How To Reveal Object

[RayDel]

I have attached a picture of an arrow I created to go over top of this image. I would like the arrow to get revealed from the back of the arrow to the front of the arrow. I believe this can be done with a mask but I am not having any luck actually making it reveal from behind the mask. Any help or a better way to do this would be appreciated!

[Rick Gerard · Accepted solution]

It looks like all you have to do is add a comp-sized solid above the Arrow.PNG layer, set the solid as an Alpha Track Matte for the PNG layer, then animate the position of the solid to move it up and out of frame. 

[RayDel]

Rick I am not seeing an option for Alpha Track Matte for the png layer. I toggled the switches button at the bottom but I don't see that alpha option

[Rick Gerard]

I take it that you found it. The UI has changed with the latest versions. Check the new user guide if that is the problem. Just type Track Matte in the Search Help field in the top right corner of After Effects.

[Mylenium]

I'm not even seeing a mask, so I feel inclined to agree with Rick. You may simply need a track matte or a vertical linear wipe. It may just require pre-composing your 3D arrow to work correctly.

Mylenium 

[RayDel]

Thanks, I originally had a track matte but it was not set correct.