Terrain Optimization

The camera behavior in a project that utilizes a Landscape Terrain object plays an important role. A static camera implies a single load of data, provided all textures fit in the video memory. When the active camera significantly changes its position and orientation while unveiling unloaded areas, streaming may hit hard on performance. Therefore, performance and memory consumption should be considered and tuned for the final set of cameras and screen resolution of the target platform.

For convenient profiling, you can animate the camera movement via Tracker and run animations for tests.

It is recommended to use the Microprofile tool for detailed in-depth estimation for the performance of a Landscape Terrain object.

By using the Rendering Performance Profiler, you can estimate the memory consumption.

Hardware Recommendations#

The number and density of different Landscape Layer Maps that define the look of the terrain at the current moment is an important factor — multiple blended layers with high resolution textures might make a significant performance drop. In most cases it is reasonable to combine multiple textures into a single one in a raster graphics editor.

The Current Data Density value for a Landscape Layer Map is calculated based on its spatial size and the resolution of base textures used. It's hard to miss that a decent high-detailed landscape would require a texture tileset of an extremely large resolution.

Also, the visibility of layers is taken into account — if a large Landscape Layer Map overlaps other layers (has a higher Order value), only its graphic data will be loaded and rendered.

Streaming is based on using previously loaded geometry to define the visible areas of terrain. There is no loaded geometry at the very world startup, so the system looks for a Landscape Layer Map that has the Culling flag enabled and loads preliminary low-level data of this layer. If your world contains several layers, one of which represents the basic shape of the terrain, while others are used as insets placed within the bounds of the base layer and having an insignificant height difference from it, it is recommended for you to disable Culling for insets and enable it for the base layer. This is how you can reduce load on CPU at the world startup.

Each frame the Landscape Terrain system checks which tiles are to loaded and updated. Increase the Tiles Update Per Frame parameter to ensure that all necessary tiles are updated on time. However, if this value is too big, it may cause a performance drop during data streaming.

The loading speed of chunks of graphic data depends on the Tiles Load Per Frame value. Higher values imply faster multi-threaded loading of tiles but more performance-consuming data streaming. Note that it is pointless to set this value higher than the Tiles Update Per Frame.

Thus, it is necessary to find a trade-off when tweaking these parameters.

Use the Landscape Terrain VT Streaming helper (or the render_show_landscape_terrain_vt_streaming 1 console command) to enable visualization of tiles being streamed. In this mode colored areas show the tiles that are currently being rendered in a lower resolution until the highest mip-level is loaded and rendered. The faster the colored tiles disappear, the better.

Cache#

Run-Time Modification#

The Landscape Terrain enables you to add up to 1024 details to a mask making it possible to create a pretty detailed and diverse look of the landscape. In terms of optimization, minimizing the number of details and textures is a way to faster rendering.

The textures of details are loaded at the world startup and kept in the video memory to be blended with the base textures of the Landscape Terrain when rendering. You can specify a lower resolution for the corresponding textures of all detail materials by tweaking the following parameters:

• Detail Albedo Texture Resolution
• Detail Height Texture Resolution
• Detail Additional Mask Texture Resolution

The final textures for tiles of the Landscape Terrain are written to the Virtual Texture components (Albedo, Normal and Height). Increase the Texture Memory Size value to ensure that the Virtual Texture provides enough capacity to store the loaded high-detail texture chunks.

With a lower size the Virtual Texture requires less video memory but doesn't provide enough capacity to store all the required data resulting in poor performance, low detail level and fast flickering of the Landscape Terrain surface due to continuous reloading of tiles.

Polygons of the Landscape Terrain surface are adaptively tessellated on the fly and displaced based on the Heightmap component of the Virtual Texture. The polygon mesh is split up to multiple levels of detail of various density depending on the distance from the camera. The Geometry settings provide much room for rendering optimization.

Pay attention to the following parameters:

• With lower values of Geometry Progression less polygons are generated at a distance.
• By configuring the Geometry Polygon Size parameter you can define the minimum spatial size of polygons in case of excessive detail level.
• Geometry Subpixel Reduction parameter determines the minimum ratio of polygon size (in the screen space) to the area seen in the viewport. This parameter enables you to quickly decrease the number of polygons or simply remove too small polygons that are barely visible, in order to increase performance.
• Set a lower Visibility Distance to discard rendering of too remote polygons.

You can decrease the maximum allowed level of detail for the albedo, normal and height textures of the Landscape Terrain by increasing the Texel Size parameter.

Decrease Target Resolution—the resolution of the screen buffer for the Landscape Terrain renderer—to gain more performance at a cost of visual quality.

You can also reduce the detail level of polygons facing the camera at oblique viewing angles (Detail Level By Angle) to optimize streaming load and memory consumption.

Different mip-levels of landscape textures are used at different distances. Switch to the Low or Medium Texture Filtering quality to improve performance at a cost of a slightly visible edge between adjacent mipmap levels.

Culling Optimization#