I need to understand how to put different textures on each face of a cube (OpenGL ES 1). But i can’t find examples of how to do it
Atm i found an example of how to paint the same texture on all the faces of the cube, but i dont need that
this is the actual code i have:
public class Cube {
/** The buffer holding the vertices */
private FloatBuffer vertexBuffer;
/** The buffer holding the texture coordinates */
private FloatBuffer textureBuffer;
/** The buffer holding the indices */
private ByteBuffer indexBuffer;
/** Our texture pointer */
private int[] textures = new int[1];
/**
* The initial vertex definition
*
* Note that each face is defined, even
* if indices are available, because
* of the texturing we want to achieve
*/
private float vertices[] = {
//Vertices according to faces
-1.0f, -1.0f, 1.0f, //Vertex 0
1.0f, -1.0f, 1.0f, //v1
-1.0f, 1.0f, 1.0f, //v2
1.0f, 1.0f, 1.0f, //v3
1.0f, -1.0f, 1.0f, //...
1.0f, -1.0f, -1.0f,
1.0f, 1.0f, 1.0f,
1.0f, 1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
-1.0f, 1.0f, 1.0f,
-1.0f, -1.0f, -1.0f,
1.0f, -1.0f, -1.0f,
-1.0f, -1.0f, 1.0f,
1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f,
-1.0f, 1.0f, -1.0f,
1.0f, 1.0f, -1.0f,
};
/** The initial texture coordinates (u, v) */
private float texture[] = {
//Mapping coordinates for the vertices
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 0.0f,
1.0f, 1.0f,
};
/** The initial indices definition */
private byte indices[] = {
//Faces definition
0,1,3, 0,3,2, //Face front
4,5,7, 4,7,6, //Face right
8,9,11, 8,11,10, //...
12,13,15, 12,15,14,
16,17,19, 16,19,18,
20,21,23, 20,23,22,
};
/**
* The Cube constructor.
*
* Initiate the buffers.
*/
public Cube() {
//
ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
vertexBuffer = byteBuf.asFloatBuffer();
vertexBuffer.put(vertices);
vertexBuffer.position(0);
//
byteBuf = ByteBuffer.allocateDirect(texture.length * 4);
byteBuf.order(ByteOrder.nativeOrder());
textureBuffer = byteBuf.asFloatBuffer();
textureBuffer.put(texture);
textureBuffer.position(0);
//
indexBuffer = ByteBuffer.allocateDirect(indices.length);
indexBuffer.put(indices);
indexBuffer.position(0);
}
/**
* The object own drawing function.
* Called from the renderer to redraw this instance
* with possible changes in values.
*
* @param gl - The GL Context
*/
public void draw(GL10 gl) {
//Bind our only previously generated texture in this case
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//Point to our buffers
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
//Set the face rotation
gl.glFrontFace(GL10.GL_CCW);
//Enable the vertex and texture state
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
//Draw the vertices as triangles, based on the Index Buffer information
gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer);
//Disable the client state before leaving
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
}
/**
* Load the textures
*
* @param gl - The GL Context
* @param context - The Activity context
*/
public void loadGLTexture(GL10 gl, Context context) {
//Get the texture from the Android resource directory
InputStream is = context.getResources().openRawResource(R.drawable.nehe);
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) {
}
}
//Generate one texture pointer...
gl.glGenTextures(1, textures, 0);
//...and bind it to our array
gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
//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);
//Clean up
bitmap.recycle();
}
}
You’re drawing all 12 triangles of the cube with one call to glDrawElements. During one call to glDrawElements, the GL render state remains constant, and this includes the bound texture. Meaning, you can’t change the texture used for rendering during the call to glDrawElements. So, to use different textures for each cube side, you need separate calls to glDrawElements. Before each call to it, you’ll need to change the bound texture.
There are more advanced methods that would let you do it with a single call for efficiency but let’s not bother with those for now.