Here's a more exhaustive list of features and references:

• Mesh shaders are used to render the 9.7 million leaves in the scene. The mesh shader also performs frustum culling on the GPU, in all passes. Details and performance discussion here.
• A basic scene tree and entity system built on entt. entt is used to group physics bodies, meshes, transforms, materials, instance data and more.
• PBR direct lighting and materials based on UE4's roughness-metallic workflow.
  • Image-based lighting using a BRDF LUT is currently not implemented. Since I was short on time, I used a cheap approximation instead. To compute indirect lighting, the reflected view vector is used to sample the sky dome. A flat ambient term is added to this value and the result is fed to the BRDF. This step is repeated by sampling the sky dome using the surface normal and the two results are combined. Refer to the source here for details.
• GTAO (without bent normals) using XeGTAO.
• Physics simulation and first-person movement using the Jolt physics engine.
• Water simulation using hardware tesselation. Refer to this blog post for details.
• Procedurally generated foliage using L-systems. Details are in this blog post.
• Coarse frustum culling on the CPU. This is done for all passes, including the shadow pass. Details here. The culling frustum can be frozen in place to observe the effects.
• Shadow mapping with large kernel PCF. The shadow frustum is fit around the camera frustum for culling and to make efficient use of the shadow map texels.
• Point lights with shadows. Culling is in place when drawing point light shadows as well.
• Normal mapping without precomputed tangents, as explained by Christian Schüler here.
• A translucency-based subsurface scattering approximation, explained by Alan Zucconi here. This is in turn based on EA's presentation here. I used this for both the water and the leaves.

• This method builds on the work of Thibault Tricard's Interval Shading to draw volumetric particles as tetrahedrons that are composed of participating media.
• Interval Shading uses mesh shaders to splat tetrahedrons to the screen as triangle proxies. Vertex attributes are set in such a way that after rasterization, the pixel shader receives two depths: one for the front face of the tetrahedron and one for the back. This depth interval can then be used for shading.
• Since the medium is represented by a rasterized particle system instead of a density field or voxels, it is easy to animate and can be used for interactive simulations, as demonstrated in the video.
• Radiance is integrated analytically for a single tetrahedron using the depth interval provided by interval shading. The tetrahedrons are sorted and drawn furthest-to-nearest and blending is used to integrate radiance across all particles.
• Self shadowing is achieved by first rendering optical depth into a light-space 3D texture similar to conventional shadow maps. To determine the radiance arriving at any point along a depth interval, this 3D texture is sampled at both interval boundaries and linearly interpolated.
• Some of the planned future work includes:
  • Making the tetrahedron edges less visible.
  • Shadowing of the medium by opaque objects.
  • Casting volumetric shadows onto opaque objects.
  • Performance optimizations:
    • Draw to a lower resolution to reduce pixel shader cost, then upscale and composite.
    • Frustum culling when drawing the volumetric shadow map.
    • Early-Z culling does not work with this method. Therefore, occlusion culling has to be performed in the mesh shader.