I'm trying to make an animation of a person (first person perspective) walking in the grass. I want to make as if the grass is moving "towards the camera" to make it seem as if the person "in the camera" is moving forward. I am completely lost!
If it's just a simple scene with a plane of grass and a camera, you can either animate the plane of grass horizontally towards the camera, or animate the camera forward along the plane of grass - the end result will be the same. For example, if your camera is looking in the positive Z direction, either move the plane in the negative Z direction (decrease its Z position) or move the camera further along the positive Z direction. Create a position keyframe at one point in time, move later in time and create another keyframe where the plane or camera has changed its position along the Z axis. Keyframing the zoom of the camera would also create a similar look, but would not work if you intend to have the character move in more than one direction. To avoid such issues, and especially if there are other objects in the scene, I would suggest animating the camera position, which is analogous to the motion of the character anyway.
you could use a particle system to create a grass field and then push a 3d camera thru it. you'll likely have issues with the camera moving thru a blade/stalk of grass, though.
to quickly demonstrate, create a new comp, and use the pen tool to quickly make a simple blade of grass (like a long skin triangle with 3 clicks).
make the fill color solid green and then hide that layer.
create a new solid and add Particle World.
in the particle settings, set the particle type to texture quad polygon then set the texture to your grass shape layer. increase the birth and death size to 1 or 2 (maybe larger), rotation speed to zero and initial rotation to 15-30 or so. also set the max opacity to 100 and make the opacity map a straight line at the top of the graph (by default it is ramped at the left and right, make that a solid dark gray rectangle)
in the physics settings set velocity and gravity to zero.
in the producer settings set radius x and z to 1 or so.
at the top of the effect, set the longevity to the length of the comp and keyframe the birth rate to go from 200 or so to 0 over on frame.
you should have a simple field of grass.
now you can add a single node camera and animate it along it's z axis to move thru the grass.
a particle system like Particular would also allow you to create a spherical field that could move with the camera to push grass out of the way of the camera...