Blender Git Loki

Fix for collision response, the impulse response was far too small.

Use the S matrix of the modifier CG algorithm for implementing collision
responses.

The S matrix together with the z Vector encodes the degrees of freedom
of a colliding hair point and the target velocity change. In a collision
the hair vertex is restricted in the normal direction (when moving
toward the collider) and the collision dynamics define target velocity.

Better contact point near-test for hair.

This simply uses the position above the triangle instead of the
intersection point of the vertex path. The other method was broken
anyway, but also has a problem catching all the contacts reliably. The
new method might have a few false positives but that is acceptable.

Revert "Terrible consequencer:"

This reverts commit 6b4fb627f754f71ef6cfba0f44cd14b4f6e17b5a.

Terrible consequencer:

Try testbuild for trim tool

Force refresh when trimming.

Trim operator, accessible through T key, also in Strip menu. It moves
the contents of the strip around.

Only tested with movie strips now, metastrips won't work. Also there
might be some lingering bugs. Sonetimes refresh is needed to get
contents showing up correctly.

Fixed for hair collision detection, old/new positions were swapped.

Reduced minimum for cloth solver substeps to 1.

This is not very useful for artists, but helps with debugging.

Removed own debug print.

Added a comment and use the new CG solver as the "official" version now.

constraint crash fix and breaking conditions fix (were evaluated incorrectly)

take minimum of island weight instead of average as threshold modifier

Fixed implementation of the Conjugate Gradient method for the cloth
solver that properly supports constraints with some degrees-of-freedom.

The previous solver implementation only used the S matrix (constraint
filter matrix) for pinning vertices, in which case all elements are
zero and the error doesn't show up. With partial constraints (useful for
collision contacts) the matrix has non-zero off-diagonal elements and
the algorithm easily diverges.

There are also initial steps for implementing collision prevention as
described in the Baraff/Witkin paper "Large Steps in Cloth Simulation"
(http://www.cs.cmu.edu/~baraff/papers/sig98.pdf).

cleanup related compile fixes

Cleanup for master, part 1, WARNING: Incompatible to older blends to to changes in DNA / loader

Hair collision: Use the S matrix for enforcing contact constraints.

This is a first test, the contacts are very explosive atm because they
basically pin hair vertices globally on collision, which leads to
stretching of the springs which is then suddenly released in the next
frame.

Minor corrections:

* Add some comments to better describe what some numbers mean
* Fix cuddliness and parent position of strips

Preparation for collision code fixing.

Instead of handling contact tests and collision response in the same
function in collision.c, first generate contact points and return them
as a list, then free at the end of the stepping function. This way the
contact response can be integrated into the conjugate gradient method
properly instead of using the hackish and unstable double evaluation
that is currently used.

Cleanup: added some comments to the members of Implicit_Data.