foligatto

I guess I wasn't as clear about my problem as I had originally thought. I was trying to use the alpha value in the color POP to drive the opacity of the shader I'm applying to metaballs in my scene. It appears that $LIFE was being read fine by the color POP. The problem was that only a single value was being passed to the opacity channel of the SHOP rather than a different value for each point/particle, or so it seems.

I'm not sure that I fully understand the problem, and I found a workaround using a point POP with a point() function calling the life of the particles. I just wondered if someone could help me understand what I clearly don't grasp quite yet: the rules in Houdini for passing data from one network to the other.

I would really appreciate a good explanation of this aspect of houdini, or perhaps just pointing me to a good reference that explains it well.

Thanks

Can someone help me make sense of how and where certain variables are accessible in Houdini?

I was recently trying to increase transparency of a particle as it neared death, and I found that I couldn't access the $LIFE variable in the color POP, from which I wanted to pass over the alpha channel into the SHOP. I couldn't get the poppoint() function to access this variable either. I ended up having to use a point() function in a point SOP to alter the alpha channel from there.

Could someone help me understand why the original approach of accessing the $LIFE variable from a color POP to pass to the shader wasn't working? Is the point SOP really the only way to go about increasing transparency with a particle's age?

Thanks

That worked great. I didn't understand that I had to use the profile sop in conjunction with the surfsect sop.

thanks much