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

[Raffael H. <her...@ra...>]

Hi,

I'm having a strange problem with sdljava on Ubuntu Linux (Breezy). I=20
was trying go through the NeHe tutorials, but I already failed in the=20
first lesson because glTranslatef() seems to behave very strangely=20
(maybe incorrectly?).

=46irst 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=20
correctly, but of course, it's too big, that's why we want to move back=20
first. ;)

The strange thing now is: If I change it to 1f or -1f, I get exactly the=20
same picture as with 0f. If, however, I change it to 1.1f or -1.1f, I'm=20
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=20
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=20
glTranslatef(). Oh, and another thing, I also tried replacing=20
glTranslatef() with glTranslated(), but that's just the same thing.

TIA,
   Raffi

=2D-=20
The difference between theory and practice is that in theory, there is
no difference, but in practice, there is.

he...@ra... =B7 ICQ#67961355 =B7 PGP Key 5D1FF5F4 =B7 www.raffael.ch