57. Don’t Go Chasing Waterfalls

So, I’ve been continuing to bang away on the visuals for the game, which means I could just post up some more screenshots like I did last month, but I thought it might be more fun to do a bit of a technical breakdown of the waterfall effect in the game.

You can see what the finished effect looks like below:

So, there are obviously lots of references I can go to for waterfalls. Photo references, other games. I happen to live near quite a few streams and rivers, many of which have waterfalls.

A few of the bigger influences on this effect are the waterfalls in the Zelda games Breath of the Wild and The Wind Waker. You can see examples of both of those below:

I’m actually not a huge fan of the look of the waterfalls in Breath of the Wild, but the way in which the effect is technically achieved is fairly obvious there, and so I consider it somewhat of an influence on my approach. Really, both of the above waterfall effects, as well as the waterfalls in Taiji are essentially a variant on a basic scrolling texture effect.

Below on the left, you can see the source texture I use for the bulk of the waterfall effect. And on the right you can see and what it looks like when scrolled across a distorted UV map. ( A UV map is what tells the graphics card which part of the 2D texture to draw on each part of a 3D model. In this case, the UVs are stretched in the shader, with the underlying geometry just being a flat rectangle)

So the basis of the effect is that I overlay two copies of this texture, with different offsets and slightly different scrolling speeds. These form the white foam layer.

After that, I make two more layers, only these scroll much faster and are partially transparent. This forms a second layer to go beneath the white layer.

Both these layers are composited together and then overlaid (at a lower alpha and with a fade towards the top) onto a screen-space gradient that acts as the water’s base color. The gradient is subtle but resembles the reflection of a blue sky.

Alright, so we now have the base of our effect, and can add the edges. The edges are just another scrolling texture using the same distorted UVs as before. The left and the right edges are just mirror images of eachother, offset a bit along the direction of scrolling. The UVs for the edge texture are also pinched in a bit at the top of the waterfall. Below, the original edge texture is on the left and how it gets distorted and scrolled is on the right

The black area of the edge texture is used to mask off the effect so that it can be composited into the rest of our effect and blended in. We add a slight fade to transparency at the top of the waterfall and we’ve completed the base effect.

At this point, we add a churn effect to the bottom of the waterfall, using particle systems. One system is emitting large circles which shrink and fade out, the other system emits smaller circles which fly up and then are killed off when they cross the bottom edge of the waterfall. You can see the two particle effects separately below.