[flow_default] Transcription: 01 - What is GI.json

transcriptions/01 - What is GI.json

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+{
+  "audio_file": "01 - What is GI.wav",
+  "text": "How light works in reality is that it's cast out from its source, hits the subject, and then bounces many, many times. In 3D though, when you have a light like an area light, what it's actually doing is just casting light rays out, and it's hitting the object, and no bouncing is occurring at all. So to be able to have that realistic bouncing and scattering of light and dispersion of light that happens in reality, what 3D has to reenact that is called global illumination or GI. And while it makes your render look more realistic, it also increases your render time. So it's kind of similar to ambient occlusion or AO that adds that realistic shading that occurs in real life or shadowing that occurs in real life that also increases that lighting that much further though, but it really helps to have a good foundation to actually have a well lit scene. So how you can add GI to your scene is through your render settings right here. So I'll click on the little button with the clapper and the gear and here now watch what happens as this render kind of does its thing. You're gonna see that. So let's go to the effect menu here. Let's go to the effect menu here. Let's go to the effect menu here. Let, so let me turn off gi You're gonna see how dark our scene gets and if I turn the gi back on It's gonna do its calculation again, and it's gonna make our scene look that much brighter. And the reason for that is, is that with GI activated, our lights casting out from the light sources and it's bouncing one time. Okay. And what's actually controlling the bouncing are these two settings right here. So primary method, which is the primary method of a GI bounce and then a secondary method. And by default, we only have this primary method. a because in reality, light bounces way more than just one time, that's where this secondary method comes in. So the primary method controls the very first bounce of light, and then the secondary method controls any bounces beyond that first one, okay? So what I can do is go in here and choose a bunch of different types here, and there's always a couple different types for this primary method as well. What you need to know about all these methods is that this QMC or quasi Monte Carlo is the most accurate type of of GI calculation, but it's also the most render intensive. Okay. And the QMC is mostly used for more outdoor scenes. And this irradiance cache or IC is more useful if you have like an indoor scene or if you're using area lights. So for our scene, we're using a bunch of area lights and it's technically like a studio setup, so that's indoor. So I'll just leave that at irradiance cache. Now the secondary methods, we actually have a lot more options as far as secondary methods go. So we have our QMC and our IC again. So good for outdoors, good for indoors with area lights radiosity map is a less accurate but faster rendering rendering type of calculation that is More suitable for outdoor kind of scenes Okay, so if you're if you're not using a bunch of area lights or anything like that and then light mapping is a faster version of the irradiance cache which is very useful for indoor scenes and again using area lights as your light source. You can see how much brighter our scene is because we're adding more light bounces and because more light is diffusing through our scene it's brightening up all the little nooks and crannies of our scene right now. So just like we use this ambient light to kind of brighten up and fill in all of the nooks and crannies of our objects of our scene right now, global illumination basically does the same thing, but way more accurately. Okay. So in our presets menu here, we actually have a ton of preset lighting setups or global illumination setups that are very good starting points for different circumstances. are settings as well. And then there's all these other ones which I'm not going to get into if you want to dig into the deep end of GI. Definitely use that show help to figure out where all these do. But just for preview purposes, let's go and just choose this interior preview, high diffuse depth. Now I'm going to let this go and let's just talk about what does high diffuse depth mean and what is this maximum depth that shows up here. So remember I was saying that this primary method is that first bounce of light. So the light gets cast, it hits an object, and then it bounces once, and the primary method controls that first bounce, okay? The secondary method is bounces beyond that first bounce. And you can actually control how many bounces by using this maximum depth. So right now we have the first bounce and then 16 more bounces of light. So the more bounces you have of light, the more calculations and a slight increase of render time occurs as well. So what a high diffuse depth means is that the depth of how diffused and bounced out your light is, is controlled by this maximum depth how light is going to bounce that much less. So it's going to have the initial bounce and then bounce four more times. And you're going to see that this actually doesn't change that initial first bounce, but our scene is much less blown out and it's a little less bright because there's less light diffusion happening. Okay. So before I go any further, let me just turn off this ambient light altogether because what that ambient light is actually doing is reenacting that G. and that are seen is still pretty bright. So when you turn on GI, you might need to adjust the strength or the intensity of some of the lights in your scene. Something else you can do to adjust your light values or your luminant values of your scene is to adjust this gamma. Okay, so this basically brightens up the luminance of your image altogether. So if I make this, if I change the gamma to two, what you're going to notice is that's going to brighten the scene up overall. And a lot more of our scene is a little bit blown out. But if I go ahead and change this gamma to maybe 0.5, you're going to see that this actually doesn't affect the first bounce that's coming from our primary method. It's actually, it's actually affecting the secondary bounces. So you're seeing that the scene and the, and the bouncing lights of our scene. So a lot of the parts and the bouncing lights of our scene so a lot of the parts of the walls and stuff like that which are accepting those secondary bounces are much darker. Okay, and I can bring this to like point one and really see what's going on here and really what we're doing is just really darkening those secondary bounces and now you're seeing it looks like we just have a single bounce and not a lot of the nooks and crannies or darker areas of our scene are getting very bright bounces there. So let me just bring that up to one again. So that's kind of the primary method and the secondary method and you can control those as much as you want some render faster than others here. But what another thing GI allows you to do is use objects that have luminance materials on them to act as light sources. So what does that mean? So let's just go ahead and turn off all of our lights. I'll deactivate all of our lights by changing their checkboxes to X's, X amount. And what I'm gonna do, and you're gonna see that nothing is rendering in my scene. My scene is dark because there's no light emitting, right? So what I'm gonna do is let's create one of those little soft box planes here. So I'm just gonna create a plane that's gonna act as a soft box and let's go ahead and let's change this planes orientation to positive Z. So it's gonna be facing our subject here. And let me just kind of move this, let me scale this down. Let me just angle this slightly, okay? So I'm just angling it up as if this was going to be like a key light. So it's angled. It's a little bit 45 degrees to the right of my scene. It's hanging out right there in the corner. And let me double click in my Material Manager and rename this Luminance. And what I'm going to do is turn off the color and the reflectance. Remember how we applied Lumin materials and activated the luminance channel on our little softbox plane objects there? So I'm going to do the same thing. And what I'm going to do is then apply this luminant material to our plane. Okay. So what happens is any object that has a material that has luminance activated, GI with GI turned on, treats that luminant object, that luminant material object as a light source. So it gets light information from those luminance objects. So you can see that we're getting this plane object with the luminance is actually emitting light and casting shadows. Now what I can do is go in here and crank this up to 300% brightness. And you're going to see this is actually brightening how bright that plane object is. And it's going to scatter more light throughout the scene. It's going to have a little bit more intensity. OK. So this is kind of like an area shape in a way. But we just have a plane with a luminant material on it. OK. So what I can do is command click and drag duplicate this plane and maybe move this over to the side to act as like a fill light. And now we're gonna have two plane objects with luminance materials and these two plane objects are lighting our scene, which is pretty crazy, right? So GI allows anything that has luminance materials on it, and our luminance values activated in the luminance channel to act as a light source. And what you're seeing is some splotchy lights and shadows happening in our render here. And that's mitigated by samples in the GI settings. So you're gonna see we have the sample settings here. If I turn this down, the accuracy is set pretty low. But we can go ahead and maybe change the samples to medium, which is gonna jack that up to an accuracy of 75%. And just like upping samples on an area shadow, an area light shadow, it's going to help smooth out and get rid of that splotchiness and get rid of that grain. So this is something you might need to play around with depending on your scene and your light sources. Okay. So one thing we can do is even change the color of a material in our scene. So right now we just have just this clay material. So let me go and just create a clay material. Let me go and create a new material. Let's make this blue. I'm just going to add that to the color channel. I added that to the luminance channel. I didn't mean to do that. Let's just grab this teal color. Let's apply this to our background Psyche. I'll just replace that material so now our floor is blue our psych is blue watch what's actually gonna happen in our render so it's rendering we got our blue background you're actually seeing the blue floor the blue psych being bounced that color is being bounced onto our objects so that's something very similar that happens in real life where if you're in a red room which would be pretty crazy but if you're in a red room you're gonna see that red bounced light that's bouncing off that red floor or that red wall and kind of it's it's spilling onto the objects in your scene so that's what's happening with GI on with this blue floor this blue psych as well so it's it's this combination of objects in your scene, those colors kind of bouncing and making for a way more realistic scene here. So another thing you can do aside from just having plane objects or any objects with luminant materials on it is if you remember, let me just delete these planes, if you remember and you watched the HDRI bonus video, you know that we can grab a sky object and throw an HDRI image on there. So watch what actually happens when I put a sky in here. A sky is basically just a giant sphere with no material on it. And since it's got no material on it, it's going to default to that gray. So that gray color is actually acting as a gray luminance, giant, luminant light that's lightening up our scene. So what I can actually do is go into my content browser and I showed you how you can navigate to the HDRIs in your presets. You can easily just go to that and click on this little magnifying glass and just search for HDRIs here as well and I'll just hit enter. And you're gonna see all the HDRIs that you have preloaded in your content browser show up here. Okay. So let me just grab. Let's go and just go into this folder right here with the HDRs and let's grab this clear sky buildings HDRI and let me just drag and drop this into my material manager and you're going to notice it's kind of like a blue tint to it. So let me just close that out and I'm going to just double click and show you that there's a reason why when you bring in an HDR preset image, why that image is loaded in the luminance. So you can use this image as a light source. So let me just apply this to my sky and watch what happens. Immediately things are scenes going to be much, much brighter. Now what's actually going on is let me just go and apply that clay material back onto my psych so we're not kind of confusing where that blue light source is coming from. So now it's just got that basic gray material on our psych yet our scene still has that blueish tinge. And that's all from the fact that our HDR image is being used to light our scene. So it's going to be based on the luminance values. So all the bright parts of our scene are going to be translated to very bright, luminance light sources. And the darker areas are going to be darker sources of light. So again, if I go into my image options here by just clicking this path, this file path, I can go in the exposure and darken this image down. And what that's gonna do is because all of our illuminant information from our global illumination is being derived from the brightness or the bright areas of this image, if we darken the exposure, it's actually gonna darken our scene because the the the luminant values are gonna be much darker The the color values are gonna be much darker as well So if I crank this really high if I bring this to an exposure of like two You're gonna see that our scene is much brighter and what this is gonna mean is that our our HDR image our sky is gonna be a giant bright Luminance source of GI bounced light and this is just way too much and the and pointing down towards this box with a plus sign. What that's gonna do is just write over that HDR. If I close out, you're gonna see that because we changed our HDR image and because it's a much brighter image and there's a lot more bright luminance values in that image, it's now blowing out and totally changing the look of our scene from the GI light that's being bounced. So for such a light source like this that has a lot of really bright values in here, maybe we want to bring down the exposure so it's not so blown out and you're just kind of darkening down all the lighter values now. So it's not so blown out, but you're going to see that that yellow and green that's cast from the luminant green values from the trees and then the very bright Luminate values of the Sun and the sky is going to be bounced in You're going to see all those hues show up in our render. Okay, so let's just try one more this Let's try this basic photo studio, which is like a virtual photo studio and we got all these little Umbrella tents Light umbrellas in here and again, let's just write over this other material here. And let's see how this changes our scene. And because this is just a bunch of gray values and there's no colors in the scene aside from the little red dot right there, that's why you're not seeing any kind of hues being introduced into our scene because there's no hues in our image that is being acted that is being treated as a luminant light source. And so all you're seeing are all these kind of gray values. And again, I can go in here and change the exposure and maybe brighten that up. And we're gonna have a much brighter light, much more bright luminance values that are gonna be hitting our objects. So the one thing I wanna say about GI is that it's not 100% necessary to have for a render, okay? So it's only necessary if you're really going for super realistic renders because the fact of the matter is, is I could go ahead and just delete my GI, right? And just turn on my lights, delete my sky, and if I position my lights correctly and utilize my lights correctly, I can actually recreate or reenact those bounces of lights by strategically putting a light where a light bounce would hit. So that's kind of the point of this rim light or these background fill lights is to kind of emulate the light that would hit the background psych and then bounce off and hit the backside of our objects here., like I said, it's not super necessary if you decide in your 3D career that man, you want to really get into some really hyper realistic renders. GI is really gonna be the way to go. And on top of that, third party renders like Octane, Redshift, and stuff like that actually calculate GI in the ambient occlusion much much much faster than the just native renderers inside of Cinema 4D can. So definitely like GI is a huge huge deep subject and again if you want to know more about it definitely go into the global illumination check out all the settings remember that right click show help is gonna be your best friend and you can really dig deep into what all of these different GI settings are and really Start understanding how you can use it in your own workflow So definitely check that out and again if you really think you want to go in the realistic render route Definitely research some third party renders as well But that's GI in a nutshell. Again, it's a huge subject. Learn at your own risk and use that show help. Alright? Happy rendering.",
+  "language": "en",
+  "confidence": null,
+  "duration": 1416.58
+}