How do I create a polygon gradient in photoshop?

Question

I have a pentagon that I want to fill with a gradient. The effect should be that one side of the pentagon is uniformly white, and the two opposite sides are uniformly black, with a smooth transition in between. I've tried doing this by overlapping several linear gradients, but the result just doesn't look smooth.

The effect should be something like this, but better obviously.

I'm using CS6.

Answer 1

1. Create two copies of the shape, one black and one white, with the white shape's layer on top.
2. Put both shapes in a group and create a mask using the area of the shape (Ctrl+Click the layer icon).
3. Blur the white shape and move it as desired.

Answer 2

Make a bigger white shape, insert layer style Inner Glow to it:

Insert an empty top layer, select both layers and apply Layer > Merge Layers (not Merge Down!). Now you have a piece which can be freely splitted:

Before fixing the effect by merging you can play a little with the contour curve to get different gradient.

A way to get very round gradient is to apply Surface blur to the combined version:

Actually the whole process can be based on layering blurred shapes as already said in another answer. But that method becomes complex if you need something like straight sharply beveled edges.

Answer 3

Ok I figured out how to do this, leaving a guide for future me.

1. Create a white shape
2. Apply a horizontal gradient along the shortest side
3. Select just the gradient portion
4. Transform this using warp (Edit->Transform->Warp)
5. Move the point in the bottom right to the bottom right corner, the one above it to halfway along the bottom line, and the one above that to halfway along the top line
6. Voila