Ok, so i\'m not following your tutorials(i\'m really sorry) and i found guy who implemented heightmaps thingie. Ok, so, he made the system who reads the bitmap file and do some shit with it, after that system needs to make all terrain with triangles. so as i know, quad is made out of 2 triangles, one triagle is made out of 3 vertices. so 3+3=6. So why does he do this 12 times?

    	for(j=0; j<(m_terrainHeight-1); j++)
	{
		for(i=0; i<(m_terrainWidth-1); i++)
		{
			index1 = (m_terrainHeight * j) + i;          // Bottom left.
			index2 = (m_terrainHeight * j) + (i+1);      // Bottom right.
			index3 = (m_terrainHeight * (j+1)) + i;      // Upper left.
			index4 = (m_terrainHeight * (j+1)) + (i+1);  // Upper right.

			// Upper left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index3].x, m_heightMap[index3].y, m_heightMap[index3].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Upper right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index4].x, m_heightMap[index4].y, m_heightMap[index4].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Upper right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index4].x, m_heightMap[index4].y, m_heightMap[index4].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index1].x, m_heightMap[index1].y, m_heightMap[index1].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index1].x, m_heightMap[index1].y, m_heightMap[index1].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Upper left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index3].x, m_heightMap[index3].y, m_heightMap[index3].z);
			vertices[index].color = D3DXVECTOR4(0.0f, 0.0f, 0.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index1].x, m_heightMap[index1].y, m_heightMap[index1].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;

			// Upper right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index4].x, m_heightMap[index4].y, m_heightMap[index4].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;

			// Upper right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index4].x, m_heightMap[index4].y, m_heightMap[index4].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index2].x, m_heightMap[index2].y, m_heightMap[index2].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom right.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index2].x, m_heightMap[index2].y, m_heightMap[index2].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;

			// Bottom left.
			vertices[index].position = D3DXVECTOR3(m_heightMap[index1].x, m_heightMap[index1].y, m_heightMap[index1].z);
			vertices[index].color = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 1.0f);
			indices[index] = index;
			index++;
		}
	}

P.S. dont judge me, i don\'t know how to properly use code thingie.