How can I use TextureRenderer to render an image to the screen with an alpha ...

OpenGL Development JOGL Development
#1

value. I have rendered jpgs, pngs, etc with alpha=1.0 making this:

mi= TextureRender…
dest=mi.createGraphics();

[…]

mi.beginOrthoRendering(w,h);
dest.drawImage(Img,x,y,java.awt.color.WHITE,null);
mi.sync(0,0,w,h);
mi.drawOrthoRect(0,0);
mi.endOrthoRendering();

…

Is this well done?

Now, I’m trying to render these lines with GL_BLEND activated , but doesn’t work. What’s wrong?

#2

Hard to tell without a test case. Make sure you requested an alpha channel in the TextureRenderer and 8 bits of alpha in your GLCapabilities, and that you have the glBlendFunc set up correctly. Take a look at the demos.j2d package in the jogl-demos workspace for some examples of using the TextureRenderer and other helper classes.

#3

Is the code I wrote well done?

#4

I don’t see anything wrong with it, although so far we have suggested you do all Graphics2D drawing operations and the sync() call before beginOrthoRendering() / draw() / endOrthoRendering().

#5

Thanks Ken. I’ll take a look at those demos for the alpha matter. Is any demo specially good for that matter?

#6

demos.j2d.TestTextureRenderer is probably the closest to what you’re doing.

#7

I’ve seen it . And I`ve done something like this:

mi = new TextureRenderer
dest=mi.createGraphics();
GL gl=auto.getGL(); //auto is the GLAutoDrawable

dest.drawImage(Img…)
mi.sync(—)
mi.beginOrthoRendering(0,0,auto.getWidth(),auto.getHeight());
gl.glEnable(GL.GL_BLEND);
gl.glColor4f(0.5f,0.5f,0.5f,0.5);
gl.glBlendFunc(GL.GL_SRC_ALPHA,GL.GL_ONE);
mi.drawOrthoRect(0,0);
mi.endOrthoRendering();
gl.glDisable(GL.GL_BLEND);

It is doing more or less what I expected, but varying alfa with gl.glColor4f is doing nothing. And , if I change de blending parameters for GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA) doesn´t work ¿?

#8

I see. Internally the TextureRenderer is making a call to gl.glTexEnvi(GL.GL_TEXTURE_ENV, GL.GL_TEXTURE_ENV_MODE, GL.GL_REPLACE). If you make a similar call after beginOrthoRendering() with GL_MODULATE instead of GL_REPLACE that should have the effect you’re after. The TextRenderer does this to support its setColor() method, but I hadn’t expected that people would generally do this with the TextureRenderer’s results. Let me know if you think this should be added to the TextureRenderer’s API.

#9

Let me explain what I’m doing and sorry for my horrible English. I’m trying to do fade effects with videos and pictures over 3D scenes. So I think, I need this feature . I would be grateful if you decide to support Alpha parameter into drawOrthoRect or something so, like in TextRenderer is supported

#10

I’ve pulled the setColor() methods up to the TextureRenderer class. Please try a nightly build of JOGL dated 2/20 or later and post if you see any problems with the new methods.

#11

Thanks . I’ve solved already it looking at the source. The trick was disabling and enabling the depth test because orthorendering is another quad. But thank you very much. I will test it too. I’m very grateful to you and your interest. I think this project is a superproject because the persons which are supporting it.