16-bit vs. 32-bit vs. 32-bit 2X Lightmaps

LarryG on 27/9/2012 at 17:52

Can someone explain to me just what these options really mean? In the past I only worried about Quick Lighting vs. Raycast Lighting vs. Objcast, and I know that Quick was for a quick and dirty look-see and Objcast was for true game release lighting, and I had no idea about Raycast so I ignored it. Those are still there and I will treat them the same (though considering how fast the lighting pass is now, I may use Objcast most of the time). But now we have these other options and I don't really know what is best. I figure 32-bit is twice the resolution (more or less) than 16-bit. So why would I ever want 16-bit now? And there are two flavors of 32-bit. What's with that? Is one better than another? Should I use 16-bit up until I'm getting ready for beta tests and then switch to 32-bit (either one), or what?

DrK on 27/9/2012 at 18:00

Quote Posted by LarryG

...Objcast was for true game release lighting, and I had no idea about Raycast so I ignored it.

Just for info, Raycast is the same than Objcast, except objects shadows are ignored in the calculation. So it still gives a good idea about the real lightings in your mission, and works way faster.

Otherwise, I'd like to know as well. Maybe 32-bit allows much sharper shadows on textures ?

Yandros on 27/9/2012 at 18:20

I would think 32-bit gives you better shadows, and also no banding in the light radius where it hits terrain. If you look at The Watcher's comparison shots in the other thread, the old shot clearly shows banding rings on the wall around the light, whereas it's a smooth gradient in 1.19 (with presumably 32-bit lighting). I don't see a reason ever to use 16-bit again.

ZylonBane on 27/9/2012 at 18:23

Vanilla Thief II/SS2 lightmaps use 16-bit color, most likely RGB565. This is why they're so infamously prone to weird banding artifacts, since they have such low luminance resolution. Based on the posted screenshots, the 32-bit lighting option almost certainly bumps the lightmap resolution up to at least 8 bits per color channel, resulting in much smoother brightness transitions. It seems unlikely that lightmap spatial resolution has gone up any-- that would result in massive increases to file size.

Yandros on 27/9/2012 at 18:26

Quote Posted by ZylonBane

It seems unlikely that lightmap spatial resolution has gone up any-- that would result in massive increases to file size.

If I understand this correctly, that means that shadow resolution is not increased, correct?

ZylonBane on 27/9/2012 at 18:39

Beats me, I haven't tried messing around in the new DromEd yet. It just seems unlikely. Have any controls for lightmap density been added? If not, then lightmap resolution is probably still the same.

Yandros on 27/9/2012 at 19:11

I haven't seen any. I guess I was asking, assuming the resolution hasn't changed, that means shadows are no finer than they were before. Not that I knew for sure if that was the case.

Angs on 27/9/2012 at 19:52

Hi, I've been asking myself the same question all day and decided to try it out myself. (First post btw, hello!) Guessing from the names, the 16/32-bit part means bit depth, i.e. more range per pixel. With 32 bits you get less quantization artifacts (banding). I guess the 2X part means twice the resolution in one dimension. If this is the case, the difference between 32-bit vs 32-bit 2X is a 4-fold increase in lightmap sizes.

I took some bad screenshots from my experiments (16-bit vs 32bit 2X): (http://imgur.com/a/ecGgM) http://imgur.com/a/ecGgM. In the first image pair the banding around the lampposts disappears when using 32bit2X. From the other you can see that the 32-bit lightmaps probably have more range in the bright end.

By the way, does anyone know how the original missions could be updated to use the new lightmaps? I'm amazed I could even do this much, couldn't even figure how to make dromed save a mission and these were the only missions it would even let me edit..

LarryG on 27/9/2012 at 22:17

Found (http://www.yougamers.com/hardware/dictionary/1/) this. Particularly,

Quote:

Contrary to popular belief, it is not about how many colours the bits give you (although this does have some importance). The reason is about colour gradients: imagine a scene that is nothing but blue. The top of the scene is very pale and the hue deepens as you go further down the screen. The number of bits per channel restricts the number of steps that can be used in this colour gradient. 5-bit channels only give you 32 steps, making the gradient very banded. 8-bit channels are better with 256 steps but once you start going higher than 10-bits, the gradient steps become much finer.

If I understand this correctly :sweat: it supports what ZB was saying:thumb:, that 32-bit lightmaps reduces color banding by giving you light intensity gradation. :cool: But what about 32-bit vs. 32-bit 2X? I found some hints that it might have to do with diffuse lighting or 2 times over-brightening (I assume this means higher contrast? darker darks and brighter brights?), but no site that really defines it in any way that I can understand. :confused: I guess I can just try both and see which effect I like better for each of my missions' atmosphere/mood over all.

Edit: See (http://www.ttlg.com/forums/showthread.php?t=140086&page=4&p=2144160&viewfull=1#post2144160) Sensut's post for screen shot comparisons. I can't see a need for 2X in the Thief world. That seems awfully extreme ...

blaydes99 on 28/9/2012 at 04:13

Angs, from what I can tell in your examples, 2X seems to put a kind of HDR-style overbrightening effect instead of an increase in resolution (this goes with what you are saying LarryG). Seems to make the lights more "potent".