テンプレート:Release Notes/2.42/Physics/Fluid Simulation

fluid simulation

 Log:
 Sorry for the big commit, but I've been fixing many of these
 issues in parallel... So this commit contains: an update of
 the solver (e.g. moving objects), integration of blender IPOs,
 improved rendering (motion blur, smoothed normals) and a first particle
 test. In more detail:
 
 Solver update:
 - Moving objects using a relatively simple model, and not yet fully optimized - ok
   for box falling into water, water in a moving glass might cause trouble. Simulation
   times are influenced by overall no. of triangles of the mesh, scaling meshes up a lot
   might also cause slowdowns.
 - Additional obstacle settings: noslip (as before), free slip (move along wall freely)
   and part slip (mix of both).
 - Obstacle settings also added for domain boundaries now, the six walls of the domain are
   obstacles after all as well
 - Got rid of templates, should make compiling for e.g. macs more convenient,
   for linux there's not much difference. Finally got rid of parser (and some other code
   parts), the simulation now uses the internal API to transfer data.
 - Some unnecessary file were removed, the GUI now needs 3 settings buttons...
   This should still be changed (maybe by adding a new panel for domain objects).
 
 IPOs:
 - Animated params: viscosity, time and gravity for domains. In contrast
   to normal time IPO for Blender objects, the fluidsim one scales the time
   step size - so a constant 1 has no effect, values towards 0 slow it down,
   larger ones speed the simulation up (-> longer time steps, more compuations).
   The viscosity IPO is also only a factor for the selected viscosity (again, 1=no effect).
 - For objects that are enabled for fluidsim, a new IPO type shows up. Inflow
   objects can use the velocity channels to animate the inflow. Obstacles, in/outflow
   objects can be switched on (Active IPO>0) and off (<0) during the simulation.
 - Movement, rotation and scaling of those 3 types is exported from the normal
   Blender channels (Loc,dLoc,etc.).
 
 Particles:
 - This is still experimental, so it might be deactivated for a
   release... It should at some point be used to model smaller splashes,
   depending on the the realworld size and the particle generation
   settings particles are generated during simulation (stored in _particles_X.gz
   files).
 - These are loaded by enabling the particle field for an arbitrary object,
   which should be given a halo material. For each frame, similar to the mesh
   loading, the particle system them loads the simulated particle positions.
 - For rendering, I "abused" the part->rt field - I couldnt find any use
   for it in the code and it seems to work fine. The fluidsim particles
   store their size there.
 
 Rendering:
 - The fluidims particles use scaled sizes and alpha values to give a more varied
   appearance. In convertblender.c fluidsim particle systems use the p->rt field
   to scale up the size and down the alpha of "smaller particles". Setting the
   influence fields in the fluidims settings to 0 gives equally sized particles
   with same alpha everywhere. Higher values cause larger differences.
 - Smoothed normals: for unmodified fluid meshes (e.g. no subdivision) the normals
   computed by the solver are used. This is basically done by switching off the
   normal recalculation in convertblender.c (the function calc_fluidsimnormals
   handles other mesh inits instead of calc_vertexnormals).
   This could also be used to e.g. modify mesh normals in a modifier...
 - Another change is that fluidsim meshes load the velocities computed
   during the simulation for image based motion blur. This is inited in
   load_fluidsimspeedvectors for the vector pass (they're loaded during the
   normal load in DerivedMesh readBobjgz). Generation and loading can be switched
   off in the settings. Vector pass currently loads the fluidism meshes 3 times,
   so this should still be optimized.
 
 Examples:
 - smoothed normals versus normals from subdividing once:
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/v060227_1smoothnorms.png
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/v060227_2subdivnorms.png
 - fluidsim particles, size/alpha influence 0:
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/v060227_3particlesnorm.png
   size influence 1:
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/v060227_4particlessize.png
   size & alpha influence 1:
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/v060227_5particlesalpha.png
 - the standard drop with motion blur and particles:
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/elbeemupdate_t2new.mpg
   (here's how it looks without
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/elbeemupdate_t1old.mpg)
 - another inflow animation (moving, switched on/off) with a moving obstacle
   (and strong mblur :)
   http://www10.informatik.uni-erlangen.de/~sinithue/temp/elbeemupdate_t3ipos.mpg
 
 Things still to fix:
 - rotating & scaling domains causes wrong speed vectors
 - get rid of SDL code for threading, use pthreads as well?
 - update wiki documentation
 - cool effects for rendering would be photon maps for caustics,
   and motion blur for particles :)

fluids

 - New options for mesh voxelization: shell only (also
   works for non closed objects), volume ("normal"/old way of
   doing it), and a combination of both:
   http://www10.informatik.uni-erlangen.de/~sinithue/blender/voltcomp_sm.jpg
 - Finally included bjornmose MSVC6 fixes
 - Added support for animated meshes, e.g. meshes with
   parented skeletons. Is enabled for obstacles with a new button.
   A simple example with Bassam's mancandy can be found here:
   http://www10.informatik.uni-erlangen.de/~sinithue/blender/fluid2_mancandy.mpg
   http://www10.informatik.uni-erlangen.de/~sinithue/blender/fluid2_mancandy.blend
   (Warning - keep meshes as simple as possible, e.g. turn off subsurf
   for baking. Export probably shoulb be further optimized.)
 - Changed handling of no/free/part slip obstacles, see:
   http://www10.informatik.uni-erlangen.de/~sinithue/blender/bndtcomp_sm.jpg
 - Removed surface particle option for upcoming release,
   needs more testing & tweaking
 - Added tracer particles instead (swimming along in the fluid)
 - Updated wiki (description of IPOs still missing).