102 lines
2.7 KiB
Go
102 lines
2.7 KiB
Go
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package cube
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import (
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"github.com/go-gl/mathgl/mgl64"
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"math"
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)
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// Rotation describes the rotation of an object in the world in degrees. It
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// holds a yaw (r[0]) and pitch value (r[1]). Yaw is in the range (-180, 180)
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// while pitch is in the range (-90, 90). A positive pitch implies an entity is
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// looking downwards, while a negative pitch implies it is looking upwards.
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type Rotation [2]float64
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// Yaw returns the yaw of r (r[0]).
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func (r Rotation) Yaw() float64 {
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return r[0]
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}
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// Pitch returns the pitch of r (r[1]).
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func (r Rotation) Pitch() float64 {
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return r[1]
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}
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// Elem extracts the elements of the Rotation for direct value assignment.
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func (r Rotation) Elem() (yaw, pitch float64) {
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return r[0], r[1]
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}
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// Add adds the values of two Rotations element-wise and returns a new Rotation.
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// If the yaw or pitch would otherwise exceed their respective range as
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// described, they are 'overflown' to the other end of the allowed range.
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func (r Rotation) Add(r2 Rotation) Rotation {
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return Rotation{r[0] + r2[0], r[1] + r2[1]}.fix()
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}
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// Opposite returns the Rotation opposite r, so that
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// r.Vec3().Add(r.Opposite().Vec3()).Len() is equal to 0.
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func (r Rotation) Opposite() Rotation {
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fixed := r.fix()
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return Rotation{fixed[0] + 180, -fixed[1]}.fix()
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}
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// Neg returns the negation of the Rotation. It is equivalent to creating a new
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// Rotation{-r[0], -r[1]}.
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func (r Rotation) Neg() Rotation {
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fixed := r.fix()
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return Rotation{-fixed[0], -fixed[1]}
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}
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// Direction returns the horizontal Direction that r points towards based on the
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// yaw of r.
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func (r Rotation) Direction() Direction {
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yaw := r.fix().Yaw()
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switch {
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case yaw > 45 && yaw <= 135:
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return West
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case yaw > -45 && yaw <= 45:
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return South
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case yaw > -135 && yaw <= -45:
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return East
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case yaw <= -135 || yaw > 135:
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return North
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}
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return 0
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}
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// Orientation returns an Orientation value that most closely matches the yaw
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// of r.
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func (r Rotation) Orientation() Orientation {
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const step = 360 / 16.0
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yaw := r.fix().Yaw()
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if yaw < -step/2 {
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yaw += 360
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}
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return Orientation(math.Round(yaw / step))
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}
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// Vec3 returns the direction vector of r. The length of the mgl64.Vec3 returned
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// is always 1.
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func (r Rotation) Vec3() mgl64.Vec3 {
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yaw, pitch := r.fix().Elem()
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yawRad, pitchRad := mgl64.DegToRad(yaw), mgl64.DegToRad(pitch)
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m := math.Cos(pitchRad)
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return mgl64.Vec3{
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-m * math.Sin(yawRad),
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-math.Sin(pitchRad),
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m * math.Cos(yawRad),
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}
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}
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// fix 'overflows' the Rotation's values to make sure they are within the range
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// as described above.
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func (r Rotation) fix() Rotation {
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signYaw, signPitch := math.Copysign(180, r[0]), math.Copysign(90, r[1])
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return Rotation{
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math.Mod(r[0]+signYaw, 360) - signYaw,
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math.Mod(r[1]+signPitch, 180) - signPitch,
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}
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}
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