to remove() since the former is very slow for clearing point caches. These system() calls were already giving trouble in a bug in the tracker, but really most use of this system("") should be changed and tested.
- The Soft Body Collision and Clot Collision panel titles don't mention there's point cache settings there too, doing that makes them unreadable with the default panel setup.. but may need to make the names longer anyway.
Without this, animating grass would either look like seaweed (with low freq texture)
Or the grass would wrinkle up and get kinks (high freq texture)
This lets you use a high frequency texture while having straight grass.
a glance to view is the "STU PID semi implicit euler"
most of the work to implement a semi implicit euler was done ..
now i am dealing with the tradeoffs between 'calculation time' which is quite expensive .. inverting a 0(n*n) sparse matrix /* once agian thanks to brecht for his work on making sparse matrices LU decomposition and evaluating inverses that easy*/ putting it into and cropping works pretty nice .. argh off topic again
...
while i spent a little time on reading recent papers i found :
1. control on springs needs to be split in pushing and pulling /* fabric pushes easy but pulls hard */
2. diagonals on 4-gons (in the current SB model) can be seen as shear .. thus need a contol to modify .. this commit wil add it
3. 2 nd order springs /*aka rigidity */ can focus on bending .. thus renaming 'em
i have no idea how i would provide backward compatiblity, but the spots i marked in code :)
