Global pos to camera view



  • On 01/03/2018 at 11:46, xxxxxxxx wrote:

    How i can convert global coordinates of object in relation to specific camera view?
    I've managed to create a Python Generator which returns quad polygon with points linked to top-left, top-right, bottom-right and bottom-left coordinates of camera-view:

    import c4d,math
    # Cam Quad Maker
      
    def fov(fv) : #get FoV-point
        return math.tan(fv*.5)
      
    def main() :
        op[c4d.ID_BASEOBJECT_ABS_POSITION] = c4d.Vector(0)
        op[c4d.ID_BASEOBJECT_ABS_ROTATION] = c4d.Vector(0)
        op[c4d.ID_BASEOBJECT_ABS_SCALE] = c4d.Vector(1)
        cam=op[c4d.ID_USERDATA,1] #Link-field for Camera
        if(not cam)or(cam.GetType()!=c4d.Ocamera) :
            return None
        cMat=cam.GetMg() #camera-matrix
        cZ=cam[c4d.CAMERAOBJECT_TARGETDISTANCE] #z-distance
        cvH=fov(cam[c4d.CAMERAOBJECT_FOV])*cZ #view-Horz
        cvV=fov(cam[c4d.CAMERAOBJECT_FOV_VERTICAL])*cZ #view-Vert
        qd=c4d.BaseObject(c4d.Opolygon)
        pts=[c4d.Vector(0,0,0)]*4
        pts[0]=c4d.Vector(-cvH,-cvV,cZ)*cMat #topLeft
        pts[1]=c4d.Vector(cvH,-cvV,cZ)*cMat #topRight
        pts[2]=c4d.Vector(cvH,cvV,cZ)*cMat #botRight
        pts[3]=c4d.Vector(-cvH,cvV,cZ)*cMat #botLeft
        qd.ResizeObject(4,1)
        qd.SetAllPoints(pts)
        qd.SetPolygon(0,c4d.CPolygon(0,1,2,3))
        return qd
    

    Now i want to convert another object's coordinates relatively to this quad so in resulting coords:

    • X will be 0 if object exactly on the left edge, 1 if on the right, <0 if out of view on the left and >0 if on the right
    • Y will be same as X but relative vertically
    • Z will be 0 if object exactly on the plane formed by the quad points, <0 if it's farther and >0 if closer to camera

    But i don't sure what to do next =) When i multiply obj.GetMg().off by pts[0] for example (TopLeft point of view) i get some garbage values, it's definitely not what i wanned lol
    And cuz i have pretty crappy knowledge of trigonometry i'm kinda stuck now =\



  • On 01/03/2018 at 14:35, xxxxxxxx wrote:

    Well, i found a way to do what i wanted:

    import c4d,math
    # Object Pos related to CamView
      
    def fov(fv) : #get FoV-point
        return math.tan(fv*.5)
      
    def main() :
        cam=op[c4d.ID_USERDATA,1] #Link-field for Camera
        if(not cam)or(cam.GetType()!=c4d.Ocamera) : return None
        obj=op[c4d.ID_USERDATA,2] #Link-field for Object
        if(not obj) : return None
        cMat=cam.GetMg() #camera-matrix
        cZ=cam[c4d.CAMERAOBJECT_TARGETDISTANCE] #z-distance
        cvH=fov(cam[c4d.CAMERAOBJECT_FOV])*cZ #view-Horz
        cvV=fov(cam[c4d.CAMERAOBJECT_FOV_VERTICAL])*cZ #view-Vert
        bd=doc.GetActiveBaseDraw()
        bd.InitializeView(doc, cam, True)
        oMat=obj.GetMg() #object-matrix
        v=bd.WC(oMat.off) #World2Camera
        v[0]=(v[0]+cvH)/cvH*.5
        v[1]=1-(v[1]+cvV)/cvV*.5
        v[2]=(cZ-v[2])/cZ
        op[c4d.ID_USERDATA,3]=str(v) #Output coords into string-field
        return None
    

    But if anyone who's not THAT retarded in 3D math as i am will provide code to do the same without BaseView.WC() via basic matrix/vector equations i will absolutely appreciate it.



  • On 02/03/2018 at 11:02, xxxxxxxx wrote:

    Hi Markus, thanks for writing us.

    With regard to your request, consider that using the BaseView::WS() and BaseView::GetSafeFrame() are the easiest and fastest way to deliver a world-to-screen representation of the space which, in my opinion, fits better with what you're looking for.

    Slightly modifying the code it should look like:

      
    import c4d  
    # Object Pos related to CamView  
      
    def main() :  
      cam = op[c4d.ID_USERDATA,1] #Link-field for Camera  
      if(not cam)or(cam.GetType()!=c4d.Ocamera) :   
          return None  
        
      obj = op[c4d.ID_USERDATA,2] #Link-field for Object  
      if(not obj) :   
          return None  
        
      cZ = cam[c4d.CAMERAOBJECT_TARGETDISTANCE] #z-distance  
        
      bd = doc.GetActiveBaseDraw()  
      
      objPos = obj.GetMg().off #object global position  
      
      v = bd.WS(objPos) #World2Screen  
      sf = bd.GetSafeFrame() #SafeFrame  
        
      v[0] = (v[0] - sf["cl"])/(sf["cr"]-sf["cl"])  
      v[1] = (v[1] - sf["ct"])/(sf["cb"]-sf["ct"])  
      v[2] = (cZ-v[2])/cZ  
      
      op[c4d.ID_USERDATA,3]=str(v) #Output coords into string-field  
        
      return None  
    

    Best, Riccardo


Log in to reply