11 Replies Latest reply on Jun 11, 2010 12:36 PM by Rick Gerard

    How do you filter out moving objects in a movie?

    HelpThisGuy

      Hello!

      I'v searched the internet for solutions to this but I cann't find any.

      Im prittie new and I need to make a house on fire while two guys (one is me)

      will be walking away from it, towards the camera.

       

      I want to filter out these two guys and only apply fire and flames to the house itself!

      To do this I used Time Diffrence and tried to isolate the guy using Fast Blur and Luma Key

      but Im prittie lost.. Nothing works and I really need guidence

       

      Do you know a trick to use?

      I cant do greenscreening as the green background would cost a fortune..

      But isn't there anyway to filter out moving objects?

        • 1. Re: How do you filter out moving objects in a movie?
          bogiesan-gyyClL Level 3

          Difference Matte is your only viable option as long as you have a clean plate and, if you're as new as you claim, you didn't shoot that.

           

          The best time to ask these questions is before you shoot not after the damage has been done.

           

          Interesting your spellcheck refused to flag "prittie." Even colloquial filtration should have balked at such personal neologisms.

           

          bogiesan

          1 person found this helpful
          • 2. Re: How do you filter out moving objects in a movie?
            Maldar3953

            It's almost impossible to give a solution without seeing the footage.

             

            Good old masking frame-by-frame manually would be most likely the way to go..

            • 3. Re: How do you filter out moving objects in a movie?
              HelpThisGuy Level 1

              Diffrence Matte eyy?

              Im going to try that!

               

              Right now the damage isnt made, i made a test footage to try

              to create the effect before we start shooting the movie

              But right now, if it might be simpler than Diffrence Matte, I got a layer which got my whole body (except some inner parts) coverd up by the color white.

               

              Could I make the white area clearify that no effects should be renderd inside that area and the only the video will be renderd there?

               

              Just asking so if I fail at Diffrence Matte I got another solution to try

              • 4. Re: How do you filter out moving objects in a movie?
                Szalam Adobe Community Professional & MVP

                If you have stuff isolated on a layer you can use the layer as a Track Matte.

                 

                However, as Maldar kinda mentioned, rotoscoping is usually the only way to go. If you have CS5 the Rotobrush Tool can really help speed that process up.

                • 5. Re: How do you filter out moving objects in a movie?
                  HelpThisGuy Level 1

                  Rotorscoping doesnt come in CS4.

                  Sorry I forgot to mention Im using CS4..

                   

                  But for the Diffrence Matte, that is just like Cromakey..

                   

                  Is there a way to put a mask around me and some kind of effect that will

                  adjust it as I move?

                  • 6. Re: How do you filter out moving objects in a movie?
                    Szalam Adobe Community Professional & MVP

                    What you are asking for is rotoscoping. Here is how to do it in AE CS4.

                    • 7. Re: How do you filter out moving objects in a movie?
                      HelpThisGuy Level 1

                      Ahh rotoscoping, thats just putting a mask around the area..

                      That is incredible hard when theres fire in the background, it doesnt look real...

                       

                      I guess I must get a greenscreen area..

                       

                      I wounder how they do in real world..

                      They must really light the place on fire i guess..

                       

                      • 8. Re: How do you filter out moving objects in a movie?
                        Rick Gerard Adobe Community Professional & MVP

                        I'm not sure that you totally get the process. This kind of shot requires at least 3 elements or plates. These three plates become three layers in After Effects. The bottom layer would be the Background Plate which is a shot of the house without any actors in the shot. The next plate would be the Effect Plate or Fire Plate which could be any shot you can get or generate through plug-ins of flames. The top layer would be your Foreground Plate or your two actors.

                         

                        Now that you know what you need you can plan your shoot. The background plate is easy. Just set the camera on a tripod and lock it off. NO zooming. No panning, No change of focus. The foreground plate is also easy. You don't have to green screen the entire set, all you need to do is to put a green screen behind your actors. I do this kind of thing all the time using a 6' X 6' (sometimes smaller) green screen (or blue or red or purple) made of fabric and stretched over a frame that I made from 1/2" EMT electrical conduit and 4 90º elbow connectors for less than $20 at Home Depot or Lowes. You get a couple of assistants to walk behind your actors holding the green screen behind them. If you need to include their feet they can be easily rotoscoped out later and you can garbage matte everything else. If it's impossible to green screen the shot then you are stuck with roto, but that's much easier in CS5 using the roto brush. If you use your show with the actors as the background plate roto is even easier because you can hide a multitude of sins by simply feathering the roto and letting the fire light wrap around the actors a bit.

                         

                        The fire plate can be purchased footage, or you could shoot a real fire against a black background, or you could create the flames using AE or even a 3D app like Blender (free) or a bunch of other apps.

                         

                        Making the shot look real requires a few tricks once you have your clean plates. Fire creates light so you've got to add lighting effects to the background plate to sell the fire. You've also got to wrap light around your actors. Look for tutorials on light wrap for this. You can really help sell the effect if you place some flickering light sources behind and to the side of your actors when you shoot the foreground (actors) plate.

                         

                        Once you get a handle on these techniques it's fairly easy to make the transition to pulling of this kind of a shot with a hand held camera (now you have to learn motion tracking). On a project I recently completed we had to put a fire in a prop fireplace while actors moved around bringing milk and cookies for Santa. It was all roto and the fire was shot at night with nothing more than a black cloth (Duvetyne) behind the fireplace grate. The final composite was 10 layers and was so totally believable that no one questions the shot.

                         

                        The layers were from top to bottom, reflection in grandmas glasses, light wrap, actors (roto of original background plate), fire flicker layer, color mask layer (more orange around fire, fire glow layer, fire layer in Add mode, second fire layer in screen mode, third fire layer Luma keyed, and finally the original plate which contained all the actors, carefully lit with flickering firelight simulated by dangling a stick with fabric cut into 1/2 inch wide strips about one foot long in front of a orange gelled light behind and to the right of  the actors.

                         

                        If I get a chance I'll post a screenshot.

                         

                        Here you go:

                         

                        Light Wrap:

                        ShowingLightWrap.png

                         

                        The Movie

                        Part of the original render before color grading.

                        Enjoy

                        • 9. Re: How do you filter out moving objects in a movie?
                          Szalam Adobe Community Professional & MVP

                          "... rotoscoping, thats just putting a mask around the area..

                          That is incredible hard when theres fire in the background, it doesnt look real...I guess I must get a greenscreen area.."

                          I agree with Mr. Gerard, I don't think you understand the process. The result of green screen and roto is the same. The only benefit to green screen is that you don't have to take the time to do rotoscoping. And, if you do green screen in a different location, it often looks worse because of lighting mismatch. Also, if you're shooting with DV or HDV tape, you get the terribly blocky issues inherent in keying that kind of footage due to the color resolution of those formats. Many of the "real world" special effects you're talking about are done with rotoscoping and some are done with green screen, but it both cases you need to do light wrapping and a lot of other little techniques to sell your shot.

                           

                          Mr. Gerard's post is very in-depth and has some great suggestions. I say you pay close attention to everything he's said. And keep in mind he had ten layers to his comp and that was just for a fireplace. You are going to have a lot more because you're burning down a whole house.

                          • 10. Re: How do you filter out moving objects in a movie?
                            HelpThisGuy Level 1

                            Yes, thanks alot Rick Gerard!

                            I really appriciate that you took your time writing that detailed!

                            Now I know exacly what I am going to do!

                            That idea with having guys walking with the greenscreen behind the

                            actors and then rotoscoping the feet was GREAT!

                            I am going to go with that!

                             

                            Im really thankfull for all that help and I will constantly

                            look at it to tacle my problems

                             

                            Thanks alot to everyone else as well!

                            • 11. Re: How do you filter out moving objects in a movie?
                              Rick Gerard Adobe Community Professional & MVP

                              Loaded up a movie and a still...