Demo 42 of 68 in category RedBook
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# pickdepth.tcl
#
# An example of the OpenGL red book modified to work with Tcl3D.
# The original C sources are Copyright (c) 1993-2003, Silicon Graphics, Inc.
# The Tcl3D sources are Copyright (c) 2005-2022, Paul Obermeier.
# See file LICENSE for complete license information.
#
# Picking is demonstrated in this program. In
# rendering mode, three overlapping rectangles are
# drawn. When the left mouse button is pressed,
# selection mode is entered with the picking matrix.
# Rectangles which are drawn under the cursor position
# are "picked." Pay special attention to the depth
# value range, which is returned.
package require tcl3d
tcl3dConsoleCreate .tcl3dOutputConsole "# " "Pickdepth Output"
set BUFSIZE 512
set selectBuffer [tcl3dVector GLuint $::BUFSIZE]
# Font to be used in the Tk listbox.
set listFont {-family {Courier} -size 10}
# Show errors occuring in the Togl callbacks.
proc bgerror { msg } {
tk_messageBox -icon error -type ok -message "Error: $msg\n\n$::errorInfo"
exit
}
# 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 CreateCallback { toglwin } {
glClearColor 0.0 0.0 0.0 0.0
glEnable GL_DEPTH_TEST
glShadeModel GL_FLAT
glDepthRange 0.0 1.0 ; # The default z mapping
}
# The three rectangles are drawn. In selection mode,
# each rectangle is given the same name. Note that
# each rectangle is drawn with a different z value.
#
proc drawRects { mode } {
if { $mode == $::GL_SELECT } {
glLoadName 1
}
glBegin GL_QUADS
glColor3f 1.0 1.0 0.0
glVertex3i 2 0 0
glVertex3i 2 6 0
glVertex3i 6 6 0
glVertex3i 6 0 0
glEnd
if { $mode == $::GL_SELECT } {
glLoadName 2
}
glBegin GL_QUADS
glColor3f 0.0 1.0 1.0
glVertex3i 3 2 -1
glVertex3i 3 8 -1
glVertex3i 8 8 -1
glVertex3i 8 2 -1
glEnd
if { $mode == $::GL_SELECT } {
glLoadName 3
}
glBegin GL_QUADS
glColor3f 1.0 0.0 1.0
glVertex3i 0 2 -2
glVertex3i 0 7 -2
glVertex3i 5 7 -2
glVertex3i 5 2 -2
glEnd
}
# processHits() prints out the contents of the
# selection array.
#
proc processHits { hits } {
set count 0
puts "hits = $hits"
for { set i 0 } { $i < $hits } { incr i } {
set names [$::selectBuffer get $count]
puts " number of names for hit = $names"
incr count
puts -nonewline [format " z1 is %g;" \
[expr double ([$::selectBuffer get $count]) / 0x7fffffff]]
incr count
puts [format " z2 is %g" \
[expr double ([$::selectBuffer get $count]) / 0x7fffffff]]
incr count
puts -nonewline " the name is "
for { set j 0 } { $j < $names } { incr j } {
puts -nonewline [format "%d " [$::selectBuffer get $count]]
incr count
}
puts ""
}
}
# pickRects() sets up selection mode, name stack,
# and projection matrix for picking. Then the objects
# are drawn.
#
proc pickRects { x y } {
set viewport [tcl3dVector GLint 4]
glGetIntegerv GL_VIEWPORT $viewport
glSelectBuffer $::BUFSIZE $::selectBuffer
glRenderMode GL_SELECT
glInitNames
glPushName 0
glMatrixMode GL_PROJECTION
glPushMatrix
glLoadIdentity
# create 5x5 pixel picking region near cursor location
gluPickMatrix $x [expr [$viewport get 3] - $y] 5.0 5.0 $viewport
glOrtho 0.0 8.0 0.0 8.0 -0.5 2.5
drawRects $::GL_SELECT
glPopMatrix
glFlush
set hits [glRenderMode GL_RENDER]
$viewport delete
processHits $hits
}
proc DisplayCallback { toglwin } {
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]
drawRects $::GL_RENDER
glFlush
$toglwin swapbuffers
}
proc ReshapeCallback { toglwin { w -1 } { h -1 } } {
set w [$toglwin width]
set h [$toglwin height]
glViewport 0 0 $w $h
glMatrixMode GL_PROJECTION
glLoadIdentity
glOrtho 0.0 8.0 0.0 8.0 -0.5 2.5
glMatrixMode GL_MODELVIEW
glLoadIdentity
}
frame .fr
pack .fr -expand 1 -fill both
togl .fr.toglwin -width 400 -height 400 -double true -depth true \
-createcommand CreateCallback \
-reshapecommand ReshapeCallback \
-displaycommand DisplayCallback
listbox .fr.usage -font $::listFont -height 2
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: OpenGL Red Book example pickdepth"
bind . <Key-Escape> "exit"
bind .fr.toglwin <1> "pickRects %x %y"
.fr.usage insert end "Key-Escape Exit"
.fr.usage insert end "Mouse-L Get pick results"
.fr.usage configure -state disabled
PrintInfo [tcl3dOglGetInfoString]
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