Way too many terrain vertices - How can I reduce them?

Troubleshooting graphics
1

Hi,

I am using jMonkey’s ImageBasedHeightMap class to load a Heightmap, and I am then creating a new TerrainQuad from this heightmap:

Texture heightMapImage = manager.loadTexture(file);
    heightmap = new ImageBasedHeightMap(heightMapImage.getImage());
    heightmap.setHeightScale(2);
    heightmap.load();
    
    
    int patchSize = 256;
terrain = new TerrainQuad("Map", patchSize, 513, heightmap.getHeightMap());

The problem is that the terrain has far too many vertices. As I am loading 12 * 12 (144) chunks in total, this is amounting to be quite a lot of vertices.

Take a look at this picture:

The vertex count there is far, far, too high. That same terrain could easily be approximated without much visual loss with less than a quarter of the vertices shown in that picture.

I understand that the terrain is split up into x vertices no matter if it is flat, hilly, or whatever. This is not what I’m asking for - I’m asking how I can just flat-out reduce the vertex count in the terrain for everything.

(Even my powerful PC can’t cope with 10 million vertices)

I am aware that I could export smaller heightmaps, load smaller terrain quads, and then scale them up. Unfortunately, this is not possible due to quirks of the world generator that I use, and JME does not let heightmaps be larger than the TerrainQuads, and the setSize() method on the ImageBasedHeightMap class seems to be useless for this purpose.

Yes, I do have LOD on the terrain, but it doesn’t seem to help much.

Thanks,
Joe

(Note: I managed to duplicate the same terrain in Java & LWJGL with just 512 vertices per chunk, and it still looked fine. No LOD algorithms either)

2

In your case, what might work out better is custom genrated and decimated meshes as tiles. Maybe in a low and a high variant, and just load them when near enough. Smaller gaps at the boraders are easily hidden, by lowering the last vertice a bit.

3

Luckily, it is possible for me to use the terrain generator I use (L3DT) to export meshes.

How can I create a TerrainQuad from an OBJ model (or similar file format)?

4

Ah L3DT, in that case export obj and convert to j3o to improve performance at runtime.

I had written down from a few years ago:
Coordinate System : XZ plane, Y UP
Face winding CW(DirectX)
Origin at center: false
At least that worked for me back a few years I’m not sure how valid this still is.

5

You should be using PerspectiveLodCalculator to compute LOD levels for terrain. It is the most efficient algorithm available. You can specify a quality level too, letting you change the quality / performance tradeoff.

6

Yay, I now have a terrain loaded from OBJ meshes and only about 800 vertices each.

:smiley:

Only problem is, I can’t work out how to make the PerspectiveLodCalculator work on the Spatial that is my terrain. Could someone help me with that?

7

PerspectiveLodCalculator is designed to work with the jME terrain system, like the code you posted in your first post. You can’t use it on regular meshes.