描述

The density of something is defined as its mass per unit volume, which basically means how much mass is crammed into the space it takes up in the world. 所以气球的密度很小，因为它的质量很小，占据很大的空间，而铅棒的密度很高，因为它的质量很大，而且空间很小。

In the GameMaker Studio 2 2D physics world mass is calculated automatically for you from the values you input for the density and by the surface area of the shape you define for the fixture. 这将直接影响固定装置具有多少惯性以及如何对碰撞和力产生反应，因此，如果你制造出高密度的小形状，则会产生非常大的质量效应（如铅棒）但是如果你定义了一个较小密度的大形状，那么它的质量效应会更小（像一个气球）。

NOTE: If you wish the instance that is going to receive the fixture to be static (ie: immobile in the game world) then the density should be set to 0, essentially giving it an infinite density.

语法：

physics_fixture_set_density(fixture, density)

返回：

N/A（无返回值）

例如：

physics_fixture_set_density(fix_Balloon, 0.1);

The code above will set the density of the fixture indexed in "fix_Ballon" to 0.1.