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Author: Martin   Level : Intermediate   Environment : Maya 7.0
User Rating  : * * * * *  
 
 
We have to experiment a lot to get a good result. Most often, however, my best outputs are from a proper workflow. This tutorial discusses the workflow, focusing on maintaining control of your lighting.

Getting Started.

a. Monitor Calibration.

If your monitor is not adjusted properly, then your output will vary from monitor to monitor. If you send your output image to someone else, either it will be burnt or dark. No two monitors show an image exactly the same way, you can at least see that you meet a basic minimum requirement. The controls for adjusting a computer display vary between brands of monitors, color-matching software and video cards. To adjust the brightness and contrast, you can use the Figure 1 below. We should be able to see the first and last digits in the image.
Monitor calibration
Figure 1. Monitor Calibration.

b. Start in Darkness.

So you did your monitor calibration. Now start a scene in total darkness. Put your key light first and then all others. This will give you an overall control over the scene. In live film this is not practical because of natural light. Luckily for us, we don't face that problem in the computer graphics world.

c. Ambient Light.

In the real world, ambient light is widely distributed, "indirect" light that has bounced off objects in the environment. Dark or shadowed areas of a real room are sometimes made visible only by the ambient light. In the real world ambient light is tinted as it bounces around the environment and adds different colors to different sides of objects, based on colors it has picked up from the environment. This is a light source with no particular source location or direction. Ambient light appears to come from everywhere at the same time, like sunlight on a hazy day. Ambient light is typically used to control the overall brightness and color of a scene. An ambient light shines in two ways-some of the light shines evenly in all directions from the location of the light (similar to a point light), and some of the light shines evenly in all directions from all directions (as if emitted from the inner surface of an infinitely large sphere).
Ambient Light
Figure 2. Ambient Light

d. Point Lights.

Point light emits light uniformly in all directions, like a bare light bulb or glowing star in space. In the real world, there is no light that is uniformly Omni directional. Most sources emit light in some directions than others.
Point Lights
Figure 3. Point Lights.

e. Spot Lights.

Spotlight is a convenient light for many artists because it can be controlled properly to aim light at a specific target, as shown in Spotlight (1) below.

To create a spotlight
  • Select Create > Lights > Spot Light.
    The spotlight's icon will be at the center of the grid. This is a cone shaped light with an arrow pointing out of it. It shows that the light emits a beam of light that gradually widens with distance.
  • Select Modify > Transformation Tools > Show Manipulator Tool.
    We will get two manipulators that we can move to position and aim the light precisely. The look-at point specifies where the light focuses. The eye point defines the position of the light source.
An alternative way to position a spotlight is to select the light and then select Panels > Look Through Selected. You can then dolly and pan the view to focus on the desired surface. The area of focus is where the light strikes the surface. To return to the perspective view select Panels > Perspective > persp.
SpotLight
Figure 4. Spotlight
Spotlight (1)
Figure 4.1. Spotlight (1).
Spotlight (Penumbra)
Figure 4.2. Spotlight (Penumbra)
Spotlight (Dropoff)
Figure 4.3. Spotlight (Dropoff)


Spotlight limits the light within a specified cone or beam.

f. Directional Lights.

A directional light sets a single vector for all its illumination and it's every object from the same angle, no matter where the object is located, behind or in front. All the shadows cast by a directional light are cast in the same direction and are orthogonal projections of each object's shape. The only thing that matters in placing a directional light is which way it is pointed.

A directional light is similar to sunlight. Its parallel rays strike all objects in the scene from a single direction as indicated by the arrow icon representing the light. The position of the light is not so much important as the direction that the arrow icon points to.

When you create a light, the scene view does not display its effect, by default. The scene view instead uses default lighting.

Select Lighting > Use All Lights (Hotkey: 7). This lights up the scene view only with lights you've created and not with default lighting. If you later want to see the scene view with default lighting again, select Lighting > Use Default Lighting (Hotkey: 6).

When you render the scene, by default, Maya uses all lights you've created. If you don't create any lights, Maya creates a temporary default directional light for you and then deletes it when the render is complete.

Procedure to edit the Directional light.

With the directional light selected, rotate the light in various directions. The shading of surfaces changes as you rotate the light. The more directly the light points at a surface, the brighter the shading. A directional light is affected by its rotation, not its position. As you'll see later, the position of other lights affects the lighting.

With the light still selected, open the Attribute Editor (under the Window menu). Drag the Intensity slider to various values to see the effects of intensity.
Higher values brighten the surfaces. For example, an Intensity of 1.6 brightens the lighting so much that the gray default shading of some surfaces are bleached to white.
Directional Light
Figure 5. Directional light

g. Area Lights.

A type of light source that emits light from a two-dimensional area. The bigger the light, the stronger the intensity. Area lights are used for high reflective objects to simulate the studio product photography look. The main purpose of area light sources is to generate more realistic lighting, resulting in soft shadows.

In Maya, area lights are two-dimensional rectangular light sources. Use area lights to simulate the rectangular reflections of windows on surfaces. An area light is initially two units long and one unit wide. Use Maya's transformation tools to resize and place area lights in the scene.

Compared to other light sources, area lights can take a longer time to render, but they can produce higher quality light and shadows. Area lights are particularly good for high-quality still images, but less advantageous for longer animations where rendering speed is crucial.

Area lights are physically based, so there is no need for a decay option. The angles formed with the area light and the point that is shaded determine the illumination. As the point moves further away from the area light, the angle decreases and so does the illumination, much like decay.

h. Volume Light.

A major advantage of using a volume light is that you have a visual representation of the extent of the light (the space within which it is bound).

You can use a volume light as a negative light (to remove or decrease illumination) or to lighten up shadows.

The falloff of light in the volume can be represented by the color ramp (gradient) attribute in Maya, which prevents the need for various decay parameters, and also provides additional control. The color gradient is also useful for volume fog.

You can achieve different effects with light direction. Outward behaves like a point light and Downward acts like a directional light. Inward reverses the light direction for shading, giving the appearance of inward illumination. When using shadows with the Inward light direction you may get unexpected results. In all cases the light shape dictates the extent of the light.

Testing Your Lights.

Managing all your tests and revisions efficiently is an important part of producing high quality renders. In a scene with several lights, we need to know what each specific light is doing for you, and which light to adjust if we don't like the shading of a surface. There are several techniques to make tests that clearly show the information you need to control our lighting.

a. Isolating a light.

By isolating a light we can easily find where all lights are aimed. To set up this, deactivate all the other lights in the scene. Be sure to turn off the default light. By doing these we can give attention to our specific problems and by that we can fix it. Rendering with single light is much faster than with all lights. The process of "debugging" this kind of lighting problem is made faster and more efficient by viewing lights in isolation.

b. False color lights.

We used to light our objects with several lights. When two or more lights are hitting a subject, all their illumination may overlap and blend together. To identify the illumination of each light, we can use different colors. Generally this technique is used in real lighting in film making.
False Color Lights
Figure 6.1. False color lights.
In the above background, I put two lights from different directions.

False color lights Red
Figure 6.2. Background with only red light from one direction

False color light green
Figure 6.3. Background with green light from other direction.

Overlapping red and green lights.
Figure 6.4. Overlapping of red and green lights.

Check the image above. There are two lights of different colors which blends together. Its easy to differentiate between two colors. If we are looking at normally colored lighting in figure 6.1, we might not able to tell where the light is spilling. With the false colors, the light is given its color, we can easily locate the light.

c. Comparison

This is a very simple technique, but it helps us a lot while doing lighting. Very minute differences or adjustments, which you might not be able to accurately perceive when viewing two renders side by side, can be noticed as a movement or shift in the image when you flip between them in the same window.
Background comparison

Look at the above image, in the red circle the arrow pointing down is for keeping the image in the window and the arrow pointing up is for removing the image from the same window. By sliding the bar (red arrow) we can see the previous render. So by sliding, we can identify the minor changes in our render.
Background comparison

Shading.

The materials, shaders, and textures are also factors that determine how a model responds to light. In production a test without textures can help us better see what shading the lighting is creating. Anyway, the final shading will make an enormous difference to the output.

Conclusion

I hope you will try all these tips and tricks in your production as well as in your personal work. I am expecting your reviews about this tutorial. good luck.

 
     
 
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