I'm using the explode modifier and I want to try to make my object explode from left to right. I know you can do this with gradient textures but the only tutorial I saw either used Blender Render or was outdated. Does anyone know how you could achieve this?
You do not need to do anything special to the partial system. Just have the particle type set to Emitter and emitting from the vertices with Random unchecked.
The particles are emitting from the vertices according to the vertices' indexes, so if you reorder the indexes it will explode in a different order.
Reordering the indexes is very easy. Just select the whole object, then as explained in my answer here, just go to the 3D view header then Mesh > Sort Elements > View X axis (or accessible via the search menu).
That is all it takes to reorder particles. However you will now need to press the Refresh button on the Explode modifier.