Thread: Terrain generation (DX9)

heres the code i use to generate/draw terrain:

Code:

void Create_cVertex(cVertex *p_Vertex, float fX, float fY, float fZ, float fTU, float fTV)
{
	p_Vertex->x = fX;
	p_Vertex->y = fY;
	p_Vertex->z = fZ;
	p_Vertex->tu = fTU;
	p_Vertex->tv = fTV;
	p_Vertex->color = D3DCOLOR_XRGB(255, 255, 255);
}

#define TILES_X 64
#define TILES_Y 64

// Globals:

cVertex terrain[TILES_X * TILES_Y][4];
IDirect3DTexture9 *texture; //already loaded elsewhere

void GenerateTerrain()
{
	memset(&terrain, 0, sizeof(terrain));

	unsigned int x, y;
	float SIZEX = 0.5f, SIZEY = 0.5f;

	srand(timeGetTime());

	for (x = 0; x < TILES_X; ++x)
	{
		for (y = 0; y < TILES_Y; ++y)
		{
			Create_cVertex(&terrain[y + (x * TILES_Y)][0], SIZEX * y, rand() % 2, SIZEY - SIZEX, 0, 0);
			Create_cVertex(&terrain[y + (x * TILES_Y)][1], SIZEX * y, rand() % 2, SIZEY, 1, 0);
			Create_cVertex(&terrain[y + (x * TILES_Y)][2], SIZEX * (y + 1), rand() % 2, SIZEY - SIZEX, 0, 1);
			Create_cVertex(&terrain[y + (x * TILES_Y)][3], SIZEX * (y + 1), rand() % 2, SIZEY, 1, 1);
		}

		SIZEY += 0.5f;
	}
}

void DrawTerrain()
{
	unsigned int x, y;

	for (x = 0; x < TILES_ROW; ++x)
	{
		for (y = 0; y < TILES_COLUMN; ++y)
		{
			g_Device->SetTexture(0, texture);
			g_Device->DrawPrimitiveUP(D3DPT_TRIANGLESTRIP, 2, terrain[y + (x * TILES_Y)], sizeof(cVertex));
		}
	}
}

That works fine for flat terrains, but when i added (rand() % 2) to the y value of each vertex, i get really messed up tiles (image attached).

Also, ive been looking through a few sites, and ive noticed that this person did it differently, using only 3 vertices for each tile and his results seem fine, but its in OpenGL and he uses X and Z instead of X and Y.. Is his method better? and if so, how can i convert his code to work with DirectX.

Thanks in advance.

Code:

void UpdateView()
{
  D3DXMATRIX matIdentity, matView, matProjection;

  D3DXVECTOR3 vLookatPt(User.x, User.y, User.z);
  D3DXVECTOR3 vUpVec(0.0f, 1.0f, 0.0f);
  D3DXVECTOR3 vEyePt(User.x, Camera.y, User.z + Camera.z);
  
  D3DXMatrixIdentity(&matIdentity);
  D3DXMatrixLookAtLH(&matView, &vEyePt, &vLookatPt, &vUpVec);
  D3DXMatrixPerspectiveFovLH(&matProjection, D3DXToRadian(60), (float)g_DisplayMode.Width / (float)g_DisplayMode.Height, 1.0f, 50000.0f);

  g_Device->SetTransform(D3DTS_PROJECTION, &matProjection);
  g_Device->SetTransform(D3DTS_WORLD, &matIdentity);
  g_Device->SetTransform(D3DTS_VIEW, &matView);
}

user.* is just a struct i use to move around the terrain
camera.y = 5.0f; (so its looking down on the terrain)
camera.z = -3.0f; (so its a 3rd person camera, ie. its 3 units behind user.z)

what do you mean by not having a grid? heres a screenshot in wireframe mode, it seems to have a grid..

btw, about the lightmap, i was going to add that once i figured out how i could fix this problem, because the only way i know atm, is to edit 4 different vertices for 1 point on the terrain to .. elevate, im guessing this is because i use 4 vertices per square, and no index buffer. Is there a better way? like maybe sharing the vertices from the previous tile, and so on, that might work out better

I would share the vertices. It is more efficient not to, but it adds flexibility to the system if you do - at the small cost of memory which by today's standards isn't even a consideration.

There is no way that is the same image as the top one, just in wireframe mode. The first one is a huge mess of oddly placed triangles. If you perturb the y values of the vertices in the second picture - you should get a terrain.

Iterate through the array and change the y values. If you are using an array, they should all be shared.

Triangle 1 - 0,1,2
Triangle 2 - 1,3,2

01
23

1 Quad.

So your grid will look like this:
0145
2367

or something close to it.

If you have all your vertices in an array indexed 0 to n-1, then create an array of render indices that specify the drawing order for your mesh. for example

Code:

say your 2D array is represented as a 1D array like the element indices below:
1 2 3 
4 5 6
7 8 9

ex. array vaules (heights):
heights = {
23 45 60
32 35 63
63 53 55
}

now create an array which specifies the rendering order.. for triangle strips it could be as follows.
renderIndices = { 1 4 2 5 3 6 9 5 8 4 7 }

image #1 has vertices going from v1 to v4 on the first line
image #2 has vertices going from v1 to v14 on the first line

i just googled a bit more and found an article with image #1, as you can see, he defined the first row up to v9. in image #2 (my method), i defined the first row up to v15, because i use 2 vertices for 1 point most of the time.

my question is, if i defined it like in image #1, up to v9, how would i render it? the creation is easy, the rendering part i dont understand, since the first triangle is v0 - v1 - v5 instead of v0 - v1 - v2.

>>my question is, if i defined it like in image #1, up to v9, how would i render it?

just like i explained above if you want one continuous triangle strip. Maybe it would be easier for you to start with rendering individual rows of triangle strips.

looky...

Code:

for (int i = 0; i < height - 1; i++) {
  beginTriangleStrip
  for (int j = 0; j < width; j++) {
    render vertex i * width + j
    render vertex (i + 1) * width + j
  }
  endTriangleStrip
}

so, from your image above... it would render v0, v5, v1, v6, v2, v7 etc....
what Bubba and i are suggesting is to pre-calculate these render indices and store them in an array. This makes using vertex arrays (or whatever DX calls it) easy and rendering faster.