You also need some sort of 3d Tracking software, like Matchmover. This will allow you to gather data from your video footage that can be duplicated in a 3d program so that the 3D camera will match the one used to take the video. This is very important or the bear will not properly "fit" into the scene. Lighting becomes very critical in the 3d world as well. When you see on the making of documentaries in a scene where there is going to be 3d stuff added later, they will hold up a shiny globe and a camera will take a picture of it. This will pinpoint the locations of the realworld lights and their colors. This image is then taken into a program that calculates the contrast and colors within the picture and then spits out data that will be used to create a lighting scheme within the 3d program that will replicate the real world lighting. You can download a program(freeware) that will take jpeg images that were shot of of a chrome globe and do the calculations of the lighting. I know that it can import into Maya. I can't remember what it is called, you can look for it on the web under "HDRI lighting".