I'm making something like ars magica's nexi and I was wondering what the easiest way to render a circle is.

That depends entirely on what, exactly, you're doing.

My best guess is that you want a texture file and to draw it with the tessellator.

I was planning on using the tessellator but I wasn't sure if there was some open GL wizardry that could draw a circle instead of me making a texture for it. Or some other renderer that can handle circles.

Yes, it's called DynamicTexture, which is still rendered as a quad with the tessellator.

 

Protip:

It is easier to draw a circle with MSPaint and save it as a texture file than to programatically generate the pixel data one pixel at a time.

Hi

 

This code snippet may help, if all you want to do is draw a circle (ring)

 

  /**
   * Draw an arc centred around the zero point.  Setup translatef, colour and line width etc before calling.
   * @param radius
   * @param startAngle clockwise starting from 12 O'clock (degrees)
   * @param endAngle (degreesO
   */
  void drawArc(double radius, double startAngle, double endAngle, double zLevel)
  {
    final double angleIncrement = Math.toRadians(10.0);
    float direction = (endAngle >= startAngle) ? 1.0F : -1.0F;
    double deltaAngle = Math.abs(endAngle - startAngle);
    deltaAngle %= 360.0;

    startAngle -= Math.floor(startAngle/360.0);
    startAngle = Math.toRadians(startAngle);
    deltaAngle = Math.toRadians(deltaAngle);

    GL11.glBegin(GL11.GL_LINE_STRIP);

    double x, y;
    double arcPos = 0;
    boolean arcFinished = false;

    do {
      double truncAngle = Math.min(arcPos, deltaAngle);
      x = radius * Math.sin(startAngle + direction * truncAngle);
      y = -radius * Math.cos(startAngle + direction * truncAngle);
      GL11.glVertex3d(x, y, zLevel);

      arcFinished = (arcPos >= deltaAngle);
      arcPos += angleIncrement;
    } while (!arcFinished && arcPos <= Math.toRadians(360.0));      // arcPos test is a fail safe to prevent infinite loop in case of problem with angle arguments
    GL11.glEnd();
  }

 

-TGG

I think I'm just gonna use a texture, it looks easier to do.