A little problem I solved, that others might have. I was trying to set the alpha of an object:
cloudTexture = viz.addTexture('pink4.png')
cloud = viz.addTexQuad()
cloud.setPosition(0,0,0)
cloud.texture(cloudTexture)
cloud.alpha(0.5)
This doesn't seem possible. The solution (for me) was to use an image that doesn't have alpha information, i.e. convert pink4.png to pink4.jpg. It then works
Mike.