I'm going to kind of teach two things here, one how to make an invisible name over a background so that you can only see it when the animation goes over it and the second this is how to do the animation. If you don't want the invisible text just skip the first 3 steps.
**Advantage to invisible text: Hidden until animation goes over it; Disadvantage: Can't move it around without a hassle and can't do special blending effects like bevel emboss to it without it becomming visible**
Step 1
Find a background, duplicate the layer and select the top layer. Now select the Type Tool and set it to 'Create a Mask or Selection'(dotted T) which is next to the font type(Refer to Screenshot below)

Step 2
Find an area on the top layer where you want your hidden text to be and type in the text, the background should create an opaced red layer while you're typing your text. Make sure you get your text in the right area before clicking the Check Mark because if you move it around afterwards, it won't appear invisible.

Step 3
Click the checkbox when you have it in a good spot. You should see a selection appear around your text. Go to Select->Inverse(Shift+Ctrl+I) then hit delete. After you've deleted all but the text area hit Ctrl+D to get rid of the selection dotted line.

Step 4
Now for the animation. Remember this works on normal text too if you don't want that invisible text like I just showed in the first 3 steps. Create a new layer above your first two and select the gradient tool. Have the settings in the screenshot below and create a slanted line or line going in whichever direction you choose.

Step 5
First off in the previous step if you have a darker background you might want to hit Ctrl+I after you create the gradient so that it's white instead of black, or you can change this to any other color you might want it to be. With the gradient layer still selected, hit Ctrl+G so that a little arrow goes from that layer to the text(invisible or not) below it. If it's the invisible text that I taught it will appear as a normal layer not a text layer.

Step 6
Create a new layer over the gradient layer and do the same steps as 4-5 but Have the line slanting the opposite way, if you did a vertical line then just make a duplicate, if you had made a horizontal line then make 1 of the slanted or vertical ones. Make sure after you make the gradient you hit Ctrl+G again so that the arrow is pointing down. If your text has any black or whatever color you made your gradient shining through the text don't worry about it.

Step 7
Once again do the same process but have a horizontal gradient, if you have one horizontal and one slanted/vertical from previously then just create another slanted/vertical. Make sure you create a new layer above the rest and hit Ctrl+G when done.

Step 8
Save this as a photoshop file and open it up in Image Ready. Select the Move tool and on the first gradient you made and put it on the far left of the text just so that you can't see it over the text. On the second gradient you made put it to the far right of the text just so you can't see it on the text, and on the third gradient you made put it above the text just so it isn't showing any. Make sure all of these will beable to go over all of the text when moving from left to right, right to left, or from up to down.

Step 9
Now duplicate the current frame(on bottom of animation box 3 to the right of the play button). On this frame move the first gradient all the way to the RIGHT of the text just so it's not showing, the second gradient to the LEFT of the text just so it's not showing, and the third gradients all the way UNDER the text just so it's now showing. Basically the opposite sides for frame 2 with the gradients.

Step 10(Final Step)
Now Select the First animation frame again. Go to tween(the little circles refer to screenshot below) and make about 50 frames and then hit enter. Go back to the first frame and hit play, it should work. When you save it make sure you go to File->SAVE OPTIMIZED AS-> and then whatever you want it to be but make sure it's in .gif format.

Here's what I got:

If you need any help just PM: Aversa
All creds for this tutorial go to Aversa.
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