Demo 11 of 68 in category RedBook
 |
# blendeqn.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.
#
# Demonstrate the different blending functions available with the
# OpenGL imaging subset. This program demonstrates use of the
# glBlendEquation call.
#
# The following keys change the selected blend equation function:
#
# 'a' -> GL_FUNC_ADD
# 's' -> GL_FUNC_SUBTRACT
# 'r' -> GL_FUNC_REVERSE_SUBTRACT
# 'm' -> GL_MIN
# 'x' -> GL_MAX
package require tcl3d
# 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 $msg
}
}
proc CreateCallback { toglwin } {
glClearColor 1.0 1.0 0.0 0.0
glBlendFunc GL_ONE GL_ONE
glEnable GL_BLEND
}
proc DisplayCallback { toglwin } {
glClear GL_COLOR_BUFFER_BIT
# Viewport command is not really needed, but has been inserted for
# Mac OSX. Presentation framework (Tk) does not send a reshape event,
# when switching from one demo to another.
glViewport 0 0 [$toglwin width] [$toglwin height]
glColor3f 0.0 0.0 1.0
glRectf -0.5 -0.5 0.5 0.5
glFlush
$toglwin swapbuffers
}
proc ReshapeCallback { toglwin { w -1 } { h -1 } } {
set w [$toglwin width]
set h [$toglwin height]
set aspect [expr double ($w) / double ($h)]
glViewport 0 0 $w $h
glMatrixMode GL_PROJECTION
glLoadIdentity
if {$aspect < 1.0} {
set aspect [expr 1.0 / $aspect]
glOrtho [expr -1.0 * $aspect] $aspect -1.0 1.0 -1.0 1.0
} else {
glOrtho -1.0 1.0 [expr -1.0 * $aspect] $aspect -1.0 1.0
}
glMatrixMode GL_MODELVIEW
}
proc UpdateMsg { msgStr } {
.fr.usage configure -state normal
.fr.usage delete end
.fr.usage insert end $msgStr
.fr.usage configure -state disabled
}
proc setBlendEquation { equat msgStr } {
$::glBlendEquationFunc $equat
UpdateMsg $msgStr
.fr.toglwin postredisplay
}
frame .fr
pack .fr -expand 1 -fill both
togl .fr.toglwin -width 512 -height 512 -double true \
-createcommand CreateCallback \
-reshapecommand ReshapeCallback \
-displaycommand DisplayCallback
listbox .fr.usage -font $::listFont -height 7
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 blendeqn"
set msg {"white square on yellow background"}
bind . <Key-a> "setBlendEquation $::GL_FUNC_ADD $msg"
set msg {"blue square on yellow background"}
bind . <Key-s> "setBlendEquation $::GL_FUNC_SUBTRACT $msg"
set msg {"yellow square on yellow background"}
bind . <Key-r> "setBlendEquation $::GL_FUNC_REVERSE_SUBTRACT $msg"
set msg {"black square on yellow background"}
bind . <Key-m> "setBlendEquation $::GL_MIN $msg"
set msg {"white square on yellow background"}
bind . <Key-x> "setBlendEquation $::GL_MAX $msg"
bind . <Key-Escape> "exit"
.fr.usage insert end "Key-a GL_FUNC_ADD"
.fr.usage insert end "Key-s GL_FUNC_SUBTRACT"
.fr.usage insert end "Key-r GL_FUNC_REVERSE_SUBTRACT"
.fr.usage insert end "Key-m GL_MIN"
.fr.usage insert end "Key-x GL_MAX"
.fr.usage insert end "Key-Escape Exit"
.fr.usage insert end "Default is GL_FUNC_ADD"
.fr.usage configure -state disabled
PrintInfo [tcl3dOglGetInfoString]
if { ! [tcl3dOglHaveVersion 1 2] } {
tk_messageBox -icon warning -type ok -title "Invalid OpenGL version" \
-message [format "Feature needs OpenGL >= 1.2. Only have %s" \
[glGetString GL_VERSION]]
}
set glBlendEquationFunc [tcl3dOglFindFunc "glBlendEquation"]
if { $glBlendEquationFunc eq "" } {
tk_messageBox -icon error -type ok -title "Missing OpenGL function" \
-message "OpenGL function glBlendEquation missing"
exit
}
|
