Rendering in Layers in Maya

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By: Bogdan Amidzic

Imagine this -- you are doing a shot for a film, for example, a cyber cityscape. And you use many lights, glows, fog, crafts … and of course, you turn on some form of GI or ambient occlusion. And when you press render it takes hours to render, but it...

Added: 16 July 2008 Views: 1521

Path : Computers

3D Graphics

Maya

Keywords: computers maya layers graphics render

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Render layers is one very powerful feature of Maya. You might ask why?

Here we show you how to use it properly.

In this tutorial we will be using a finished model. You can download it here.

Imagine this -- you are doing a shot for a film, for example, a cyber cityscape. And you use many lights, glows, fog, crafts … and of course, you turn on some form of GI or ambient occlusion. And when you press render it takes hours to render, but it looks really great. And then your director comes, looks at the render and says, "Wow that is really great!". You're happy cause you haven't slept for three days in order to finish it. But then he says "… but I don't like the color of that fog, make it a little brighter!" So you go and change it, but thing is that he has to wait hours for that new render. And you are very lucky if you have to change only that one thing. But in most cases he will ask you to change a million things. He doesn't have time for you to render frame again and again. So after some time, you will be fired!

But -- if you are smart, you will separate your scene in many layers so that when he comes and asks, "change the color of that craft there, change the color of the sky…", you will just change one slider in the compositing program, and the result will come almost instantly. Your director will love you, and you will get few hours to sleep.

So I used Maya and Shake to build this cityscape scene. It's very simple, I didn't have time to create a complex model.

As a starting point I used this.

Created one directional light (sun), that casts depth map shadows with 2k resolution.

Also I created four directional lights from different sides to create blue illusion of sky illumination.

When rendered, the image looks like this. You can notice that those four lights make the scene look flat. Later I'll use an ambient occlusion pass to make small details more visible.

I used blinn materials for some buildings.

I assigned a texture to it. You can notice how odd it looks. We need to fix the UVs.

Select all faces.

Use cylindrical projection to project texture from cylinder around the object. Use manipulators to fit the cylinder to your object.

I also added bump using the same texture, and used that same texture for specular color.

Select all faces that look to the sky. Use planar projection to project texture to them.

I also created few more materials.

For some parts I used automatic mapping. This will try to project the texture from different angles.

You might notice that the texture looks very big. In the UV texture editor, you can select all UVs and scale them. This will repeat the texture.

Now the cityscape is starting to take shape.

For small lights, I created very simple geometry and assigned surface shaders to them. I added a bit of glow to them. You can add glow also in compositing passes.

Now Rendering Layers. Select all objects except those tiny glowing objects (grouping and selection sets will be your great ally in this step), and in the channel box check render. This will display your render layers. By default, all objects are assigned to masterLayer. Click that second button (one with tiny blue ball), this will assign objects to the new layer you created. Double click to layer and change its name to Color. All new layers will be named layer1 by default. Check 'R' in the box to the left. That means that layer is rendered. The masterLayer shouldn't have this 'R'.

With same selection (all except the tiny glows), create new layer. Hold right mouse button on layer1 (that new layer) and you will see presets submenu. Choose Ambient occlusion. This will create a shader override for all objects in that layer. Name the layer occlusion.