|Описание||Как имитировать притяжение объектов друг к другу?|
|Область знаний||Биология, Информатика, Физика|
|Область использования (ISTE)||Computational Thinker|
|Близкие рецепту понятия||Преследовать другого агента|
|Среды и средства для приготовления рецепта:||Scratch, Snap!, StarLogo Nova|
In Object Attraction two or more objects are attracted to each other; or are pulling on each other. This can also be referred to as gravity.
Elliptical Orbit Method
One way to make one object attracted to another object is to make a sprite "Orbit" around the other object. This method is always 100% accurate and will automatically move when the object that it is being rotated about moves. Here is a script that creates an elliptical orbit:
when green flag clicked set [semi-major-axis v] to  //longest radius set [semi-minor-axis v] to  //shortest radius set [t v] to  // current angle set [inclination v] to  //inclination of the ellipse forever repeat (360) set [x v] to ((([cos v] of (t)) * (semi-major-axis)) + ([x position v] of [Sprite3 v])) set [y v] to ((([sin v] of (t)) * (semi-minor-axis)) + ([y position v] of [Sprite3 v])) set x to (((x) * ([cos v] of (inclination))) - ((y) * ([sin v] of (inclination))))//tilt 'inclination' degrees. Trigonometric additive theorey set y to (((x) * ([sin v] of (inclination))) + ((y) * ([cos v] of (inclination)))) change [t v] by (5) end end
Remember that this script goes in the object that is being rotated.
One example of the elliptical orbit method can be found here.
Another method is to have a sprite change its velocity automatically based on its position. This method is very inaccurate however it can be very useful if your creating a game where you have to avoid multiple sprites. The Following scripts will be placed into the item that is "following" another sprite:
when green flag clicked set [y speed v] to  set [x speed v] to  forever if <([x position v] of [Sprite2 v]) < (x position)> then change [x speed v] by (-0.1) end if <([x position v] of [Sprite2 v]) > (x position)> then change [x speed v] by (0.1) end if <([y position v] of [Sprite2 v]) < (y position)> then change [y speed v] by (-0.1) end if <([y position v] of [Sprite2 v]) > (y position)> then change [y speed v] by (0.1) end end when green flag clicked forever go to x: ((x position) + (x speed)) y: ((y position) + (y speed)) end
- Пример проекта с притяжением объектов
- Simulating Gravity
Direct Movement Method
This method although far more basic than the previous methods, can be very useful in certain situations. This method is very accurate and will move automatically with the sprite. Here is an example script that would be place in the sprite that is "following" the other sprite:
when green flag clicked forever point towards [Sprite2 v] move (5) steps end
This method sort of has a fast wall attraction.
when green flag clicked forever set x to ((10)*(mouse x)) set y to ((10)+(mouse y)) end