[OpenGL ES - Android] Better way to generate tiles
- by Inoe
Hi !
I'll start by saying that i'm REALLY new to OpenGL ES (I started yesterday =), but I do have some Java and other languages experience.
I've looked a lot of tutorials, of course Nehe's ones and my work is mainly based on that.
As a test, I started creating a "tile generator" in order to create a small Zelda-like game (just moving a dude in a textured square would be awsome :p).
So far, I have achieved a working tile generator, I define a char map[][] array to store wich tile is on :
private char[][] map = {
{0, 0, 20, 11, 11, 11, 11, 4, 0, 0},
{0, 20, 16, 12, 12, 12, 12, 7, 4, 0},
{20, 16, 17, 13, 13, 13, 13, 9, 7, 4},
{21, 24, 18, 14, 14, 14, 14, 8, 5, 1},
{21, 22, 25, 15, 15, 15, 15, 6, 2, 1},
{21, 22, 23, 0, 0, 0, 0, 3, 2, 1},
{21, 22, 23, 0, 0, 0, 0, 3, 2, 1},
{26, 0, 0, 0, 0, 0, 0, 3, 2, 1},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 1},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
};
It's working but I'm no happy with it, I'm sure there is a beter way to do those things :
1) Loading Textures :
I create an ugly looking array containing the tiles I want to use on that map :
private int[] textures = {
R.drawable.herbe, //0
R.drawable.murdroite_haut, //1
R.drawable.murdroite_milieu, //2
R.drawable.murdroite_bas, //3
R.drawable.angledroitehaut_haut, //4
R.drawable.angledroitehaut_milieu, //5
};
(I cutted this on purpose, I currently load 27 tiles)
All of theses are stored in the drawable folder, each one is a 16*16 tile.
I then use this array to generate the textures and store them in a HashMap for a later use :
int[] tmp_tex = new int[textures.length];
gl.glGenTextures(textures.length, tmp_tex, 0);
texturesgen = tmp_tex; //Store the generated names in texturesgen
for(int i=0; i < textures.length; i++)
{
//Bitmap bmp = BitmapFactory.decodeResource(context.getResources(), textures[i]);
InputStream is = context.getResources().openRawResource(textures[i]);
Bitmap bitmap = null;
try {
//BitmapFactory is an Android graphics utility for images
bitmap = BitmapFactory.decodeStream(is);
} finally {
//Always clear and close
try {
is.close();
is = null;
} catch (IOException e) {
}
}
// Get a new texture name
// Load it up
this.textureMap.put(new Integer(textures[i]),new Integer(i));
int tex = tmp_tex[i];
gl.glBindTexture(GL10.GL_TEXTURE_2D, tex);
//Create Nearest Filtered Texture
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
//Different possible texture parameters, e.g. GL10.GL_CLAMP_TO_EDGE
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT);
//Use the Android GLUtils to specify a two-dimensional texture image from our bitmap
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);
bitmap.recycle();
}
I'm quite sure there is a better way to handle that... I just was unable to figure it. If someone has an idea, i'm all ears.
2) Drawing the tiles
What I did was create a single square and a single texture map :
/** The initial vertex definition */
private float vertices[] = {
-1.0f, -1.0f, 0.0f, //Bottom Left
1.0f, -1.0f, 0.0f, //Bottom Right
-1.0f, 1.0f, 0.0f, //Top Left
1.0f, 1.0f, 0.0f //Top Right
};
private float texture[] = {
//Mapping coordinates for the vertices
0.0f, 1.0f,
1.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f
};
Then, in my draw function, I loop through the map to define the texture to use (after pointing to and enabling the buffers) :
for(int y = 0; y < Y; y++){
for(int x = 0; x < X; x++){
tile = map[y][x];
try
{
//Get the texture from the HashMap
int textureid = ((Integer) this.textureMap.get(new Integer(textures[tile]))).intValue();
gl.glBindTexture(GL10.GL_TEXTURE_2D, this.texturesgen[textureid]);
}
catch(Exception e)
{
return;
}
//Draw the vertices as triangle strip
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
gl.glTranslatef(2.0f, 0.0f, 0.0f); //A square takes 2x so I move +2x before drawing the next tile
}
gl.glTranslatef(-(float)(2*X), -2.0f, 0.0f); //Go back to the begining of the map X-wise and move 2y down before drawing the next line
}
This works great by I really think that on a 1000*1000 or more map, it will be lagging as hell (as a reminder, this is a typical Zelda world map : http://vgmaps.com/Atlas/SuperNES/LegendOfZelda-ALinkToThePast-LightWorld.png ).
I've read things about Vertex Buffer Object and DisplayList but I couldn't find a good tutorial and nodoby seems to be OK on wich one is the best / has the better support (T1 and Nexus One are ages away).
I think that's it, I've putted a lot of code but I think it helps.
Thanks in advance !
