Monday, March 31, 2008

Brute … not so bad

I started working on my terrain implementation for nebula over the weekend. I chose to do a brute force implementation first just to get the hang of concepts like generating vertices from height map values and generating texture coordinates.

When I initially developed an interest in making games, I never thought I would have to do a terrain, I remember skipping the terrain chapter in a DirectX book I was reading back then. Needless to say I went back to said chapter over the weekend.

I now have a brute force terrain renderer which uses nebula’s default standard shader with a diffuse texture stretched over the terrain. You can imagine that the texture up close is anything but pretty.

Here is how it works. The terrain object requires an input heightmap with 8 bits per pixel. You may also provide a tile size parameter which is used to determine the number of vertices required plus to control the resolution of the terrain. A higher tile size means less vertices and a less smooth terrain.

Say we provide a heightmap of 1024 x 1024 pixels, a terrain of 1024 x 1024 units will be generated. If we had set the tile size to 32, we will end up with a vertex every 32 pixels/units. Therefore we will end up with 33 x 33 vertices for a 1024 x 1024 unit terrain which is pretty decent but what I’m most impressed about is the frame rate. I’m getting a frame rate of about 120 on a laptop with an intel chip though its still needs work on the texturing.

My plan was to get a basic brute force implementation rendering then immediately move on to a chunk lod implementation. Right now, I’m actually thinking I can get away with brute force so I’m looking at whether I can add texture splatting to it and see how far I can get with it.

A question for anyone who can provide some insight on using triangle strip primitives. According to the direct sdk docs, every 2nd triangles should be oriented reversed for it to work properly. I can’t get the terrain to render properly using triangle strips. Looking at the bottom of the terrain, I see holes on every 2nd triangles and from the top it seems fine but I can see hanging meshes on some parts of the terrain.

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