glDrawElements does not show anything when I move it to another method - c++

Question

When I draw terrain like this - it works normal
void Terrain::RenderLandscape()
{
int x, y;
int Index = 0;
for (int i = 0; i < MapSize-1; i++)
{
Index = 0;
for (int j = 0;j < MapSize-1; j++)
{
x = j * Zoom;
y = i * Zoom;
TextureMap[Index+0][0]= j * TextureBit;
TextureMap[Index+0][1]= i * TextureBit;
TextureMap[Index+1][0]= j * TextureBit;
TextureMap[Index+1][1]= (i+1) * TextureBit;
VertexMap[Index+0][2] = HeightMap[j][i];
VertexMap[Index+1][2] = HeightMap[j][i+1];
VertexMap[Index+0][0] = x;
VertexMap[Index+0][1] = y;
VertexMap[Index+1][0] = x;
VertexMap[Index+1][1] = y+Zoom;
Index += 2;
}
glDrawElements(GL_TRIANGLE_STRIP, Index, GL_UNSIGNED_INT, Indices);
}
}
But when I move loops to another method and leave in RenderLandscape
void Terrain::RenderLandscape()
{
glDrawElements(GL_TRIANGLE_STRIP, 512, GL_UNSIGNED_INT, Indices);
}
Where 512 - size of Indices array - It shows only black screen without terrain.
What is the problem?
I move loops to method which is called before renderLandscape. There I initialize vertex, normals, texture arrays. Method init.
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer (3, GL_FLOAT, 0, VertexMap);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 0, TextureMap);
glEnableClientState(GL_NORMAL_ARRAY);
glNormalPointer(GL_FLOAT,0, NormalMap);
for (int Row = 0; Row < MapSize*2; Row++)
{
Indices[Row] = Row;
}
int x, y;
int Index = 0;
for (int i = 0; i < MapSize-1; i++)
{
Index = 0;
for (int j = 0;j < MapSize-1; j++)
{
x = j * Zoom;
y = i * Zoom;
TextureMap[Index+0][0]= j * TextureBit;
TextureMap[Index+0][1]= i * TextureBit;
TextureMap[Index+1][0]= j * TextureBit;
TextureMap[Index+1][1]= (i+1) * TextureBit;
VertexMap[Index+0][2] = HeightMap[j][i];
VertexMap[Index+1][2] = HeightMap[j][i+1];
VertexMap[Index+0][0] = x;
VertexMap[Index+0][1] = y;
VertexMap[Index+1][0] = x;
VertexMap[Index+1][1] = y+Zoom;
Index += 2;
}
}
Index = 0;
for(int i = 0; i < MapSize - 1; i++)
{
Index = 0;
for (int j = 0;j < MapSize-1; j++)
{
CVector3 vTriangle[] = { CVector3(VertexMap[Index + 0]),
CVector3(VertexMap[Index + 1]),
CVector3(VertexMap[Index + 2]) };
CVector3 normal = Normal(vTriangle);
NormalMap[Index + 0][0] = normal.x;
NormalMap[Index + 0][1] = normal.y;
NormalMap[Index + 0][2] = normal.z;
NormalMap[Index + 1][0] = normal.x;
NormalMap[Index + 1][1] = normal.y;
NormalMap[Index + 1][2] = normal.z;
NormalMap[Index + 2][0] = normal.x;
NormalMap[Index + 2][1] = normal.y;
NormalMap[Index + 2][2] = normal.z;
Index += 3;
}
}
So it works like this
1) I initialize opengl and create terrain object.
........
landscape.Init();
glutPassiveMotionFunc(MousePassive);
glutIdleFunc(draw)
........
2) in method draw I call renderLandscape method
glPushMatrix();
glTranslatef(-20, 0, 0);
glScalef(0.01, 0.01, 0.01);
glRotatef(90, 1, 0, 0);
landscape.RenderLandscape();
glPopMatrix();