// Project 3D point 'a' from world-space to screen-space
func perspProj(a *vec3.T, cam *Camera) *vec2.T {
m := mkExtrinsicCameraMtx(cam)
printM4(m)
sp := vec3.From(a)
m.TransformVec3(&sp)
return &vec2.T{sp[0], sp[1]}
}
func (r *R) drawRadarBeam() {
m := mat3.Ident
m.AssignZRotation(cam.Orientation[0])
view := vec3.UnitX
view.Scale(100) // prescale view vector to take meaningful size on screen
m.TransformVec3(&view)
pos2 := vec3.From(&cam.Pos)
pos2[2] = 0
pos2.Add(&view)
r.sr.SetDrawColor(0, 255, 0, 255)
r.sr.DrawLine(int(cam.Pos[0]), int(cam.Pos[1]), int(pos2[0]), int(pos2[1]))
}
func mkExtrinsicCameraMtx(cam *Camera) *mat4.T {
mRot := mat3.Ident
mRot.AssignEulerRotation(cam.Orientation[0], cam.Orientation[1], cam.Orientation[2])
mRot.Transpose()
printM3(&mRot)
m := mat4.From(&mRot)
mRot.Scale(-1)
camPos := vec3.From(&cam.Pos)
mRot.TransformVec3(&camPos)
m[3] = vec4.From(&camPos)
return &m
}