How to know in OPenGL ES android that one object crosses another?

Question

I have 2 objects on the screen:

static:

non-static:

non-static object moves randomly over the screen.

How do I know that non-static Object cross the "+" (static).

Both objects I draw by using followed code:

private void updateScreenData(float screenWidth, float screenHeight){
    // takes screen Height and Width
    this.mScreenWidth = (screenWidth > 0) ? screenWidth : 1f;
    this.mScreenHeight = screenHeight;
    wRatio = 10f/mScreenWidth;
    hRatio = mScreenHeight/10f;     
}

protected void drawTarget(GL10 gl){
    gl.glPushMatrix();
    try {           
        float transx =  shiftX + (wRatio * (x)); 
        float transy =  shiftY +(mScreenHeight*wRatio) - (wRatio * (y)) - 1/hRatio; 

        gl.glTranslatef(transx, transy, 0.0f);

        //###########  draw ##############

        gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);

        gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, floatBufferArray[mFrame]);

        //update();

        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
        gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, vertices.length / 3);
        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

        //###############################

    } catch (NullPointerException e) {
    }
    gl.glPopMatrix();   
}

public void loadTextures(GL10 gl) {
    Log.e(LOG_TAG, "loadTextures");  

    InputStream is;

    is = mContext.getResources().openRawResource(_SRC);

    Bitmap bitmap = BitmapFactory.decodeStream(is);

    try {
        is.close();
        is = null;
    } catch (IOException e) {
    }

    gl.glGenTextures(TEXTURE_COUNT, textures, 0);

    gl.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
    gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
    GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0);

    bitmap.recycle(); 


}

Any ideas?

What do I need to compare in both Objects?

[EDIT]

I see my question is not so clear, so i'll try once more.

Since my cross image stays at the middle of screen (screenWidth/2 and screenWidth/2) I know the coordinates, it do not change. But second Object changes.

How can I fetch out coordinates (aka x,y) from dynamic object?

Answer 1

One of the simplest and fastest ways is to compare the bounding boxes of the two, and see if they intersect/overlap. This is usually fairly trivial.

In your case, it seems like you have a "hit zone" in the middle of your crosshairs. I would alternatively check if the bounding box of that inner area overlaps the skulls, and if it does, that's a valid hit.

You can see this question's answers for some ways to calculate overlap/intersection..