Image-based lighting

Transcription

This tutorial is about Image Based Lighting in Maya. I've got a scene open here in Maya, just a room with no ceiling. Step one is opening my Render Settings. So I click this button here, Render Settings will open up, and I need to make sure that Mental Ray is turned on. Image-Based Lighting is a feature of Mental Ray, it won't work without Mental Ray. To find image-based lighting we go to the Indirect Lighting tab, and image-based lighting is the first option. I'll hit 'Create' to create a new IBL node, and a couple things happen. First we get this yellow sphere in the background, and the image-based lighting node opens up in our Attribute Editor on the side here. Then we just plug our texture in by clicking on the folder next Image Name, and we point it at whatever image we want to use for lighting. And we will see that this yellow sphere is something that I can manipulate in the world. So, in this case, I'm rotating it so that I can have the sunlight come in through my windows. Now for a point of reference, here's my original render. now we're going to compare it to the image-based lighting we just turned on. When my new render does pop up, I can see that it looks different, it looks a bit brighter, but it still doesn't look quite correct. So what's going on here? We need to go back into our Render Settings and under the 'Common' tab, that first tab on the left, we need to scroll all the way to the bottom and find our Render Options. We need to turn off 'Enable Default Light'. Otherwise Maya is going to render that on top of our image-based lighting. When I do re-render my scene, I see that my scene is very very dark. We're not actually getting a lot of image-based lighting. All the lighting we saw before was from the Default Light. We want to fix that. We'll see that there is an 'Emit Light' button on our IBL node. We need to turn that on so that it actually creates light. Duh, right? When I re-render, we'll see the lighting is very different. We actually get lighting now instead of just having a black environment. But we could use a little bit more light. One thing that we can do is go to the Render Settings. go to the Indirect Lighting tab, and turn on 'Final Gathering'. That will add a little bit of light, but we still need a little bit more. So we're going to create a new light, a 'key' light, and that's going to be a Directional Light. So: Create > Lights > Directional. That Directional Light is going to act as my sun, as my main light source. In this fashion we can add a lot of light to the scene very quickly. I'll scale the Directional Light up in the viewport, just to make it easier to work with. And then I'll rotate it around, so that it is pointing in the same direction that the sun's rays would be. I'll re-color the light so that it is slightly orange, so it matches the sun; I can sample pixels from the image to get a good match. Then I want to make sure that Shadow Casting is on. This key light is a quick and easy way to add primary shadows to my scene. When I re-render, no big surprises, we do get more light in the scene. But let's step it up. I'm going to turn this ceiling on in my scene. That will close off a lot of the light that's coming in from the sky. When we re-render we see our scene is very different; almost entirely black. What happened here? It's very very different. Well, from a ray-tracing perspective, all the rays that are being cast from the image based lighting sphere are having a hard time getting into those windows. We've closed off a lot of areas that those rays can travel through. So what can we do to fix this? We could try playing around with our Render Settings, but the answer is not in there. We need to get more light in through the windows. I'll create a new light, an 'Area Light'. So: Create > Lights > Area Light. Then I'm going to rotate it and move it and rescale it, so that Area Light basically covers up all the windows on the side of the room. And now I have to go into the attributes that light and look for the Mental Ray tab. Under the Mental Ray tab there's an Area Light tab. I need to turn on 'Use Light Shape', so that it uses the light's shape. I'll also make it visible. Then I need to scroll down, this is the important part. All the way at the bottom, there is a Light Shader slot. I want to click to add something there, and in the window that pops up, I'm looking for Mental Ray Lights on the left side bar. I want to add a 'MIA Portal Lights'. So how does the Portal Light solve our problem? Well it's specifically designed for the situation we're in: it takes the Area Light, it basically looks behind it, and says "what's going on in the environment?" And then the Area Light projects that in front of itself. In this case, it's exactly what we need. We've got a room that's too dark because we can't shoot enough rays from our ray-tracing in there. So Portal Light should solve that, but we'll see that when we re-render it, it doesn't. That's because, in this case, the default parameters don't work. I will increase the Multiplier on my Portal Light, and after that adjustment, when I re-render, I get something that looks more correct. We've got a lot more light in the room. There are some things we have to tweak: for example, the ceiling is a little bit too bright. The far side of the room is a little bit too dark. Both are easy fixes. First, I tilt my area light down a little bit. We'll see that that darkens the ceiling. For the far side, I'll add a new Area Light, I'll position it so that it fills the windows. in the attributes, I'll make sure that I'm Using Light Shape, I'll attach a Portal Light node. Now we see the far side of the room is just a little bit brighter. It feels a little bit more correct, for the lighting setup that we have. In the previous renders, we do get a lot of grain. To resolve that that I went to the Quality Tab in the Render Settings window, and just dragged the Quality Slider up to create this render. As a final touch, I add light fog using a Parti Volume, and that's it! I'm James Taylor, subscribe to my channel or go to METHODJ.COM for more. Thanks for watching! 0:19:52.958,1193:02:47.295