Rendering with layers
Video: Rendering with layersAs with the previous project, all we have at this point is the robot matched to the scene. We have the motion matched, but we don't have him looking like he's actually in the scene. For that, we need to do some rendering tricks. For this particular scene we're going to render it very similar to the way we rendered it in the last chapter, but we're going to use what's called render layers and this will give us more control, once the render is done, and it'll allow us to composite this robot, back into the original plates, and have a lot more control.
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Autodesk MatchMover is the perfect camera-tracking companion for Maya, and it now comes bundled with Maya 2010 and later. Staff author George Maestri gives you an introduction to MatchMover's interface and automatic matching capabilities, and then shows how to import MatchMover scenes into Maya, solve for cameras, and do object-based tracking.
Rendering with layers
As with the previous project, all we have at this point is the robot matched to the scene. We have the motion matched, but we don't have him looking like he's actually in the scene. For that, we need to do some rendering tricks. For this particular scene we're going to render it very similar to the way we rendered it in the last chapter, but we're going to use what's called render layers and this will give us more control, once the render is done, and it'll allow us to composite this robot, back into the original plates, and have a lot more control.
Now this is the way normally do it in high end studios, because you really want to finish shots like this in a compositor. Let's go ahead and do a quick render. So, as you can see, I've got the robot. I've got the lighting set up, and I also have some shadows that cast along this ground plane and the building. I don't have any textures on either, so we need to make sure we set up the texturing for that, as well as get the robot separate from the background. So, what we're going to do is create two layers: one for the robot and one for just the shadow.
And then when we go into a compositor, then we can have a little bit more control over color and contrast and that sort of thing. So, I'm going to go ahead and close this, and let's go ahead and start working with this. So, first thing I need to do is set up the shadow layer. So, what I'm going to do here, is actually create what's called a layer. In our channel box, if I click here, you'll see we have, basically, our channel box which is all of our translate rotate and scale, but at the bottom, we have our layers menu here.
And the layer menu I want to look at right now is the render layers. We have our display layers, which allows us to turn objects on and off, but render layers allows us to create multiple passes when Maya goes to render and it actually is very simple to use. So, let me show you how this works. First thing you want to do is set up a shadow layer. I need to figure out exactly what's involved in creating that shadow. Well, of course I need something to receive the shadow. So, I need the building and the ground plane and I also need something to cast the shadow, so I need the robot and I also need the lights to get that lighting into the scene.
So basically, I need everything. So I'm just going to go edit, select all and that just selects everything in the scene. Then I'm going to go to my layers menu and just go create layer from selected and that creates a render layer. I can double click on that and just type the word shadow. So, this is going to be my shadow layer. Now, if I just render this, you'll see that it's pretty much the same as we had before, because I haven't done any changes to it.
So, what I need to do is make the robot disappear because I don't want this image in the shadow layer. I want the shadow just to be there, and whatever it's being cast upon. So, let's go ahead and work with the building and ground plane first, and those, we'll pretty much do the same way we did the last time, is, we'll select both of these, and we'll apply what's called the use background shader. So, we can go here; we can just go assign new material, use background and you can see that turns green, and I just want to make sure I turn my reflection limit down because these are not reflective.
And then let's go back over here to our channel box and make sure we have our shadow layer highlighted and do a quick render. And you can see now that by adding that use background shader, it's gone ahead and sucked up the pixels from the backing plate. So now, we've got that part done, but we still need to make the robot disappear. We could do that very simply by selecting the robot. So, I'm going to go into my Outliner and here I have a note called Robot Master. So, I'm going to go ahead and select that, and I'm going to apply a new material to him.
I'm actually just going to apply a lambert material. It can really be any type of material, but lamberts are simple because they're not reflective and then I'm just going to turn the transparency all the way up. What I'm doing here is I'm actually using a little trick of the way that the Maya renderer works. In the Maya renderer depth map shadows don't work with transparency, which means a transparent object will still pass a shadow and we can use this to our better effect here. So let's go ahead and just render that and you can see now the robot's disappeared but he's still casting a shadow which is great.
So now, I have just the shadow. So now, I'm going to go back to my master layer and let's go ahead and render that and see what we have and my master layer is basically what I had before. And the reason I did this was to show you that I've actually got two different types of layers, and just by activating that layer, and changing the render parameters, Maya will remember those, and then, when you go to render, it will just go ahead and apply those to that layer and render out every layer that you have.
So what I'm going to do here is go back to my Master layer, go into my Outliner, select my robot, plus there are two spotlights in the scene. So I'm going to select the robot, and the lights that are illuminating the robot and then all I'm going to do here is just do create another layer from selected. So now, I have another layer, and notice how when I click on this, there's nothing but the robot. So I'm just going to double click on that, change it to robot and now I've got my master layer which is everything and that's not going to render.
I can actually turn it on and off here but what I want to render is the shadow layer which does this and the robot layer, which does this. It's just the robot. Now the one thing I still have is I still have this image plane behind the robot and I need to delete that before I actually go to render, because I really want to render this against black so that way I have a very clean plate when I go to composite it. So, I need to get rid of my image plane. So, what I need to do here is just select my camera and the way that I do this, there's a number of ways of doing it, but I just go into my Hypergraph.
Once I have my camera selected and typically attached to the camera is the image plane and all you have to do is highlight that and delete it and once I do that, when I go to render, now I have the robot against black. Once I have this set up, I can go ahead and do my render and what will happen is when it goes to render, it will create directories within your project file called robot and shadow and it will actually fill those with the renders. So, if I go into view image and I go into my project here, you'd see under images I'd have a couple of directories here.
I have one for the robot and one for the shadow. So, these were created when I rendered. So, when I select this I have, just my robot against the black background, which I can use in compositing. So, those are some of the tips for using render layers to get more sophisticated renders, so that you can composite. So now, once we're done with this, let's go ahead and go into Backburner, which is going to be our network rendering where we can do a lot of this rendering and then we'll move on to Toxic and composite it all back together.
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