jPCT - a 3d engine for Java => Support => Topic started by: tomzwo on March 10, 2005, 10:10:27 am

Title: Applying Colors to Objects - a possible solution
Post by: tomzwo on March 10, 2005, 10:10:27 am
JPCT documentation states that objects may have textures (handled by the singleton TextureManager) - and that's it, full stop.

In a gaming environment this is all very well (since game artefacts and levels have to be designed via tools or similar) and in sophisticated object management scenarios, too - but in a simple situation you might want to be able to apply colors programmatically. At least, I wanted to...

The solution I found is based on TextureManager's ability to load from a stream (some code parts omitted):

Code: [Select]

// we have a color associated with an object (in this case within another class)
if(this.theColor != null)
// create identifying string (see below)
String tmp = new colorHelper(this.theColor).x11String();
// do we have the texture ?
          if(txman.containsTexture(tmp) == false)
// create the texture - see below
            InputStream in;
            if((in = cr.createTexture(this.theColor)) != null)
              txman.addTexture(tmp, new Texture(in));
// ja: zuweisen

the identifying string is quite easy (normal X11-Style)
Code: [Select]

  public String x11String() {
    String rv = "#";
    String tmp;

    tmp = Integer.toHexString(this.red);
    rv += (tmp.length() >= 2 ? "" : "0") + tmp;
    tmp = Integer.toHexString(this.green);
    rv += (tmp.length() >= 2 ? "" : "0") + tmp;
    tmp = Integer.toHexString(this.blue);
    rv += (tmp.length() >= 2 ? "" : "0") + tmp;
    return(new String(rv));

so far, nothing special - let's have a look at the creating method (this does not really match the call above, since my classes are a little more complicated) - createTexture is basically a call to createPngImageStream below with createImage and a fixed size of 8x8 which is perfectly sufficient

Code: [Select]

  public InputStream createPngImageStream(Image img)
    if(img == null)
    PngEncoder enc = new PngEncoder(img);
    byte[] results = enc.pngEncode();
    return(new ByteArrayInputStream(results));

  public Image createImage(int width, int height, Color color)
    int[] pixels = new int[width * height];
    int n;
      pixels[n] = color.getRGB();
    return(this.createImage(width, height, pixels));

  private Image createImage(int width, int height, int[] pixels)
    DirectColorModel cm = new DirectColorModel(32, 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000);
    MemoryImageSource prod = new MemoryImageSource(width, height, cm, pixels, 0, width);

// durch das Toolkit sind wir von Komponenten unabhaengig
    Toolkit tk = Toolkit.getDefaultToolkit();
    Image img = tk.createImage(prod);

(the code above could be simplified for demonstration purposes, but - frankly - I do not feel like it)

I found the PngEncoder mentioned at http://www.chemaxon.com/marvin/doc/user/PngEncoder.java (the encoder there is GPL'ed); in its original version a few things have to be deleted from the source code (just calls to a progress displaying object). I'm using this encoder because my application needs to run in Java 1.1 environments - for Java 2 the builtin encoder methods might be a better idea.

Of course, this is somewhat crude - maybe a future version of TextureManager might be able to read from an Image...? (pretty please)

Also: this has not been tested outside my development environment so far (JDK 1.4.2 / Windows). I'll post updates as soon as I know more.

Comments welcome.

Of course, using a different algorithm for the pixel array, it is possible to create bit-patterned multicolor thingies (I do this, too)
Title: Applying Colors to Objects - a possible solution
Post by: tomzwo on March 10, 2005, 10:12:10 am
and... while we're at it, there's a question I have, too: how can I display object edges in a different color (if it's possible at all) - meaning something like a mixture of wireframe and solid model in order to be able to view objects more clearly?
Title: Applying Colors to Objects - a possible solution
Post by: EgonOlsen on March 10, 2005, 11:08:46 pm
Adding a constructor that takes an Image should be easy and may appear in one of the next versions. Anyway, thanx for sharing the code. May i ask what kind of project that is?
Title: Applying Colors to Objects - a possible solution
Post by: tomzwo on March 12, 2005, 01:50:09 pm
basically its a simple object editor integrated into a (web) shop system: customers are able to configure products from a set of components and order them. 3D is the icing on the cake in order to give them an idea of the result. Depending on my customer, I'll post a link as soon as it's online and I'm allowed to...

have you thought about my question (edged in different color)?
Title: Applying Colors to Objects - a possible solution
Post by: EgonOlsen on March 16, 2005, 07:40:24 am
Quote from: "tomzwo"
have you thought about my question (edged in different color)?
Opps, i must have missed this one...to keep it short: That's hardly possible in jPCT without adding additional geometry that simulates it. You may draw a wireframe over the rendered scene, but that's most likely not what you want.