Зовнішньо – Exterior¶
Exterior forces are applied to the vertices (and nearly exclusively to the vertices) of soft body objects. This is done using Newton’s Laws of Physics:
- Якщо немає ніякої сили на вершині, то вона залишається або нерухомою або рухається з постійною швидкістю по прямій лінії.
- Прискорення вершини залежно від її маси та сили. Чим важче маса вершини, тим повільніше прискорення. Чим більша сила, тим більше прискорення.
- Для кожної дії є рівнозначна та протилежна протидія.
Ну, це робиться тільки у діапазоні точності обчислення, там завжди є трохи згасання для запобігання перевищення розрахування.
Приклад¶
Ми почнемо з дуже простого прикладу: стандартний куб.
- Для судження про ефект зовнішніх сил ви повинні спершу увімкнути ціль м’якого тіла Goal, щоб вершини не поверталися в їх оригінальну позицію.
- Start playback to run the simulation.
What happens? The cube moves in negative Z direction. Each of its eight vertices is affected by a global, constant force – the gravitation. Gravitation without friction is independent from the weight of an object, so each object you would use as a soft body here would fall with the same acceleration. The object does not deform, because every vertex moves with the same speed in the same direction.
Силові Поля – Force Fields¶
Soft body vertices interact with all the Force Fields applied (usually to particles) in the layer, such as wind, force fields, and what ever physics field effect is on a common layer.
Soft Body Field Weights¶
Орієнтир – Reference
| Panel: |
|---|
The Soft Body Field Weights panel allows you to control how much influence each type of external force field has on the soft body system.
- Effector Collection
- Limit effectors to a specified group. Only effectors in this group will have an effect on the current system.
- Gravity
- Control how much the Global Gravity has an effect on the system.
- All
- Scale all of the effector weights.
Аеродинаміка – Aerodynamics¶
Edges can be affected by wind as they move, and sail or flutter in a breeze. A simple aerodynamic model of a flag sailing in the wind.
Це особливе зовнішнє поле не застосовується до вершин, а до з’єднувальних ребер. Технічно, застосовується сила, перпендикулярна до ребра. Сила масштабується з проекцією відносно швидкості на ребрі (скалярний добуток). Зауважте, що ця сила є такою ж, як дме вітер або ніби ви тягнете ребро через повітря з такою ж швидкістю. Це означає, що ребро, що рухається у своєму напрямку, не відчуває жодної сили, а ребро, що рухається перпендикулярно до його напрямку, відчуває максимальну силу.
The angle and the relative speed between medium and edge is used to calculate the force on the edge. This force results that vertices with few connecting edges (front of a plane) fall faster than vertices with more connecting edges (middle of a plane). If all vertices have the same amount of edges in a direction they fall with equal speed.
The Aerodynamics settings are set in the Soft Body Edges panel.
Ціль – Goal¶
A «goal» is a shape that a soft body object tries to conform to. It acts like a pin on a chosen set of vertices, controlling how much of an effect soft body has on them.
Enabling Soft Body Goal tells Blender to use the position (or animated position) of a vertex in the simulation. Animating the vertices can be done in all the usual ways (F-curves, armatures, parents, lattices, etc.) before the soft body simulation is applied. The «goal» is the desired end position for vertices. How a soft body tries to achieve this goal can be defined using stiffness forces and damping.
See the Soft Body Goal settings for details.
Сила Цілі – Goal Strength¶
The Goal Strength defines how much motion from an animation system gets applied.
A Goal value of 1.0 means no soft body simulation, the object act like any regular animated object (i.e. the vertex is kept at its original position). When setting Goal to 0.0 (or no goal), the vertex is only influenced by physical laws according to soft body simulation.
By setting goal values between 0.0 and 1.0, you can blend between having the object affected only by the animation system, and having the object affected only by the soft body effect.
Goal also serves as a memory, to make sure soft objects don’t deform too much, ending up in the non-soft animated shape. Using the Vertex Group weight system, you can define a Goal weight per vertex. To make this look more natural, spring forces can be defined to control how far vertices can move from their original position.
Often Малювання Вагомостей – Weight Paint is used to adjust the weight comfortably. For non-mesh objects the Weight parameter of their vertices/control points is used instead; Specials menu W in Edit Mode or use the Transform panel in the Sidebar region. The weight of Hair particles can also be painted in Particle Edit Mode.
Technical Details¶
In the Soft Body world, vertices of meshes are treated as particles having a mass. Their movement is determined by the forces affecting them. Beside other forces the individual particles can interact with another along edges using a physical model which is very close to shock absorbers used in cars. The working parts are:
- A spring trying to keep the particles at a certain distance. How hard the spring tries to do that is controlled by the soft body parameter Stiffness.
- A damping element to calm the movement down. The resistance the element builds up against motion is controlled by the soft body parameter Damping.