Lighting a 3D Scene

1. Lighting a 3D Scene Guilford County Sci Vis V204.01 part 1

2. A. Lights and Shadows in a 3D scene. • 1. Most 3D programs have some type of _____DEFAULT______ lighting that can be changed to create a more realistic appearance of objects in a scene. The standard or default lighting does not represent real world lighting, but it is simple and fast. Numerous controls exist to modify the default settings and produce realistic images.

3. 2. CG (Computer Graphis) lighting typically includes four elements. • Where in the scene the light is located (usually specified by X, Y, Z coordinates from the keyboard or by mouse operations) • Intensity of the light or how bright it is (usually specified with a range where the higher the number, the brighter the light) • Color (commonly specified using RGB values, i.e. black=0,0,0, white=255,255,255, pure red=255,0,0) RGB of 0, 0, 0 = black; 255, 255, 255 = white; 255, 0, 0 = pure red, etc. • Angle of incidence specifies that the more a surface is angled away from a light, the darker it appears. When the angle is 90˚ to the surface, the surface is lighter.

4. The Type of Lights • Point • Spot • Ambient • Directional

5. 3. There are several basic types of CG (computer graphics) lights. • Point lights, also known as omni lights or local lights, simulate a single light bulb. They radiate light equally in all directions.

6. Point Lights • Shines light in all directions (much like the sun). • Good for acting as a light from a light bulb or a candle.

7. Point Lights • Also known as omni or local lights. • Have location but no direction.

8. Spot Lights Spotlights throw light rays in a certain direction radiating from a single point in space. • 1. Spotlights produce a circular pattern of light known as the hotspotthat grows elliptical in shape as the angle of the light’s centerline decreases. • 2. The intensity of the light fades with an increase in its distance from the centerline of the cone to its edge. This fading is known as dropoff. • 3. The width or spread of the cone can be controlled in most programs

9. Spot Lights • Spotlights produce a circular pattern of light known as the hotspotthat grows elliptical in shape as the angle of the light’s centerline decreases. Falloff Hotspot

10. Spot Lights • Behaves just like a real-world spotlight. • Good for imitating beams of headlights and focused lamps (lamps with shades).

11. Spot Lights • The intensity of the light fades with an increase in its distance from the centerline of the cone to its edge. This fading is known as dropoff. • The width or spread of the cone can be controlled in most programs

12. Ambient light Ambient light simulates the overall amount of light in the world around you. • 1. Ambient light does not come from any one point, nor does it extend in any one direction. • 2. Ambient light does not cast shadows; it lights all objects evenly and uniformly throughout the scene.

13. Ambient Lights • Can shine light everywhere uniformly. • Good for filling the scene with overall light. • Does not cast shadows.

14. Directional or Infinite Lights Infinite or directional light simulates the great distance of the sun by producing light rays that are parallel to each other, but that shine only in one direction. • 1. All objects in the scene receive the same amount of light. • 2. It is easy to get a decent rendering with only a single infinite light.

15. Directional or Infinite Lights • Shines light in the direction of the arrow. Placement not important. Acts like ray fram a laser. • Good for directional fill lights in an outdoor scene. • Not very effective with indoor lighting with shadows turned on.

16. Directional Lights

17. Light Icons • Lights do not have size or shape. Although represented by icons, lights do not appear in the rendered scene, only their effects

18. 4. Colored Light • a. Colored lights can be used to create special effects. • b. Colored lights typically are not used as general lighting within a scene, but can be used to emphasize time. For example, use a yellow cast in a late afternoon scene, a pinkish tint to represent mornings, and white to represent noon. Longer shadows occur in the afternoon. Morning light is softer. Mid-afternoon light is hard and sharp. • c. Colored lights can be used to emphasize mood. For examples, red, orange, and yellow imply passion or anger, green implies peacefulness, and blue implies sadness or depression.

19. 4. Colored Light • d. Color is a visual indicator of temperature. For example, use red to represent warmth and blues to represent coolness. • e. Objects in the real world derive their color, in part, from the reflections of objects around them. In computer graphics, color is pure. Blue light shining on a yellow object will cause the object to turn green. • Before starting your lighting, write down how you want the scene to look when it is finished. • g. The more lights you use, the longer the render times and the more RAM you will need.

20. 5. The classic lighting layout The classic lighting layout (suggested as a starting point for lighting) consists of three lights. • a. Remove all default lighting from the scene, the scene is now black. • b. Key light – the primary light source in the scene. It is usually placed off to the side of the main feature in the scene. It is the strongest, brightest light. Typically it is the only light in the scene set to cast shadows. Local lights and spotlights are often used as key lights.

21. 5. The classic lighting layout (cont.) • c. Fill light – the real world contains a certain amount of ambient light that is always present. In the computer scene the only light that appears is that which is inserted. The fill light is usually 25% – 50% the strength of the key light and is used to add enough light to soften the light provided by the key and to reduce or eliminate unwanted shadows. Place the fill light opposite the key. • d. Backlight– adds depth to the scene by separating the objects from the background, giving them more of a defined shape. As the name implies the light is placed behind the objects in the scene and is about 50% – 100% the intensity of the key.

22. Classic lighting • Classic lighting in 3D needs three types of lights. • Key Light • Fill Light • Back Light

23. Setting Lights in 3D Scenes • Start in Darkness. • Add a Key Light. • Creates the subject's main illumination, and defines the most visible lighting and shadows. • Represents the dominant light source, such as the sun, a window, or ceiling light - does not have to be positioned exactly at this source.

24. Adding the Key Light • Create a spot as the Key. • In the top view, offset the Key Light 15 - 45 degrees to the side • From a side view, raise the Key Light above the camera, so that it hits your subject from about 15 - 45 degrees

25. Adding the Key Light

26. Adding the Key Light • The key light is brighter than any other light and is the main shadow-caster. Specular highlights are triggered by the Key Light. • Do a test-renders. The scene should have a balance and contrast between light and dark, and shading that uses all of the grays. • The "one light" looks almost like the final rendering, except that the shadows are pitch black and it has a very harsh contrast .

27. Key Light Only in a Scene

28. Adding the Key Light • The Key light is generally placed at a 45 degree angle from the subject.The angle of the Key light is determined by what kind of mood the scene needs.

29. Adding the Key Light • Top view: The Key light is placed next to the camera. Generally, place the Key Light at an approximately 35-45 degree angle to the subject

30. Add The Fill Light • The Fill Light softens and extends the illumination provided by the key light, and makes more of the subject visible. • Fill Light can simulate light from the sky (other than the sun), secondary light sources such as table lamps, or reflected and bounced light in your scene. • With several functions for Fill Lights, several of them can be added to a scene. • Spot lights are the most useful, but point lights may be used.

31. Add The Fill Light • From the top view, a Fill Light should come from a generally opposite angle than the Key - if the Key is on the left, the Fill should be on the right - but don't make all of the lighting 100% symmetrical! • The Fill can be raised to the subject's height, but should be lower than the Key.

32. Add The Fill Light

33. Add The Fill Light • At most, Fill Lights can be about half as bright as the Key (a Key-to-Fill ratio of 2:1). For shadowy environments, use only 1/8th the Key's brightness (a Key-to-Fill ratio of 8:1). • If multiple Fills overlap, their sum still shouldn't compete with the Key.

34. Add The Fill Light • Shadows from a Fill Light are optional, and often skipped. To simulate reflected light, tint the Fill color to match colors from the environment. Fill Lights are sometimes set to be Diffuse-only (set not to cast specular highlights.)

35. Add The Fill Light

36. Add The Fill Light • Front View: The Fill Light is generally placed slightly lower then the Key Light. Here it is on almost the same elevation as the Key Light

37. Add The Fill Light • Top View: Place the Fill Light at a 90 degree angle from the Key Light

38. Add Back Light • The Back Light (also called Rim Light) creates a "defining edge" to help visually separate the subject from the background. • From the top view, add a spot light, and position it behind the subject, opposite from the camera.  From the right view, position the Back Light above the subject

39. Add Back Light.

40. Add Back Light. • Adjust the Back Light until it gives a nice "rim" of light, that highlights the top or side edge for the subject.  (Some people call a light that highlights the side edge a rim light.)  • Back Lights can be as bright as necessary to achieve the glints needed around the hair or sides of the subject. Unless one can avoid the need for shadows with careful aiming, a bright Back Light often needs to cast shadows.

41. Add Back Light. • A Back Light is not a background light - it creates a rim of light around the top or side of the subject No Back Light (left), Back Light added (right).

42. Add Back Light • Side View: The Back Light is pointed at a sharp angle towards the subject. Be careful here, If the light is placed too low or if the angle is set too close to 90 degrees the light will spill over onto the face or frontal areas of the subject.

43. Add Back Light • Top View: The Back Light is placed directly opposite the camera and behind the subject

44. Add Back Light

45. The Lighting Setup

46. Using Light to Convey Time • The color and angle of a light place a scene in time and space. For morning or evening scenes, make the sun a warm color such as yellow, orange, or red. Then place the light source at a low angle

47. 6. Lighting moods • a. High key lighting places the key light in front of and above the items in the scene to create interior, daylight scene. A 50% intensity fill light is placed in front of the items and off to the side. Place the back light at ground level at 1.5 times the key. • b. Low key lighting is a key light placed higher in the scene than in the High Key setup. The key is often placed to the side. Low key settings are used for nighttime scenes.

48. 6. Lighting moods(cont.) • c. Frontal lighting does what the name implies; it places the key in front of the scene, but it also places the key high above the scene to produce an effect similar to an overhead light would produce. • d. Side lighting places the key light at eye level and in front of the scene to produce light that simulates sunlight.

49. Morning or Evening Light

50. Using Light for Noon • Cooler white lights placed at a high angle suggest the sun shining at midday. To make a midday scene more interesting, add clouds to the sky and project shadows from them • Fill lights above the ground should be blue or gray to match the sky. Fill lights below the ground should be green or brown to match the earth