no display name and no $DISPLAY environment variable
    while executing
"load /enadisk/commun/linux/local/ActiveTcl-8.6.11/lib/libtk8.6.so Tk"
    ("package ifneeded Tk 8.6.11" script)
    invoked from within
"load /commun/linux/local/ActiveTcl-8.6.11/lib/Img1.4.6/libtkimgwindow1.4.6.so"
    ("package ifneeded img::window 1.4.6" script)
    invoked from within
"package require img::window"
    ("package ifneeded Img 1.4.6" script)
    invoked from within
"package require Img"
    (in namespace eval "::request" script line 13)
    invoked from within
"namespace eval ::request $script"
    ("::try" body line 12)
OUTPUT BUFFER:
# Lesson28.tcl
#
# David Nikdel & NeHe's Bezier Tutorial
#
# This Code Was Published By Jeff Molofee 2000
# Code Was Created By David Nikdel For NeHe Productions
# If You've Found This Code Useful, Please Let Me Know.
# Visit My Site At nehe.gamedev.net#
#
# Modified for Tcl3D by Paul Obermeier 2006/08/29
# See www.tcl3d.org for the Tcl3D extension.

package require Img
package require tcl3d 0.5.0

# Font to be used in the Tk listbox.
set listFont {-family {Courier} -size 10}

# Determine the directory of this script.
set gDemo(scriptDir) [file dirname [info script]]

# Display mode.
set fullScreen false

# Window size.
set gDemo(winWidth)  640
set gDemo(winHeight) 480

set rotz      0.0               ; # Rotation about the Z axis
set rotzSpeed 0.5               ; # Rotation increment, i.e. speed
set showCPoints true            ; # Toggles displaying the control point grid (NEW)
set divs 7                      ; # Number of intrapolations (conrols poly resolution) (NEW)

# Show errors occuring in the Togl callbacks.
proc bgerror { msg } {
    tk_messageBox -icon error -type ok -message "Error: $msg\n\n$::errorInfo"
    ExitProg
}

# Print info message into widget a the bottom of the window.
proc PrintInfo { msg } {
    if { [winfo exists .fr.info] } {
        .fr.info configure -text $msg
    }
}

proc SetFullScreenMode { win } {
    set sh [winfo screenheight $win]
    set sw [winfo screenwidth  $win]

    wm minsize $win $sw $sh
    wm maxsize $win $sw $sh
    set fmtStr [format "%dx%d+0+0" $sw $sh]
    wm geometry $win $fmtStr
    wm overrideredirect $win 1
    focus -force $win
}

proc SetWindowMode { win w h } {
    set sh [winfo screenheight $win]
    set sw [winfo screenwidth  $win]

    wm minsize $win 10 10
    wm maxsize $win $sw $sh
    set fmtStr [format "%dx%d+0+25" $w $h]
    wm geometry $win $fmtStr
    wm overrideredirect $win 0
    focus -force $win
}

# Toggle between windowing and fullscreen mode.
proc ToggleWindowMode {} {
    if { $::fullScreen } {
        SetFullScreenMode .
        set ::fullScreen false
    } else {
        SetWindowMode . $::gDemo(winWidth) $::gDemo(winHeight)
        set ::fullScreen true
    }
}

proc IncrRotSpeed { val } {
    set ::rotzSpeed [expr $::rotzSpeed + $val]
}

proc IncrNumDivs { val } {
    global patch

    set ::divs [expr $::divs + $val]
    if { $::divs < 1 } {
        set ::divs 1
    }
    set patch(dlBPatch) [genBezier $::divs]     ; # Update the patch
    .fr.toglwin postredisplay
}

proc ToggleShowPoints {} {
    set ::showCPoints [expr ! $::showCPoints]
    .fr.toglwin postredisplay
}

# Adds 2 points. Don't just use '+' ;)
proc pointAdd { p q } {
    set r [list 0.0 0.0 0.0]
    lset r 0 [expr {[lindex $p 0] + [lindex $q 0]}]
    lset r 1 [expr {[lindex $p 1] + [lindex $q 1]}]
    lset r 2 [expr {[lindex $p 2] + [lindex $q 2]}]
    return $r
}

# Multiplies a point and a constant. Don't just use '*'
proc pointTimes { c p } {
    set r [list 0.0 0.0 0.0]
    lset r 0 [expr {[lindex $p 0] * $c}]
    lset r 1 [expr {[lindex $p 1] * $c}]
    lset r 2 [expr {[lindex $p 2] * $c}]
    return $r
}

# Calculates 3rd degree polynomial based on 4 points
# and a single variable (u) which is generally between 0 and 1
proc Bernstein { u p0 p1 p2 p3 } {
    set a [pointTimes [expr pow($u,3)] $p0]
    set b [pointTimes [expr 3*pow($u,2)*(1-$u)] $p1]
    set c [pointTimes [expr 3*$u*pow((1-$u),2)] $p2]
    set d [pointTimes [expr pow((1-$u),3)] $p3]
    set r [pointAdd [pointAdd $a $b] [pointAdd $c $d]]

    return $r
}

# Generates a display list based on the data in the patch
# and the number of divisions
proc genBezier { divs } {
    global patch

    set u 0
    set v 0

    set drawlist [glGenLists 1]         ; # make the display list

    # get rid of any old display lists
    if { [info exists patch(dlBPatch)] } {
        glDeleteLists $patch(dlBPatch) 1
    }

    set temp0 $patch(anchors,0,3)     ; # the first derived curve (along x axis)
    set temp1 $patch(anchors,1,3)
    set temp2 $patch(anchors,2,3)
    set temp3 $patch(anchors,3,3)

    # create the first line of points
    for { set v 0 } { $v <= $divs } { incr v } {
        set px [expr double($v)/double($divs)] ; # percent along x axis
        # use the 4 points from the derives curve to calculate the points along that curve
        set last($v) [Bernstein $px $temp0 $temp1 $temp2 $temp3]
    }

    glNewList $drawlist GL_COMPILE              ; # Start a new display list
    glBindTexture GL_TEXTURE_2D [$patch(texture) get 0] ; # Bind the texture

    for { set u 1 } { $u <= $divs } { incr u } {
        set py [expr double($u)/double($divs)] ; # percent along y axis
        set pyold [expr (double($u)-1.0)/double($divs)]       ; # Percent along old Y axis

        # Calculate new bezier points
        set temp0 [Bernstein $py $patch(anchors,0,0) $patch(anchors,0,1) $patch(anchors,0,2) $patch(anchors,0,3)]
        set temp1 [Bernstein $py $patch(anchors,1,0) $patch(anchors,1,1) $patch(anchors,1,2) $patch(anchors,1,3)]
        set temp2 [Bernstein $py $patch(anchors,2,0) $patch(anchors,2,1) $patch(anchors,2,2) $patch(anchors,2,3)]
        set temp3 [Bernstein $py $patch(anchors,3,0) $patch(anchors,3,1) $patch(anchors,3,2) $patch(anchors,3,3)]

        glBegin GL_TRIANGLE_STRIP                       ; # Begin a new triangle strip

        for { set v 0 } { $v <= $divs } { incr v } {
            set px [expr double($v)/double($divs)] ; # percent along x axis

            glTexCoord2f $pyold $px                     ; # Apply the old texture coords
            glVertex3d [lindex $last($v) 0] \
                       [lindex $last($v) 1] \
                       [lindex $last($v) 2]             ; # Old Point

            # Generate new point
            set last($v) [Bernstein $px $temp0 $temp1 $temp2 $temp3]
            glTexCoord2f $py $px                        ; # Apply the new texture coords
            glVertex3d [lindex $last($v) 0] \
                       [lindex $last($v) 1] \
                       [lindex $last($v) 2]             ; # New Point
        }

        glEnd                                   ; # END the triangle srip
    }

    glEndList                                   ; # END the list

    return $drawlist                            ; # Return the display list
}

# set the bezier vertices
proc initBezier {} {
    global patch

    set patch(anchors,0,0) [list  -0.75 -0.75  -0.5]
    set patch(anchors,0,1) [list  -0.25 -0.75   0.0]
    set patch(anchors,0,2) [list   0.25 -0.75   0.0]
    set patch(anchors,0,3) [list   0.75 -0.75  -0.5]
    set patch(anchors,1,0) [list  -0.75 -0.25  -0.75]
    set patch(anchors,1,1) [list  -0.25 -0.25   0.5]
    set patch(anchors,1,2) [list   0.25 -0.25   0.5]
    set patch(anchors,1,3) [list   0.75 -0.25  -0.75]
    set patch(anchors,2,0) [list  -0.75  0.25   0.0]
    set patch(anchors,2,1) [list  -0.25  0.25  -0.5]
    set patch(anchors,2,2) [list   0.25  0.25  -0.5]
    set patch(anchors,2,3) [list   0.75  0.25   0.0]
    set patch(anchors,3,0) [list  -0.75  0.75  -0.5]
    set patch(anchors,3,1) [list  -0.25  0.75  -1.0]
    set patch(anchors,3,2) [list   0.25  0.75  -1.0]
    set patch(anchors,3,3) [list   0.75  0.75  -0.5]
}

proc LoadImage { imgName numChans } {
    if { $numChans != 3 && $numChans != 4 } {
        error "Error: Only 3 or 4 channels allowed ($numChans supplied)"
    }
    set texName [file join $::gDemo(scriptDir) "Data" $imgName]
    set retVal [catch {set phImg [image create photo -file $texName]} err1]
    if { $retVal != 0 } {
        error "Error reading image $texName ($err1)"
    } else {
        set w [image width  $phImg]
        set h [image height $phImg]
        set texImg [tcl3dVectorFromPhoto $phImg $numChans]
        image delete $phImg
    }
    return [list $texImg $w $h]
}

proc LoadGLTexture {} {
    global patch

    set imgInfo [LoadImage "NeHe.bmp" 3]
    set imgData   [lindex $imgInfo 0]
    set imgWidth  [lindex $imgInfo 1]
    set imgHeight [lindex $imgInfo 2]

    set patch(texture) [tcl3dVector GLuint 1]      ; # Storage For 1 Texture

    # Create The Textures
    glGenTextures 1 $patch(texture)
    glBindTexture GL_TEXTURE_2D [$patch(texture) get 0]
    glTexImage2D GL_TEXTURE_2D 0 3 $imgWidth $imgHeight \
                 0 GL_RGB GL_UNSIGNED_BYTE $imgData
    glTexParameteri GL_TEXTURE_2D GL_TEXTURE_MIN_FILTER $::GL_LINEAR
    glTexParameteri GL_TEXTURE_2D GL_TEXTURE_MAG_FILTER $::GL_LINEAR

    # Delete the image data vector.
    $imgData delete
}

# Resize And Initialize The GL Window
proc ReshapeCallback { toglwin { w -1 } { h -1 } } {
    set w [$toglwin width]
    set h [$toglwin height]

    glViewport 0 0 $w $h        ; # Reset The Current Viewport
    glMatrixMode GL_PROJECTION  ; # Select The Projection Matrix
    glLoadIdentity              ; # Reset The Projection Matrix

    # Calculate The Aspect Ratio Of The Window
    gluPerspective 45.0 [expr double($w)/double($h)] 0.1 100.0

    glMatrixMode GL_MODELVIEW   ; # Select The Modelview Matrix
    glLoadIdentity              ; # Reset The Modelview Matrix
    set ::gDemo(winWidth)  $w
    set ::gDemo(winHeight) $h
}

# All Setup For OpenGL Goes Here
proc CreateCallback { toglwin } {
    global patch

    glEnable GL_TEXTURE_2D                  ; # Enable Texture Mapping

    glShadeModel GL_SMOOTH                  ; # Enable Smooth Shading
    glClearColor 0.05 0.05 0.05 0.5         ; # Black Background
    glClearDepth 1.0                        ; # Depth Buffer Setup
    glEnable GL_DEPTH_TEST                  ; # Enables Depth Testing
    glDepthFunc GL_LEQUAL                   ; # The Type Of Depth Testing To Do
    glHint GL_PERSPECTIVE_CORRECTION_HINT GL_NICEST ; # Really Nice Perspective Calculations

    initBezier                              ; # Initialize the Bezier's control grid
    LoadGLTexture                           ; # Load the texture
    set patch(dlBPatch) [genBezier $::divs] ; # Generate the patch
}

# Here's Where We Do All The Drawing
proc DisplayCallback { toglwin } {
    global patch

    if { [info exists ::animateId] } {
        set ::rotz [expr $::rotz + $::rotzSpeed]
    }

    # Clear Screen And Depth Buffer
    glClear [expr $::GL_COLOR_BUFFER_BIT | $::GL_DEPTH_BUFFER_BIT] 


    # Viewport command is not really needed, but has been inserted for
    # Mac OSX. Presentation framework (Tk) does not send a reshape event,
    # when switching from one demo to another.
    glViewport 0 0 [$toglwin width] [$toglwin height]

    glLoadIdentity                      ; # Reset The Current Modelview Matrix
    glTranslatef 0.0 0.0 -4.0
    glRotatef -75.0 1.0 0.0 0.0
    glRotatef $::rotz 0.0 0.0 1.0       ; # Rotate The Triangle On The Z axis ( NEW )

    glCallList $patch(dlBPatch)         ; # Call the Bezier's display list

    # this need only be updated when the patch changes
    if { $::showCPoints } {
        glDisable GL_TEXTURE_2D
        glColor3f 1.0 0.0 0.0
        for { set i 0 } { $i < 4 } { incr i } {
            # draw the horizontal lines
            glBegin GL_LINE_STRIP
            for { set j 0 } { $j < 4 } { incr j } {
                glVertex3dv $patch(anchors,$i,$j)
            }
            glEnd
        }
        for { set i 0 } { $i < 4 } { incr i } {
            # draw the vertical lines
            glBegin GL_LINE_STRIP
            for { set j 0 } { $j < 4 } { incr j } {
                glVertex3dv $patch(anchors,$j,$i)
            }
            glEnd
        }
        glColor3f 1.0 1.0 1.0
        glEnable GL_TEXTURE_2D
    }
    $toglwin swapbuffers
}

proc Animate {} {
    .fr.toglwin postredisplay
    set ::animateId [tcl3dAfterIdle Animate]
}

proc StartAnimation {} {
    if { ! [info exists ::animateId] } {
        Animate
    }
}

proc StopAnimation {} {
    if { [info exists ::animateId] } {
        after cancel $::animateId 
        unset ::animateId
    }
}

# Put all exit related code here.
proc ExitProg {} {
    exit
}

# Create the OpenGL window and some Tk helper widgets.
proc CreateWindow {} {
    frame .fr
    pack .fr -expand 1 -fill both
    # Create Our OpenGL Window
    togl .fr.toglwin -width $::gDemo(winWidth) -height $::gDemo(winHeight) \
                     -swapinterval 1 \
                     -double true -depth true \
                     -createproc CreateCallback \
                     -reshapeproc ReshapeCallback \
                     -displayproc DisplayCallback 
    listbox .fr.usage -font $::listFont -height 6
    label   .fr.info
    grid .fr.toglwin -row 0 -column 0 -sticky news
    grid .fr.usage   -row 1 -column 0 -sticky news
    grid .fr.info    -row 2 -column 0 -sticky news
    grid rowconfigure .fr 0 -weight 1
    grid columnconfigure .fr 0 -weight 1
    wm title . "Tcl3D demo: David Nikdel & NeHe's Bezier Tutorial (Lesson 28)"

    # Watch For ESC Key And Quit Messages
    wm protocol . WM_DELETE_WINDOW "ExitProg"
    bind .  "ExitProg"
    bind .      "ToggleWindowMode"
    bind .   "IncrRotSpeed -0.05"
    bind .    "IncrRotSpeed  0.05"
    bind .      "IncrNumDivs  1"
    bind .    "IncrNumDivs -1"
    bind .       "ToggleShowPoints"

    bind .fr.toglwin <1> "StartAnimation"
    bind .fr.toglwin <2> "StopAnimation"
    bind .fr.toglwin <3> "StopAnimation"
    bind .fr.toglwin  "StopAnimation"

    .fr.usage insert end "Key-Escape     Exit"
    .fr.usage insert end "Key-F1         Toggle window mode"
    .fr.usage insert end "Key-Up|Down    Increase|Decrease resolution"
    .fr.usage insert end "Key-Left|Right Increase|Decrease rotation angle"
    .fr.usage insert end "Key-c          Toggle control point drawing"
    .fr.usage insert end "Mouse-L|MR     Start|Stop animation"

    .fr.usage configure -state disabled
}

CreateWindow
PrintInfo [format "Running on %s with a %s (OpenGL %s, Tcl %s)" \
           $tcl_platform(os) [glGetString GL_RENDERER] \
           [glGetString GL_VERSION] [info patchlevel]]
if { [file tail [info script]] == [file tail $::argv0] } {
    # If started directly from tclsh or wish, then start animation.
    update
    StartAnimation
}