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View Full Version : GI and Image World / Surfaces seem to become 'reflective' -???



jeric_synergy
06-08-2015, 07:37 PM
I'm following an old Larry Shultz, RIP, tutorial and using Image World to get a wrap-around illumination.

I'm baffled by: my scene has a matte white 'cove' that completely blocks the background, but when I turn off the lights and illuminate the scene solely with Image World, the matte cove (which is like a flat-bottomed bowl) seems to become sort of reflective, in that I'm seeing the IWorld image, extremely vaguely.

Why is this? I'd think with a non-reflective cove I wouldn't see ANYTHING, just illumination. Am I misunderstanding what Image World +GI is doing?

spherical
06-09-2015, 01:11 AM
Screen grab???

jeric_synergy
06-09-2015, 01:23 AM
I think maybe it's just sorta the geometry interacting with the virtual sphere of imagery. IOW, the angles. :(

128571

spherical
06-09-2015, 01:56 AM
Ok, thanks for the screen grab, but it doesn't tell me anything pertinent. Looking at that one image makes things more confusing. What would help is one or two or more that show the relationship of all of the parts in the scene. IOW, where the 'cove' is, how big it is, where the objects inside (if they are inside it) are in relation to it, etc.

jeric_synergy
06-09-2015, 08:31 AM
Yeah... I think it's pilot error and simply not 'getting' how much IWorld will tint a surface.

Here's the scene: the effect is prominent when you PITCH the IWorld image, and turn off all other illumination.

128573

MSherak
06-09-2015, 12:30 PM
Yeah... I think it's pilot error and simply not 'getting' how much IWorld will tint a surface.

Here's the scene: the effect is prominent when you PITCH the IWorld image, and turn off all other illumination.

128573

Looking over this scene everything seems to be working correct. Have to remember that there are a couple levels of EV in the image..

jeric_synergy
06-09-2015, 03:23 PM
Now, this IS embarrassing.... "EV"?

Exposure Value???

MSherak
06-09-2015, 05:41 PM
Now, this IS embarrassing.... "EV"?

Exposure Value???

:) Yup. That kitchen pic has a range of -16.0ev to about +3.6ev before whiting out. A good center EV for this image would be in the -2.4ev to -2.6ev range which Image World already selects.. Make sure you turn on sRGB for the scene and set the image to linear. Then you can turn the brightness to 100% and get the color and not a blown out white when the lights are off..

JoePoe
06-09-2015, 07:07 PM
I did that and can't get anywhere near 100%. BUT... what I did do was open up the angle of the Cove wall, so I guess that let's in a lot more light.

I'm at 42% image world, 270 pitch.... and tweaked the surfacing a bit too.... 128579

new cove geo..... 128580

Edit side note: I'm having a heck of a time trying to get the stem to be anything other than almost total black....

oh... and your camera aspect ratio was set to ~1.2 which freaked me out for a good few minutes...

jeric_synergy
06-09-2015, 08:33 PM
Edit side note: I'm having a heck of a time trying to get the stem to be anything other than almost total black....
Huh, hadn't really surfaced that yet, I wonder what's the problem. Is it maybe inside-out?

Good point on the cove geometry, Joe: usually I make only half a cyc, but I got lazy....Hmmm, but it IS only single-sided.... anyway, many things wrong w/this scene, take heart noobies! I'm like a cautionary tale or something.

Still surprised by the amount of blue on the cove, but given the image I guess it makes perfect sense. How does Image World differ from using a .... oh wait, does it extend around the scene totally, unlike a spherical reflection? That is: why is Image World superior (or not) to other techniques?

jeric_synergy
06-09-2015, 08:45 PM
I'm at 42% image world, 270 pitch.... and tweaked the surfacing a bit too.... 128579

Harumph: also the water geo, you bastahhhhhd! ;)

In the LWS I posted, something about the reflection settings makes the apple appear to have a muffin-top. Don't know what's up with that.

JoePoe
06-09-2015, 08:57 PM
Superior? Don't know 'bout that. It's about what works right? Just gotta find the sweet spot.

Only thing I changed was pitch now =0 ..... 128581

... now bumping up to 100% brightness .... 128582.... BIG differences.

Image world etc is an image (made up of colors usually) as a light. So for all intents and purposes it's like having an array/multiple native lights with color instead of white, so yeah.... it's going to throw hues onto surfaces. Sometimes a lot.

Edit.... ahh yeah the water. But that's nothing, just a couple drops. Not what we're talking' 'bout here.

Edit2: Pitch still at 0, image set to Saturation=-1, and Image world brightness 75%. 128585

SpawnSP
06-19-2015, 02:49 AM
What happens if you increase the ray recursion limit?
Maybe the problem is when rays reach the limit, it falls back to the background image.