Make certain colors in texture transparent

Troubleshooting graphics
1

Is it possible to make certain colors in texture transparent, like colorkeying?

Or is it possible to replace a certain color with a pixel with alpha=0?

I want to display a crosshair, but the image has a pink background color which I want to make transparent.

2

Have tried unsing a png with an alpha channel? Combined with the use of an AlphaState it should give you what you need.

3

Thank you for answer, but I already have lots of textures and I do not want to change them, I want to solve this programmatically.


4

Only option that comes to my mind is writing a separate program that takes the original image and color value as inputs and outputs a new texture that has alpha channel added. I do not think you would want to do this inside your main program anyways as it seems like something that should be done only 1-ce, not every time the program is started.

5

In directX there is an option when loading a texture to automatically replace a certain color with transparency.

Also the DirectX fixed function AlphaState has the possibility to give a color key which pixels are skipped during rendering.

I expected that at least one of these methods would be possible with jme.



The problem is that Iam a total noob when it comes to graphics editors and I do not know how to use a transparent color.

I've heard only a few programs support that.

6

I'd imagine you'd be able to do it with a pixel shader.

7

According to this thread you’re on the right track with using the transparent render queue, your problem most likely lies in the test functions.

8

Thanks for replying, but I did everything as recommended in this thread, I only use blend and not test.

But as I said, if I try to use QUEUE_TRANSPARENT the crosshair disappears, I don't know whether is has then something to do with the Z-Buffer or whatever :frowning:

9

Hmm… sounds like a good addition to jME's texture utils.

10

OK, I tried doing the same using the same settings you have posted above in the transparent queue, and it worked. So I think you may need to look elsewhere for your problem. Try a simple test case outside your app and see if it works for you.

11

I had to deactivate the Zbuffer for that object to get it working with semi-transparency.



crosshair.setRenderQueueMode(Renderer.QUEUE_ORTHO);



ZBufferState zbs = DisplaySystem.getDisplaySystem().getRenderer().createZBufferState();

zbs.setEnabled(false);

crosshair.setRenderState(zbs);



thank you all for reply.

12

Old thread, but I've the same problem.



What I've done so far is this:


      //Do the crosshair:
      DisplaySystem display = DisplaySystem.getDisplaySystem();
        crosshair = new Node("Crosshair");

        Quad q = new Quad("Crosshair quad", display.getWidth() / 20, display.getWidth() / 20);
        crosshair.attachChild(q);

        TextureState ts = display.getRenderer().createTextureState();
        ts.setTexture(TextureManager.loadTexture(JMEGame.class.getClassLoader().getResource("textures/crosshair.png"),
                Texture.MinificationFilter.BilinearNearestMipMap, Texture.MagnificationFilter.Bilinear));
        ts.setEnabled(true);
        q.setRenderState(ts);

        crosshair.setLightCombineMode(LightCombineMode.Off);
       
        BlendState as = display.getRenderer().createBlendState();
        as.setBlendEnabled(true);
        as.setTestEnabled(false);
        as.setSourceFunction(BlendState.SourceFunction.SourceAlpha);
        as.setDestinationFunction(BlendState.DestinationFunction.OneMinusSourceAlpha);
        as.setEnabled(true);
        crosshair.setRenderState(as);

        crosshair.setRenderQueueMode(display.getRenderer().QUEUE_ORTHO);

        ZBufferState zbs = DisplaySystem.getDisplaySystem().getRenderer().createZBufferState();
        zbs.setEnabled(false);
        crosshair.setRenderState(zbs);
       
        crosshair.setLocalTranslation(new Vector3f(display.getWidth() / 2, display.getHeight() / 2, 0));

        rootNode.attachChild(crosshair);

        crosshair.updateGeometricState(0, true);
        crosshair.updateRenderState();



A simple copy and paste of the above, made in JME 2. My problem: The crosshair is painted white on black. Neither the white nor the black color is transparent! I don't know why! Has anyone a clue?

Thanks!
13

is there an alpha channel in the image you are using for the texture?

14

Yeah… well… you know…



Of course that was the problem! I'm sooo stupid.  Thanks for the tip!!!  :smiley: