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Lighting and Cameras Eric Sedgwick. Visual Arts Painting Sculpture Photography Cinema Cartoons.

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Presentation on theme: "Lighting and Cameras Eric Sedgwick. Visual Arts Painting Sculpture Photography Cinema Cartoons."— Presentation transcript:

1 Lighting and Cameras Eric Sedgwick

2 Visual Arts Painting Sculpture Photography Cinema Cartoons

3 References [digital] Lighting and Rendering Jeremy Birn, New Riders Publishing Some information available at Jeremy Engleman – some nice renderings art.net/~jeremy Chapters 7 and 8 of text

4 Lighting Real Lights sun, tungsten bulb, flourescent bulb, Interior lighting, sky, match, candle light bounces Cast shadows – no choice Constraints on placement CG lights May or may not cast shadows local illumination fast, but no bounces Free placement global illumination, e.g., radiosity more realistic, but computationally expensive

5 Additive color

6 CG lighting How is the diffuse shading computed? Ray-tracing Z-buffer

7 Types of CG lights I Ambient light - universal light, added to everything Point or omnidirectional light Light emanates in all directions Spot light Omni light with “barn doors” Umbra, penumbra Use for illuminating a specific area softness, spread, falloff, attenuation

8 Types of CG lights II Infinite or directional light Simulates sunlight light vector Doesn’t matter where you place it Area lights - light emitted from a surface, rectangle, sphere soft shadows portraits Expensive computationally

9 Lights in Max Default lights, one or two omnis (turn off when other lights are added) Omni Spot Directional Sunlight system Ambient (in rendering effects) By default, shadows are off

10 Lighting in Maya Default lights, a point light behind and above camera (turns off when other lights are added) Point lights Spot lights Directional Ambient Volume lights

11 Lighting Workflow Set up camera first start dark, no ambient light add light false color – helps to detect contribution of various sources

12 3 Point lighting 1. Key light 2. Fill light 3. Back light 4. (Background lights) Each “light” may in fact be several

13 Key light Main illumination Obvious source of light in the scene predominant (only?) shadow Brightest Typically above and at roughly a 45 degree angle in reference to camera

14 Fill light adds to overall illumination reveals detail, I.e. bump mapping Soften shadows Often does not cast shadows

15 backlight hair light Rim light separates subject from background important in black and white photography Usually less prominent effect in CG

16 3 point lighting tutorial Jeremy Birn’s at

17 Standard Lighting setup Key 15 to 45 degrees to side (left or right) of camera 15 to 45 degrees above camera Fill 15 to 60 degree to opposite side of camera 0 to 30 degrees above (often below key) Guidelines only – could use others for dramatic effect Low-angle (spooky), above (raccoon eyes), side key (casts unflattering nose shadow)

18 Key-to-Fill Ratio Key / fill -or- Key:Fill Remember to count all lights Low, usually at least 2:1 Reflected light, or multiple light sources Cloudy, hazy days. Scattered light Interiors with lots of reflective surfaces More cheerful High, e..g, 8:1 or more “Dark” scenes, e.g., night Suspense, drama

19 Low Key-to-Fill, Jeremy Englemann

20 High Key-to-Fill Ratio, Jeremy Englemann

21 Shadows spatial relationships composition contrast indicating offscreen space

22 Spatial Relationships Greg Gargett, Internet Ray Tracing CompetitionInternet Ray Tracing Competition

23 Offscreen Space, Adam Murphy

24 Shadow algorithms Raytracing Send ray to object, bounce ray to light z-buffer or depth-mapped shadow buffer I.e., render scene from perspective of light Should differentiate between Dark side of object, normal doesn’t point to light Object truly in shadow, another object blocks light Shadows are expensive, either way

25 Shadow tricks

26 Faking shadows Set up lights Add spot for shadow exclude object casting shadow make brightness negative Very cheap computationally Not so accurate, good for non-critical shadows

27 Shadows only light Get lighting the way you want create light to cast shadow make it cast shadows duplicate shadow light turn brightness negative, same magnitude turn shadows off Good shadow control, not cheap

28 Qualities of light softness intensity attenuation color

29 Softness Hard light Focused, sharp shadows, clear point of origin Soft light Soft shadows More diffuse Emitted from an area rather than from a single point Area light, or simulated area light

30 Soft light Jeremy Englemann Simulated area lighting multiple lights with soft shadows

31 Simulating an Area light Start with single light, get brightness right, use falloff Make multiple instances (e.g, say 5 at 20% brightness of original) Cast shadows using z-buffer with soft edges MAX: Turn up sample range in Shadow Map Params Maya: Turn up DMap filter size Much cheaper than an area light

32 Attenuation Brightness decreases with distance from light illumination at object = intensity / distance^2 CG attenuation None – far away lights (that aren’t far away in your scene) Linear – medium distance lights (that aren’t far away in your scene) Quadratic/Inverse square – lights where they are supposed to be

33 color temperature at 3DU.com

34 Practical lights

35 Cameras

36 Real Camera vs. CG “camera” Real Camera Lens Focus Amount of light Placement CG camera No lens Everything in focus (can blur) Fully adjustable light Flexible placement

37 Real Camera terms Focal length – distance from lens to film Angle of view Focal point Depth of Field – distance Aperture – size of lens opening f-stops

38 Some Lenses Super Wide angle 15mm, 78.5° Wide angle 30mm, 44.2° Normal – not too far from eye 50mm, 27.4° Portrait 70mm, 19.2° Telephoto 120mm, 10.5° Super long, I.e. nature photography 200mm, 6.1° Source: Lee Sullivan

39 Depth of Field Blur foreground (and maybe background) Deeper for longer focal length – often focus at infinity Closeups could look unnatural if background is clear Deep shots could look unnatural if foreground is too clear (less of an issue) Used for narrative, tells you what to look at

40 Types of Cameras Orthogonal Perspective Perspective view acts as a camera In Max, Can match camera to perspective view Select viewport Select camera View>match camera to view Most CG cameras don’t have a lens

41 Pyramid of Vision Aka “cone of vision” Eye point Image plane Near clipping plane – hither plane “depth of field” Far clipping plane – yon plane

42 Field elements Aspect ratio (proportion of height to width of the image) – establish early Title safe area Action safe area In configure area for viewport

43 Depth of field Portion of the pyramid that is in focus Binoculars Focus Applies to real cameras very strongly CG, usually has infinite depth of field, everything is in focus, not very realistic

44 Camera Translations Dolly – sideways motion Truck – forward/backward motion Boom – vertical motion Tracking shot – camera follows action

45 Camera Rotations about camera center, I.e., target moves Tilt – forward/backward, rotate in horizontal axis Roll – to side, rotate in depth axis Pan – left/right, rotate in vertical axis about target, I.e., camera moves Orbit

46 Lens Animations Zoom in – for close up out – widen field of view Rack focus Zoom that adjusts the focus from subject to another. Narrative tool. E.g., filming conversation

47 Some Lenses Super Wide angle 15mm, 78.5° Wide angle 30mm, 44.2° Normal – not too far from eye 50mm, 27.4° Portrait 70mm, 19.2° Telephoto 120mm, 10.5° Super long, I.e. nature photography 200mm, 6.1° Source: Lee Sullivan

48 Distance Close-up Strong perspective Can be disorienting Can be mysterious Medium Long Weak perspective Binoculars Can be objective

49 Camera Lenses Practical vs. stylistic use Focal length is inversely related to the angle of view Distortion due to perspective increases when focal length decreases

50 camera shots Low-angle High-angle Point of view

51 camera shots

52 Parallax Animation Close up motion appears faster than far away motion.

53 Camera and lights Caution: while camera and lighting effects can be dramatic they can also be highly distracting. Cameras Animate cameras –OR- objects not both Don’t use lights recklessly. They increase rendering time dramatically, particularly shadow casting lights.

54 Lights and Camera Citizen Kane Director: Orson Welles Goodfellas Director: Martin Scorsese

55 Lights and Camera example, anibyte anibyte

56 Cameras aperture lens effects motion blur shutter speed

57 Framing rule of thirds graphic weight


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