func (p *PerspectiveCamera) UpdateProjectionMatrix() {
var fov = math3d.RadToDeg(2 * math.Atan(math.Tan(math3d.DegToRad(p.Fov)*0.5)/p.Zoom))
if p.FullWidth > 0 {
var aspect = p.FullWidth / p.FullHeight
var top = math.Tan(math3d.DegToRad(fov*0.5)) * p.Near
var bottom = -top
var left = aspect * bottom
var right = aspect * top
var width = math.Abs(right - left)
var height = math.Abs(top - bottom)
p.ProjectionMatrix.MakeFrustum(
left+p.X*width/p.FullWidth,
left+(p.X+p.Width)*width/p.FullWidth,
top-(p.Y+p.Height)*height/p.FullHeight,
top-p.Y*height/p.FullHeight,
p.Near,
p.Far,
)
} else {
p.ProjectionMatrix.MakePerspective(fov, p.Aspect, p.Near, p.Far)
}
}
/**
* Uses Focal Length (in mm) to estimate and set FOV
* 35mm (full-frame) camera is used if frame size is not specified;
* Formula based on http://www.bobatkins.com/photography/technical/field_of_view.html
*/
func (p *PerspectiveCamera) SetLens(focalLength, frameHeight float64) {
if frameHeight == -1 {
frameHeight = 24.0
}
p.Fov = 2 * math3d.RadToDeg(math.Atan(frameHeight/(focalLength*2)))
p.UpdateProjectionMatrix()
}