bagginsbill opened this issue on Apr 23, 2008 ยท 2832 posts
bagginsbill posted Wed, 28 May 2008 at 8:26 PM
Cobaltdream has it right. You get to combine the individual render passes using some other tool, where you can adjust the brightness of each pass (or the darkness of the shadow/AO pass) one-by-one without re-rendering.
I experimented with this technique a while ago. I even built my own tool to combine the passes in interesting ways, because it's a bit tedious to do in photoshop or similar programs. A purpose-built program to combine the separate render passes makes things easier. Particularly, what you want to do that is missing from photoshop is to select some subset of the passes and raise or lower their brightess together, or do the opposite, where you choose a layer or group of layers and raise or lower its "weight", simultaneously doing the opposite to all the others.
However, I do a lot of work with reflection and the separate reflections never seemed to combine nicely. I now understand (doh) that the problem was that I was combining the layers linearly, when what I needed to do was gamma correct the combination. Reflections, being of necessity relatively low in brightness, really need to be gamma corrected in order to keep the correct visual relationship to the other elements in the scene.
Because I was never satisfied with the results, I abandoned the separate-passes technique, preferring to get the render closer to correct in the first place.
Looking back over all I've done, I see now that over and over I was fighting with visual flaws that were entirely because the way my screen showed me the final product was not accurate, even though the math, up to that point, was correct.
I don't think that Photoshop can correctly perform the assembly of separate passes into a gamma corrected whole interactively.
Perhaps I should resurrect and finish the tool I was building and put it out for everybody to use.
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)