RE: [Csgl-users] Trouble with CsGL and rotating.

[Ben H. <be...@ex...>]

The problem you have isn't with CsGL but rather with the OpenGL API.

glRotate excepts as its parameters an angle of rotation and a vector
around which to rotate.  You are currently giving a vector of rotation
of (1.0f, 1.0f, 0.0f).  This is not a unit vector.  Because it isn't a
unit vector I am not surprised that this operation is causing a scaling
issue.  I would normalize that vector and see if that works.

-ben
www.exocortex.org


> -----Original Message-----
> From: csg...@li... 
> [mailto:csg...@li...] On Behalf Of 
> Michael Shafrir
> Sent: Thursday, July 10, 2003 8:59 AM
> To: csg...@li...
> Subject: [Csgl-users] Trouble with CsGL and rotating.
> 
> 
>   I am writing an app in C# (VS.NET). I am using CsGL for 
> some basic OpenGL stuff. I want to draw an x,y, and z axes in 
> the control, and then rotate the view so that it looks 3D - 
> if you draw the axes and don't rotate them, you wouldn't be 
> able to see the Z axis.
> 
>   Here's my code, which I based mainly on 
> (http://www.componentsnotebook.com/notebooks/csharp/csgl.aspx)
> . You will see that I called GL.glRotatef(10.0f, 1.0f, 1.0f, 
> 0.0f); at one point. I picked 1.0 for the angle arbitrarily; 
> however, no matter what angle I choose, it only seems to make 
> the axes smaller. Please help, and if there are any questions 
> ask away!
> 
>   Btw, this is how the axes look before I rotate: 
> http://www.terptrader.com/normalaxis.png
>   And after I rotate: http://www.terptrader.com/rotatedaxis.png
>   My goal is to have the axes look 3D, like in this picture: 
> http://wonkosite.ausbone.net/vrml/axis.gif
> 
> 
> 
>   If you could help I would really appreciate it because I am 
> completely stumped right now.
> 
> 
> 
>               private void drawAxis()
> 
>               {
> 
>                     double left = 0.05 * Size.Width;
> 
>                     double right = 0.95 * Size.Width;
> 
>                     double bottom = 0.05 * Size.Height;
> 
>                     double top = 0.95 * Size.Height;
> 
>                     double origin_x = Size.Width / 2;
> 
>                     double origin_y = Size.Height / 2;
> 
> 
> 
>                     // draw X axis
> 
>                     GL.glBegin( GL.GL_LINES );
> 
>                     GL.glVertex3d( left, origin_x, 0 );
> 
>                     GL.glVertex3d( right, origin_x, 0 );
> 
>                     GL.glEnd();
> 
> 
> 
>                     // draw Y axis
> 
>                     GL.glBegin( GL.GL_LINES );
> 
>                     GL.glVertex3d( origin_y, bottom, 0 );
> 
>                     GL.glVertex3d( origin_y, top, 0 );
> 
>                     GL.glEnd();
> 
> 
> 
>                     // draw Z axis
> 
>                     GL.glBegin( GL.GL_LINES );
> 
>                     GL.glVertex3d( origin_x, origin_y, 0.0 );
> 
>                     GL.glVertex3d( origin_x, origin_y, 1.0 );
> 
>                     GL.glEnd();
> 
> 
> 
>                     GL.glFlush();
> 
>               }
> 
> 
> 
>               public override void glDraw()
> 
>               {
> 
>                     GL.glRotatef(0.5f, 0.0f, 1.0f, 0.0f);
> 
>                     drawAxis();
> 
>               }
> 
> 
> 
>               protected override void InitGLContext()
> 
>               {
> 
>                     GL.glClearColor( 1.0f, 1.0f, 1.0f, 0.0f );
> 
>                     GL.glColor3f( 0.0f, 0.0f, 0.0f );
> 
>                     GL.glPointSize( 4.0f );
> 
>               }
> 
> 
> 
> 
> 
>               protected override void OnSizeChanged(EventArgs e)
> 
>               {
> 
>                     base.OnSizeChanged(e);
> 
> 
> 
>                     GL.glClear(GL.GL_COLOR_BUFFER_BIT | 
> GL.GL_DEPTH_BUFFER_BIT);                                      
>     // Clear Screen And Depth Buffer
> 
>                     GL.glMatrixMode(GL.GL_PROJECTION);
> 
>                     GL.glLoadIdentity();
> 
>                     GL.glOrtho( 0.0, Size.Width, 0.0, 
> Size.Height, 1.0, -1.0 );
> 
>                     GL.glMatrixMode(GL.GL_MODELVIEW);
> 
>               }
> 
> 
> 
> 
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