question

Hi,

Using lower-resolution textures is not to reduce texture sampling cost, it is to reduce overall memory usage. It is theoretically possible (albeit rather complex) to dynamically stream the required mipmaps from disk, but this is not a feature we have at the moment.

For memory optimization, there are a few key elements:

• it is important that lower resolution LoDs use less memory
• multiple (or even all) LoDs may be loaded and displayed at the same time, thus exist in memory at the same time

Consider two different cases.

1. You have a model which exists only once in the world. In this case, only one LOD will persist in memory. To facilitate fast loading/unloading of the model, it helps if the textures are shared between the LODs. For memory purposes, this is not as important, but it can still help to reduce memory spikes when streaming in LODs.
2. You have a model which exists multiple times in the world. Think of multiplayer aircraft, or props such as lanterns. In this case, multiple LODs may persist in memory (the model can be displayed far away and close by at the same time). To reduce the total memory footprint, it is crucial that textures are shared as much as possible between the LODs. At the same time, if the model is only displayed once, but far away, you want a small memory footprint. If vertex coloring does not cut it, and you need a texture for a faraway model, having a small texture (instead of some 2k maps you may have) can help reduce memory usage.

A final note. You say: "to create additional materials and textures for each LOD leads to a contradictory effect in optimization". In reality, due to the way our engine (and the LOD system) works, materials are not shared between different LODs, only textures. As you say, to create additional textures seems contradictory. I believe duplicating textures should only be done if texture memory for a given LOD can not be reduced through different means. For example, simply by removing textures from a material, or using vertex colors. Vertex color is great, as it is practically free.

In the documentation, it currently says:

Prefer low-resolution textures for LoDs below the approximate 5% "minSize", eg: try to keep this as 64x64px or smaller.

We will change this to be a bit more clear on the intention behind it:

When reducing texture memory for lower resolution LODs, if it is not possible to remove more textures, use lower resolution textures instead (and make them small, e.g. 64x64px or smaller).