diff --git a/physics.go b/physics.go index 3542ec6..ef3a31e 100644 --- a/physics.go +++ b/physics.go @@ -40,16 +40,17 @@ type Vector struct { // Gravity is a utility vector that represents gravity in 2D and 3D contexts, // assuming that your coordinate plane looks like in 2D or 3D: // -// -y -y ±z +// y y ±z // │ │ / // │ │/ // └───── ±x └───── ±x // -// Note: Gravity usually is -9.81m/s however we use a positive value because we -// assume the origin is placed at the top-left corner and that downward is the -// positive y direction (only if using this utility variable). -// Otherwise, you can place the origin wherever you'd like. -var Gravity = Vector{0, 9.81, 0} +// (i.e. origin is located in the bottom-left corner) +var Gravity = Vector{0, -9.81, 0} + +// TerminalGravity is a utility vector that represents gravity where +// the coordinate plane's origin is on the top-right corner +var TerminalGravity = Vector{0, 9.81, 0} // NewProjectile accepts a frame rate, and initial values for position, velocity, and acceleration and // returns a new projectile.