geigel1 wrote:1. I will be using a photo for the background..how do I make sure it extends for the length of the animation.
Drag the photo onto the timeline, then in the timeline, right-click on the object's main track and choose 'Set Duration'. Enter the new duration that you want.
You can also use the Crop toolbar button (next to the mouse Arrow pointer button) in the timeline to drag the object's length.
geigel1 wrote:2. I am going to composite a creature moving over the photo..but the animation sent me has a black background instead of green..could somebody give me a step by step on how to deal with a black background that I need to remove.
Can you ask whoever created the animation to export it again and include an alpha channel? That's the easiest way.
If not, try setting the object's blend mode to Add or Screen and see if it gives you the desired result. It may, however, create a slight transparency in areas that you don't want to be transparent.
To change an object's blend mode, single click on the object's main track in the timeline to bring up its Object Inspector on the right-hand side. Then change the 'Composite' drop down to whatever blend mode you want.
Also, if you haven't done so already, I recommend you watch the Video tutorials.