Digital Art Zone

The first thing to note is, whoa, what happened to the color of the plane? It’s definitely more grey. Why? Also, look at what happened to the specular-esque shading on each of the primitives? It got smaller, or at least that’s what appears to happen.

Now one more for image for though: “01c IDL Direction 100 Sat 000 Con.jpg” which, predictably, is at 0% contrast.

So wow, okay, that’s pretty strange stuff! Honestly, I’m a bit lost at this point as to what’s going on… the plane got darker, all apparent specular response everywhere is gone and we can’t even really see the edges of the objects as they’re in shadow. How bizarre is that, eh?

So what happens when lower the contrast on an image in your image editor? Well, that’s really kind of hard to describe too isn’t it? We’re not affecting the luminosity, we’re not affecting the brightness, but we are, I don’t know how to say it really, perhaps everything that isn’t white and isn’t black moves closer to the middle. Pure white and pure black don’t seem to change, just the things in between. This again would have the affect of creating an HDRI map that had FAR more areas that would apparently emit light, but it would leave any area that was actually black alone so those would still be “dark” areas in the map… That’s my hypothesis anyway…

Map Controls: Mixing Experiments
To see what would happen… I mixed less the above settings.

We already know what 100% and 100% look like, as that was the first image we compared against… So what does 50/50 look like?

Well, here it is… 02b IDL Direct 050 Sat 050 Con.jpg

Now this is particularly an interesting one. There’s a very “soft” feel to everything. I rather like the effect and I could see potential uses for it perhaps with 75% contrast instead of 50%, and with soft shadows instead of directional shadows… I think it would make a very cool lighting effect where the primary light source was intended to be nearly omnipresent (think a cave with bio-luminescence or some such)...

So what does 0% and 0% look like?  Well, here it is: “02c IDL Direct 000 Sat 000 Con.jpg”

Personally, I can’t really see the difference between that and 100% saturation with 0% contrast. I think that the contrast setting is overwhelming the effect of the “grey scale” nature of the saturation setting and the net results and so close that at least my eyes can’t tell the difference.

Map Controls: Final Thoughts

So what did I learn about map controls? Well, even though I didn’t show it one thing I learned is that 0% Saturation and 0% Contrast is NOT the same as no Environment map. Smile

What else did I learn?
1) Reducing the Saturation of a map can increase the overall “luminosity” of the map. I don’t want to say brightness, because that’d be the intensity control… it makes more areas of the map be treated as light emitting.

2) Reducing the Contrast of the map, keeps “obvious light sources” and “obvious shadows” but pretty much softens the impact of the map as a whole.

That’s what I’ve taken away from all that anyway.

What can you infer from these results?  What did you learn?

Next we’ll go over the “non-quality” portions of the Ray Tracing section. Those being “Occlusion Strength” and “indirect Lighting Strength”... After that will be a brief discussion on the remaining parameters which are all related, in one way or another, to what we would call the “quality” settings.

Side-Track: Intensity vs. Contrast
Muon Quark asked: So I wonder what would happen if you turned down the intensity of the light and used 0% contrast. If you turned the intensity down far enough, would it make the objects appear to glow? And if you also used a high ambient setting on the object, would that help with the glow effect? I think I will have to experiment with that today.

My theory at this point: I believe you will lose the light “bounce” with a lower intensity thus reducing / removing the color bounce effect.

Testing showed:

Turning down the intensity of the light along with the contrast really took alot of light bounce out of the scene. First one was normal settings. 100% contrast and intensity on the ue light and no ambient settings for the sphere. I used Hyde Park with 5XHI settings.

Second one is with contrast and intensity of the light down to 50% and I added an ambient setting to the sphere of 50% using 255/255/255. It sorta made the sphere glow but turning down the contrast AND intensity of the light, you really lose a lot of bounce.

Raytrace Settings: Occlusion Strength

So, we know what occlusion is right? Remember that it is basically a way of determining how much light a surface receives. It’s calculated by projecting light (or bouncing it if you prefer) and seeing how much of that light makes it to the current camera.

So what do you think Occlusion Strength does?

My guess, is that the lower the Occlusion Strength the more closely UE2 will behave to being in Ambient Only mode. In other words, 0% Occlusion SHOULD be the same as Ambient Only mode. That is just a guess. So let’s find out, shall we?

For this experiment I’ve created several primitives, gave them colors in the diffuse channel, made sure their ambient channel strength was set to 0%. I also set their specular glossiness to 35%, specular color to pure white, and specular strength to 100%. Then I dramatically upped the quality of the UE2 rendering parameters because I wanted the occlusion and shadows to be ultra clear but we’ll cover that later. UE2 is set to IDL w/Directional Shadows Mode using the Park Environment map. I’ve rotated the Park Environment slightly as shown in the first capture (hint, unhide hidden parameters, unlock the scale, translation sliders on the UE2 Environment Sphere sub-prop and you can Scale / Move it as I’ve done so you can see where the HDRI map light source will be. Also make sure you rotate the main UE2 object not the Environment Sphere).

Okay, so here’s the render of the above scene with Occlusion Strength set to 100%. I’ve attempted to identify what each effect on the scene was going to be.

Now, the same scene with Occlusion Strength set to 0%...

Did you expect the Shadows to the “back left” of each object to disappear? I didn’t! I thought THAT was part of directional shadows, but no, that’s directional occlusion! We’ve also clearly lost our bounce colorations as well. You can see it is missing all over the white plane, but also as bounce on the torus by observing how large (or small) the shadow is.

Very interesting.

So it looks like this might be a good control to use if you find your “color bleed” is too strong, though I doubt one would ever take it to 0% like I have in the example above.

Raytrace Settings: IDL Strength

So I went on to test what IDL Strength does… My guess is that this time it removes bounce behavior from the light making the IDL Mode equivalent to the Occlusion Mode.

So again, we start with an IDL Directional Shadows mode (just like above)

Then we reduce the Indirect Light Strength to 0% and render….

Yup, look at that, all the color bleed is gone but we still have the directional occlusion / shadows. So just for kicks, I switched the mode to Directional w/Shadows, re-upped IDL strength to 100% and re-rendered.

I can’t tell the difference. Why?  Because Occlusion mode (as opposed to IDL Mode) doesn’t create the “color blending” that the IDL strength parameter is used to control.  So basically, IDL Mode with IDL Strength set to 0% is equivalent to Occlusion Mode.  I think I’ve nailed what that one does.  Again, I think this time you’d use it over reduced Occlusion to cut down color response but to keep the wonderful directional occlusion that looks so good.

Raytrace Settings: Occlusion Color

That brings us to one that should be fairly obvious, Occlusion Color. Since now we know what each UE2 mode does and how it creates occlusion (soft being “directionless” as opposed to the obvious “directional” modes), we can, reasonably expect, Occlusion Color to tint the “occlusion shadows” based on the color we pick. To be honest, I’ve never changed this value before. Smile Shadows are supposed to be black right?

Well, why might we want to do this? I can think of a few Sci-Fi / Magic effect reasons that might warrant it but what else? How about a fake glow? Cranking up the ambient will get you something that glows but doesn’t cast light… Well, if you set the Environment Mode to Soft Shadows and the Occlusion Color to the “color of the light” you’re going to get an extra layer of “fake” color added (as opposed to just bounce) that makes it look more like light is being cast.

So here’s a fiddly bit quicky test I did to see what would happen using the above theory. Ambient is set to 50% strength and the same red (255,0,0) as the diffuse color (and later the Occlusion Color).

So, here I’ve changed the Occlusion Color from 0,0,0 to 255,0,0 and re-rendered.

Not the most convincing “light source” but certainly an interesting effect!

So another thing you might do with it is change the Occlusion color to generate interesting / unusual shadow colors. Like those “SciFi” effects I mentioned earlier. Here’s I’ve taken the multi-primitive scene and changed the Occlusion Color to 255,0,128.

It’s most interesting to look at the results on the green cube since the colors there are more additive than the yellow, red or orange. Hopefully this gives you an idea of what you might accomplish.

Journey 03: Other Settings

Now lastly let’s talk quickly about the various other dials there are on UE2 (we won’t cover the hidden ones, just the normal ones).

Occlusion Samples - This is a quality knob, but NOT your number one quality knob. It determines how man times to sample colors around the current pixel. Much like Pixel Samples does on the advanced render tab. This helps create smooth color transitions. The “4x high quality” setting of 128 is really quite high enough for almost everything.

Shadow Bias - This works like Shadows Bias on any other light. It’s the distance, in centimeters to shift the shadows TOWARD the light source to prevent self-shadowing.

Shading Rate - THIS is the number one quality knob for UE2. This is functionally equivalent to the shading rate on the Advanced Render tab. In fact, it OVERRIDES the shading rate on the advance render tab at least as far as the Occlusion and Light generated by UE2 goes. The 4X Hi quality setting defaults to a value of 8. This generates the most complaints I see on the forums… “Even at 4x Hi the shadows are splotchy!”. This is because, as we discussed earlier in the thread that UE2 is best used as an auxiliary light and not as a stand alone light. For my “high quality” settings a few renders back, I lowered the shading rate to 1.00. You can see how much cleaner things look. Expect the same type of “render time” hit when adjusting the shading rate here. The default value of 8.00 is generally fine when using other lights with shadows.

Max Error - This is a quality knob. It’s also a very interesting one. I had to do some experimenting and some research to figure out what the heck this is. Basically, this is the 3Delight Irradiance Max Error value. It determines how strictly the irradiance (think strength of emitted light from a surface) is calculated. The short version is, higher values = lower quality = faster renders. When using UE2 with helper lights, it’s probably OK to raise this value up from the “4x Hi” value of 0.10.

Maximum trace Distance - This isn’t a quality knob but it has a HUUUUUGE effect on how occlusion is handled in the render. Basically this value is another “distance in centimeters” parameter. It measures the distance between surfaces to determine if occlusion occurs. So if you were, to say, set the maximum trace distance to 5 (centimeters) you’ll get a very small occlusion effect. The default value is 500 cm (roughly 16.4 feet btw). Lowering the value will also significantly decrease render times. It also makes UE2 useful as an indoor lighting effect. I tend to default to a value of 25 (roughly 1 foot) for indoor work.

Hope you found all of this useful.