High Definition (HD) Terrain Technology Overview

By Tony_Hilliam, June 09 2023

High Definition (HD) terrain represents a significant advancement in Trainz, delivering unprecedented levels of detail and precision. HD terrain increases the number of data samples for a given terrain area by 6,400x as compared to classic 10m terrain, meaning that sharp and jaggy edges for terrain shaping and texturing are totally eliminated.

So what techniques have we employed to achieve this massive increase in detail?

First up is 'tessellation', which is a GPU-based technique that generates a high number of polygons and allows us to dynamically adjust the number of polygons in various parts of the scene. It is the linchpin of our new Level of Detail (LOD) implementation. 

With tessellation, we can generate a high density of polygons close to the camera for a highly detailed, realistic view. Conversely, for areas farther from the camera, tessellation generates fewer polygons, aiding performance by reducing the rendering load. It provides us the flexibility to strategically allocate system resources to where they're most visually impactful, without overwhelming the hardware.

Another critical element is 'displacement mapping'. While the LOD system maintains high detail where it matters most, we can leverage displacement mapping to push the amount of intricate detail possible even further. Displacement mapping interpolates between data points based on height data from the ground textures, and modifies the actual ground geometry at even finer resolutions. This method effectively prevents the 'jelly-like' warping noticed on sharp edges with conventional parallax rendering.

Another important consideration is how to handle all the extra data that is being pushed around. The answer to this issue is to utilize "lossy" data compression. This is a crucial component in our strategy to deliver HD terrain without overwhelming your system. This form of compression allows us to significantly reduce the data size by eliminating less important information. Unlike lossless compression, which preserves all data, lossy compression is designed to remove data while keeping the perceptible difference in our game environment to an absolute minimum.

It's a delicate balance – reducing the data enough to manage system requirements, but not so much that it detracts from the overall visual experience.  It allows us to pack in all those extra details brought by the 6,400x resolution increase and displacement mapping without swamping your system with unmanageable amounts of data.

Of course, the extent of these graphics improvements relies heavily on the capabilities of your hardware. To cater to a broad spectrum of hardware profiles, we offer three shader quality settings for HD terrain:

  • "Basic" shader quality is designed for maximum performance, ideal for devices not primarily meant for gaming.
  • "Standard" shader quality offers a balance between performance and visual quality, fitting for mid-range or older gaming devices.
  • "Extreme" shader quality will offer the highest possible visual experience for those with modern, high-end gaming machines, albeit still with some performance trade-off.

Each setting has been carefully calibrated to deliver the best possible experience on your hardware.