Re: [sdljava-users] Incorrect behaviour of glTranslatef() on Linux?

[Ivan Z. G. <iva...@ya...>]

Hi Raffael,

I would have to gamble that glTranslatef() is working correctly.  The
reason is that sdljava only delegates the call to the OpenGL layer and
does nothing special itself.  Unless something funny is happening to the
numbers before they get to the OpenGL layer I can't imagine there to be
a problem.  Conversion of the numbers appropriatly is taken care of by
swig so this should be fairly solid...

Sorry that I can't be more help.

-Ivan/

Raffael Herzog wrote:

>Hi,
>
>I'm having a strange problem with sdljava on Ubuntu Linux (Breezy). I 
>was trying go through the NeHe tutorials, but I already failed in the 
>first lesson because glTranslatef() seems to behave very strangely 
>(maybe incorrectly?).
>
>First the Code:
>
>  gl.glLoadIdentity();
>  gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
>  gl.glColor3f(1.0f, 1.0f, 1.0f); // added by me, to be sure
>  gl.glTranslatef(-1.5f, 0f, -6f);
>
>  gl.glBegin(GL.GL_POLYGON);
>  gl.glVertex3f(0.0f, 1.0f, 0.0f);
>  gl.glVertex3f(-1.0f, -1.0f, 0.0f);
>  gl.glVertex3f(1.0f, -1.0f, 0.0f);
>  gl.glEnd();
>
>  gl.glTranslatef(3.0f, 0.0f, 0.0f);
>
>  gl.glBegin(GL.GL_QUADS);
>  gl.glVertex3f(-1.0f, 1.0f, 0.0f);
>  gl.glVertex3f(1.0f, 1.0f, 0.0f);
>  gl.glVertex3f(1.0f, -1.0f, 0.0f);
>  gl.glVertex3f(-1.0f, -1.0f, 0.0f);
>  gl.glEnd();
>
>  gl.flush();
>  surface.glSwapBuffers();
>
>The problematic line is the 4th one: "gl.glTranslatef(-1.5f, 0f, -6f);"
>
>Like this, all I get is a black window. If I change -6f to 0f, it works 
>correctly, but of course, it's too big, that's why we want to move back 
>first. ;)
>
>The strange thing now is: If I change it to 1f or -1f, I get exactly the 
>same picture as with 0f. If, however, I change it to 1.1f or -1.1f, I'm 
>back at the black window. The x and y axis seem to work correctly.
>
>Do I have to set some flag somewhere with sdljava or is this actually a 
>bug in sdljava (or maybe some sort of incompatibility with Breezy)?
>
>Both OpenGL tests shipped with sdljava work fine BTW, but they don't use 
>glTranslatef(). Oh, and another thing, I also tried replacing 
>glTranslatef() with glTranslated(), but that's just the same thing.
>
>TIA,
>   Raffi
>
>  
>