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#! /usr/bin/env python
from OpenGLContext import testingcontext
BaseContext = testingcontext.getInteractive()
from OpenGLContext import interactivecontext, drawcube
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.constants import GLfloat_3,GLfloat_4
import time
try:
from PIL.Image import open
except ImportError, err:
from Image import open
class TestContext( BaseContext ):
"""Blending modes demonstration"""
usage ="""Demonstrates blending functions:
press 'b' to toggle blending functions
press 'f' to toggle filter functions
press 'l' to toggle lighting
press '<pageup>' to speed up rotation
press '<pagedown>' to slow down rotation
"""
initialPosition = (0,0,2)
def OnInit( self ):
"""Load the image on initial load of the application"""
self.imageIDs = self.loadImages()
self.currentFilter = 0 # index into imageIDs
self.lightsOn = 0 # boolean
self.blendOn = 1
self.currentZOffset = -6
self.rotationCycle = 8.0
# note that these are different bindings from the tutorial,
# as you can wander around with the arrow keys already...
self.addEventHandler(
'keypress', name = 'f', function = self.OnFilter
)
self.addEventHandler(
'keypress', name = 'l', function = self.OnLightToggle
)
self.addEventHandler(
'keyboard', name = '<pageup>', function = self.OnSpeedUp,
state=0,
)
self.addEventHandler(
'keyboard', name = '<pagedown>', function = self.OnSlowDown,
state=0,
)
Our first change from the NeHe7 tutorial code, and the
only one in OnInit is to bind a handler for changing the blending
functions.
self.addEventHandler(
'keypress', name = 'b', function = self.OnBlendToggle
)
print self.usage
The Lights setup and the Lights method are identical to
the code from the NeHe7 translation
glLightfv( GL_LIGHT1, GL_AMBIENT, GLfloat_4(0.2, .2, .2, 1.0) );
glLightfv(GL_LIGHT1, GL_DIFFUSE, GLfloat_3(.8,.8,.8));
glLightfv(GL_LIGHT1, GL_POSITION, GLfloat_4(-2,0,3,1) );
def Lights (self, mode = 0):
Setup the global lights for your scene
if self.lightsOn:
glEnable( GL_LIGHTING )
glEnable(GL_LIGHT1);
glDisable(GL_LIGHT0);
else:
glDisable( GL_LIGHTING )
glDisable(GL_LIGHT1);
glDisable(GL_LIGHT0);
New customization point: Background
Background, like Lights is called by the default
RenderMode.SetupBindables method. It is used here
because the blending mode used by the tutorial
will not work unless the background is black.
def Background( self, mode):
"""Demo's use of GL_ONE assumes that background is black"""
if mode.passCount == 0:
glClearColor(0,0,0,0)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT )
def Render( self, mode):
BaseContext.Render( self, mode )
glTranslatef(1.5,0.0,self.currentZOffset);
We don't want to filter out back-facing faces
glDisable( GL_CULL_FACE )
glRotated(
time.time()%(self.rotationCycle)/self.rotationCycle * -360,
1,0,0
)
self.blend()
glEnable(GL_TEXTURE_2D)
Re-select our texture, could use other generated textures
if we had generated them earlier...
glBindTexture(GL_TEXTURE_2D, self.imageIDs[self.currentFilter])
self.drawCube()
glDisable(GL_TEXTURE_2D)
There are multiple blending mechanisms that could be used, the
original tutorial uses the first value declared here. The second
is what you would use to render back-to-front-sorted triangles to
appear transluscent. The third is just to show the effect.
BLENDSTYLES = [
(),
(GL_SRC_ALPHA, GL_ONE),
(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA),
(GL_SRC_ALPHA, GL_DST_ALPHA),
]
def blend( self ):
"""Choose and enable blending mode"""
if self.blendOn == 0:
glDisable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
glDepthMask( ~0 )
else:
glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glBlendFunc( * self.BLENDSTYLES[ self.blendOn] )
glDepthMask( 0 ) # prevent updates to the depth buffer...
The rest of the tutorial matches the NeHe7 translation.
def loadImages( self, imageName = "nehe_glass.bmp" ):
"""Load an image from a file using PIL,
produces 3 textures to demo filter types
"""
im = open(imageName)
try:
ix, iy, image = im.size[0], im.size[1], im.tostring("raw", "RGBA", 0, -1)
except SystemError:
ix, iy, image = im.size[0], im.size[1], im.tostring("raw", "RGBX", 0, -1)
IDs = []
# a Nearest-filtered texture...
ID = glGenTextures(1)
IDs.append( ID )
glBindTexture(GL_TEXTURE_2D, ID)
glPixelStorei(GL_UNPACK_ALIGNMENT,1)
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
glTexImage2D(GL_TEXTURE_2D, 0, 3, ix, iy, 0, GL_RGBA, GL_UNSIGNED_BYTE, image)
# linear-filtered
ID = glGenTextures(1)
IDs.append( ID )
glBindTexture(GL_TEXTURE_2D, ID)
glPixelStorei(GL_UNPACK_ALIGNMENT,1)
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR)
glTexImage2D(GL_TEXTURE_2D, 0, 3, ix, iy, 0, GL_RGBA, GL_UNSIGNED_BYTE, image)
# linear + mip-mapping
ID = glGenTextures(1)
IDs.append( ID )
glBindTexture(GL_TEXTURE_2D, ID)
glPixelStorei(GL_UNPACK_ALIGNMENT,1)
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST)
gluBuild2DMipmaps(GL_TEXTURE_2D, 3, ix, iy, GL_RGBA, GL_UNSIGNED_BYTE, image)
return IDs
def OnIdle( self, ):
self.triggerRedraw(1)
return 1
def OnBlendToggle( self, event ):
self.blendOn = (self.blendOn + 1)%len( self.BLENDSTYLES )
print 'Blend now %s, %s'% [
("None", "None"),
("GL_SRC_ALPHA", "GL_ONE"),
("GL_SRC_ALPHA", "GL_ONE_MINUS_SRC_ALPHA"),
("GL_SRC_ALPHA", "GL_DST_ALPHA"),
][ self.blendOn ]
def OnFilter( self, event):
"""Handles the key event telling us to change the filter"""
self.currentFilter = (self.currentFilter + 1 ) % 3
print 'Drawing filter now %s'% ( ["Nearest","Linear","Linear Mip-Mapped"][ self.currentFilter])
def OnLightToggle( self, event ):
"""Handles the key event telling us to toggle the lighting"""
self.lightsOn = not self.lightsOn
print "Lights now %s"% (["off", "on"][self.lightsOn])
def OnSpeedUp( self, event):
"""Handles key event to speed up"""
print 'speed up'
self.rotationCycle = self.rotationCycle /2.0
def OnSlowDown( self, event ):
"""Handles key event to slowdown"""
print 'slow down'
self.rotationCycle = self.rotationCycle * 2.0
def drawCube( self ):
"Draw a cube with both normals and texture coordinates"
glBegin(GL_QUADS);
glNormal3f( 0.0, 0.0, 1.0)
glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, 1.0);
glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, -1.0, 1.0);
glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, 1.0, 1.0);
glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, 1.0);
glNormal3f( 0.0, 0.0,-1.0);
glTexCoord2f(1.0, 0.0); glVertex3f(-1.0, -1.0, -1.0);
glTexCoord2f(1.0, 1.0); glVertex3f(-1.0, 1.0, -1.0);
glTexCoord2f(0.0, 1.0); glVertex3f( 1.0, 1.0, -1.0);
glTexCoord2f(0.0, 0.0); glVertex3f( 1.0, -1.0, -1.0);
glNormal3f( 0.0, 1.0, 0.0)
glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, -1.0);
glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, 1.0, 1.0);
glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, 1.0, 1.0);
glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, 1.0, -1.0);
glNormal3f( 0.0,-1.0, 0.0)
glTexCoord2f(1.0, 1.0); glVertex3f(-1.0, -1.0, -1.0);
glTexCoord2f(0.0, 1.0); glVertex3f( 1.0, -1.0, -1.0);
glTexCoord2f(0.0, 0.0); glVertex3f( 1.0, -1.0, 1.0);
glTexCoord2f(1.0, 0.0); glVertex3f(-1.0, -1.0, 1.0);
glNormal3f( 1.0, 0.0, 0.0)
glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, -1.0, -1.0);
glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, 1.0, -1.0);
glTexCoord2f(0.0, 1.0); glVertex3f( 1.0, 1.0, 1.0);
glTexCoord2f(0.0, 0.0); glVertex3f( 1.0, -1.0, 1.0);
glNormal3f(-1.0, 0.0, 0.0)
glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, -1.0);
glTexCoord2f(1.0, 0.0); glVertex3f(-1.0, -1.0, 1.0);
glTexCoord2f(1.0, 1.0); glVertex3f(-1.0, 1.0, 1.0);
glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, -1.0);
glEnd()
if __name__ == "__main__":
TestContext.ContextMainLoop()
Author:
Jeff Molofee (aka NeHe)
Author:
Tom Stanis
COPYRIGHT AND DISCLAIMER: (c)2000 Jeff Molofee / Tom Stanis
If you plan to put this program on your web page or a cdrom of
any sort, let me know via email, I'm curious to see where
it ends up :)
If you use the code for your own projects please give me
credit, or mention my web site somewhere in your program
or it's docs.
This code-walkthrough tutorial is generated from the nehe8.py script in the
OpenGLContext source distribution.
| OpenGLContext Python tutorials | ||
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| Previous | NeHe Translations: Blending Modes (NeHe 8) | Next |
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Blending Modes (NeHe 8)