Generating terrain

OpenGL OpenGL: Basic Coding
1

I’ve been reading a few online tutorials on how to render terrain and use it with opengl, but I’m having difficulty finding the best solution. I think I need a more in depth study into how best to go by it.

I was wondering whether anyone knows of any good books that I can reference to aid my understanding. I’m using the LWJGL binding of opengl in java, if that matters.

Anyway, any help would be appreciated. Thanks!

Paul

2

Take a look at the 2D Perlin noise function to create height maps.

I used the Simplex noise of Stefan Gustavsson, but I had to tweak the functions a little to get them normalized.

3

Thanks for replying. I’ll do some research into that, cheers.

4

I’m just trying to get this height map working. I’m got a class called Terrain which has a 2D array called ground. This code just loops through the x and z rows/cols and returns the y to the glVertex call. Here’s the code:


	public void drawGround()
	{
		GL11.glBegin(GL11.GL_TRIANGLE_STRIP);
			GL11.glColor3f(1.0f,1.0f,1.0f);
			int h = terrain.ground.length;
			int w = 0;
			if(h > 0)
				w = terrain.ground[0].length;
			float h1 = 0.0f;
			float h2 = 0.0f;
			for(int x = 1; x < h; x++)
			{
				for(int z = 1; z < w; z++)
				{
					h1 = terrain.ground[x][z];
					if(x + 1 < h)
						h2 = terrain.ground[x + 1][z];
					else
						h2 = 0.0f;
					GL11.glVertex3f(x * 10.0f,h1,z * 10.0f);
					GL11.glVertex3f((x + 1) * 10.0f,h2,z * 10.0f);
				}
			}
		GL11.glEnd();
	}

It seems to be working almost perfectly, except there seems to be this one line that goes right down each column, presumably because I haven’t finished the last triangle row.

Here’s an image of what this produces:

http://i.imgur.com/CjDDF.png

The Terrain class is basically structured:


class Terrain
{

public float[][] = new float[][]
{
{0.0f,0.0f,0.0f, ...},
{0.0f,0.0f,0.0f, ...},
{0.0f,0.0f,0.0f, ...},
...
}
};

Just in case you wanted to know. Can you see any way of solving this, or is there perhaps a better method of implementing this?

Thanks,

Paul

5

It is impossible to find the “best” solution that suites all needs. What kind of terrain are you trying to implement?

Probably one of the most versatile books about terrain rendering is:
3D Engine Design for Virtual Globes

Also, many state-of-the-art solutions can be find in:
Virtual Terrain Project

6

Cheers mate, that’s exactly what I needed. I’ll give those a look through.

7

i guess you can get rid of the extra lines by putting the glBegin/glEnd commands into the first loop:

for(int x = 1; x < h; x++)
{
GL11.glBegin(GL11.GL_TRIANGLE_STRIP);
for(int z = 1; z < w; z++)
{
…
}
GL11.glEnd();
}

8

Ah, I see. So it having numerous calls to glBegin wouldn’t be an inefficient way to implement a sort of mesh terrain?

9

Very inefficient, if there are a bunch of them. They basically break a batch (a group of triangles/primitives that are sent to the GPU to be drawn together in one go).

Also, I think in some past posts, folks have observed with some drivers that display lists don’t optimize across Begin/End boundaries.

Generally speaking, break a batch when you need to perform a state change, but otherwise avoid doing so (unless you’ve just got a ton of vertices in your batch already, or you’re view-frustum culling groups of triangles).