Midgard

Overview

Thor and the Midgard Serpent is a low-poly battle scene by MrEmjeR, licensed CC BY 4.0. I found it in the pmndrs viking-ship example, lit by a bright sunset. Here it's relit for night, the sky is new, and there's weather.

The idea

I wanted to see how far the same model could go the other way: the middle of the night, in a storm, in the middle of the fight. The model already has Thor throwing lightning at the serpent. The storm gives that lightning a sky to come from.

Under the hood

• Nothing downloaded but the model. The example lit everything with a sunset HDR fetched from a CDN. Here the light comes from the scene itself: the burning fort, a lantern on deck, the serpent's eyes and the lightning, plus a sky drawn in a shader. The model went from 572 KB to 512 KB: empty meshes and unused textures removed, parts flattened, the ship's objects merged into one draw call.
• Lightning. Four bolts are built once from a seed, all in one mesh, and a strike only sets a few numbers. Each strike has a leader and two to four return strokes tens of milliseconds apart. The bolt flickers with every stroke, but the sky and fog get one soft swell, so the screen never flashes more than about three times a second.
• The water is still the example's glass block, so you see the serpent's coils and the keels through it. Glass renders the scene a second time each frame to refract it; here that second render runs at half resolution, since the water blurs it anyway. The whole island rocks on a slow swell.
• Rain and embers. 2,000 drops in one draw call fall through a box that wraps around the camera in the vertex shader, so the CPU never moves them. Embers from the burning fort drift on the same wind.

The sky is also baked once into an environment map, so the ship, the rock and the serpent pick up the same blues as the water.