When you use frenzil the surfaces that are facing towards the camera are transparent whilst the surfaces facing sideways become opaque, i want to find a way that can reverse this and have it make and appropriate alpha reactive shadow and reflection.
By this i mean that i have tried different ways and something strange happens.
My attempts were on a sphere so that the desired result would look a bit like a standard halo.
First i tried using a blend texture, which affects alpha, and i mapped this with normals, it looks fine but in reflections the normals are reversed so reflection looks completely different.
My next attempt used nodes to flip the alpha on a sphere will frenzil effects on it, this produced a good effect and a good reflection but the shadow was wrong, in fact the shadow was unaffected by the nodes.
All other attempts were based on these two methods and had the same problems.
Without a .blend and/or a screenie this is kind of hit or miss. First off, the reflective pass is a bit unusual in that there is only ONE proper way to combine it because it contains both positive AND negative color values. This means that you need a mix node set to ADD in order to recombine it properly in the image. The positive values within the pass will add to the diffuse pass within the image while the negative values will subtract from the diffuse pass. If you want to reverse the effect then logic seems to dictate that you should set your mix node to SUBTRACT. As for the alpha values of which you write, I have absolutely no awareness of reflections or fresnel having any effect on alpha. If you want to reverse the alpha then you need to pump the alpha chamnnel through a color ramp and REVERSE the color bands from their default settings.
Pumping the reflective pass through a color ramp should convert it’s chroma values to luma values so inverting the color bands on this operation and using the resulting color output as the alpha input on a set alpha node may also be an avenue which you may wish to explore.
When Blender 2.42 was first introduced, someone on this site created a .pdf file to help newbies get started with the nodes. Whoever that person was, they hit the nail on the head when they wrote, “You need to learn to think like a pixel”. God bless 'em, whoever they were, because this 100% true. Ultimately, chroma and luma data is all that there is and learning the proper methods for combining each pass will speed you along your path to Blender compositing Nervana.
Some of it is in palin English and some of it is in programmer’s geek-speek. Continual reference to this page will eventually result in quite a good understanding of Blender’s compositor as you will slowly decipher the hidden meanings contained within some of the more abstract descriptions of the render passes. It can be a bit painful at times but it is totally worth it. That page is Blender’s compositing bible.
Sorry for not saying thanks, this has been a bit of fun experimenting for me and something i forgot about for a while, so thanks, but i couldn’t turn your advice into something that worked for me. I’ve never taken much time to understand the mechanics of how blender composits and renders.
I think this image will clear up what i am trying to do.
As you can see i flipped the alpha with colour ramp, tweaked with a RGB curve, now i need the same effect for the shadow.
And yes, frenzil does affect alpha, the alpha setting for this is at 1.
