[PyOpenGL-Users] Re: textures with transparency

[FvW <vw...@vu...>]

Hello,

I found the answer. The problem was my (mis)understanding of "blending". 
Attached is some working code. 

N.B. It is not meant to be nice code.

Best,
Fulko


from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
from Image import *

ESCAPE = '\033'

window = 0

xrot = yrot = zrot = 0.0

texture = 0

def LoadTextures():
    image = open("BlueFace.png")
    print image.format, image.size, image.mode

    ix = image.size[0]
    iy = image.size[1]
    image = image.tostring("raw", "RGBA", 0, -1)
	
    glPixelStorei(GL_UNPACK_ALIGNMENT,1)
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ix, iy, 0, GL_RGBA, GL_UNSIGNED_BYTE, image)
    
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE)
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    glEnable(GL_BLEND)
    glEnable(GL_CULL_FACE)



def InitGL(Width, Height):
    LoadTextures()
    glEnable(GL_TEXTURE_2D)
    glClearColor(0.0, 0.0, 0.0, 0.0)
    glClearDepth(1.0)
    glDepthFunc(GL_LEQUAL)
    glEnable(GL_DEPTH_TEST)
    glShadeModel(GL_SMOOTH)
	
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(45.0, float(Width)/float(Height), 0.1, 100.0)

    glMatrixMode(GL_MODELVIEW)


def ReSizeGLScene(Width, Height):
    if Height == 0:
	    Height = 1

    glViewport(0, 0, Width, Height)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(45.0, float(Width)/float(Height), 0.1, 100.0)
    glMatrixMode(GL_MODELVIEW)


def DrawGLScene():
	global xrot, yrot, zrot, texture

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
	glLoadIdentity()

        glPushMatrix()
	glBegin(GL_QUADS)			    
	
	glTexCoord2f(0.0, 0.0); glVertex3f(-5.0, -5.0,  -10.0)	
	glTexCoord2f(1.0, 0.0); glVertex3f( 5.0, -5.0,  -10.0)	
	glTexCoord2f(1.0, 1.0); glVertex3f( 5.0,  5.0,  -10.0)	
	glTexCoord2f(0.0, 1.0); glVertex3f(-5.0,  5.0,  -10.0)	
	
        glEnd();                                
	glPopMatrix()
		
        glPushMatrix()
	glTranslatef(0.0,0.0,-5.0)

	glRotatef(xrot,1.0,0.0,0.0)			
	glRotatef(yrot,0.0,1.0,0.0)			
	glRotatef(zrot,0.0,0.0,1.0)			

	glBegin(GL_QUADS)			    
	
	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)	
	
	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)	
	
	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)	
	
	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)	
	
	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)	
	
	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();				
        glPopMatrix()
  
	xrot  = xrot + 0.02                
	yrot = yrot + 0.02                 
	zrot = zrot + 0.02                 

	glutSwapBuffers()


def keyPressed(*args):
    if args[0] == ESCAPE:
	    glutDestroyWindow(window)
	    sys.exit()

def main():
	global window
	glutInit(sys.argv)
	glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH)
	glutInitWindowSize(640, 480)
	glutInitWindowPosition(0, 0)
        window = glutCreateWindow("Transparency Test")
        glutDisplayFunc(DrawGLScene)
        glutIdleFunc(DrawGLScene)
        glutReshapeFunc(ReSizeGLScene)
        glutKeyboardFunc(keyPressed)
        InitGL(640, 480)
        glutMainLoop()


print "Hit ESC key to quit."
main()