// Vec3Diff returns the rotation quaternion between two vectors.
func Vec3Diff(a, b *vec3.T) T {
cr := vec3.Cross(a, b)
sr := math.Sqrt(2 * (1 + vec3.Dot(a, b)))
oosr := 1 / sr
q := T{cr[0] * oosr, cr[1] * oosr, cr[2] * oosr, sr * 0.5}
return q.Normalized()
}
func (c *FreeFlightCamera) Lift(dist float32) {
position := vec3.T(c.Pos)
forward := vec3.T(c.Forward())
right := vec3.T(c.Right())
up := vec3.Cross(&forward, &right)
up.Scale(dist)
c.Pos = Vec3(vec3.Add(&position, &up))
}
func (rt *Raytracer) calcIncVectors(camera Camera, size image.Point) (vec3.T, vec3.T, vec3.T) {
width := float32(size.X)
height := float32(size.Y)
lookAtPoint := vec3.T(camera.LookAt())
eyePoint := vec3.T(camera.Position())
up := vec3.T(camera.Up())
viewDirection := vec3.Sub(&lookAtPoint, &eyePoint)
u := vec3.Cross(&viewDirection, &up)
v := vec3.Cross(&u, &viewDirection)
u.Normalize()
v.Normalize()
viewPlaneHalfWidth := float32(math.Tan(float64(rt.cfg.FieldOfView / 2)))
aspectRatio := height / width
viewPlaneHalfHeight := aspectRatio * viewPlaneHalfWidth
sV := v.Scaled(viewPlaneHalfHeight)
sU := u.Scaled(viewPlaneHalfWidth)
lookV := vec3.Sub(&lookAtPoint, &sV)
viewPlaneBottomLeftPoint := vec3.Sub(&lookV, &sU)
xIncVector := u.Scaled(2 * viewPlaneHalfWidth)
yIncVector := v.Scaled(2 * viewPlaneHalfHeight)
xIncVector[0] /= width
xIncVector[1] /= width
xIncVector[2] /= width
yIncVector[0] /= height
yIncVector[1] /= height
yIncVector[2] /= height
return xIncVector, yIncVector, viewPlaneBottomLeftPoint
}
func (c *FreeFlightCamera) Right() Vec3 {
up := vec3.T(c.Up())
forward := vec3.T(c.Forward())
return Vec3(vec3.Cross(&up, &forward))
}
// Cross returns the cross product of two vectors.
func Cross(a, b *T) T {
a3 := a.Vec3DividedByW()
b3 := b.Vec3DividedByW()
c3 := vec3.Cross(&a3, &b3)
return T{c3[0], c3[1], c3[2], 1}
}