Podcast
Questions and Answers
Which light source type is primarily used as a simplified method to approximate the effects of inter-reflections within a scene?
Which light source type is primarily used as a simplified method to approximate the effects of inter-reflections within a scene?
- Area source
- Distant point source
- Global illumination
- Ambient light (correct)
Which of the following is NOT considered a primary factor in determining the brightness of a pixel in an image?
Which of the following is NOT considered a primary factor in determining the brightness of a pixel in an image?
- Surface orientation
- Light source strength and color
- Surface material and albedo
- Sensor temperature (correct)
What is the term for the fraction of light that a surface reflects?
What is the term for the fraction of light that a surface reflects?
- Albedo (correct)
- Specular exponent
- Diffuse coefficient
- Reflectance
What information can differences in intensity within an image provide about the depicted scene?
What information can differences in intensity within an image provide about the depicted scene?
Which of the following best describes 'color constancy'?
Which of the following best describes 'color constancy'?
In computer vision, what is a primary limitation in achieving color constancy compared to human vision?
In computer vision, what is a primary limitation in achieving color constancy compared to human vision?
In the context of color correction, what is the fundamental assumption behind the 'White World Assumption'?
In the context of color correction, what is the fundamental assumption behind the 'White World Assumption'?
What's the main idea behind applying the 'Gray World Assumption' for color correction?
What's the main idea behind applying the 'Gray World Assumption' for color correction?
Which color correction technique involves selecting a known color within an image to serve as a 'white' or 'gray' reference point?
Which color correction technique involves selecting a known color within an image to serve as a 'white' or 'gray' reference point?
What is the primary difference between a local illumination model and a global illumination model?
What is the primary difference between a local illumination model and a global illumination model?
Which type of light source is characterized by having a single, well-defined illumination direction, such as sunlight?
Which type of light source is characterized by having a single, well-defined illumination direction, such as sunlight?
Which of the following exemplifies an area light source?
Which of the following exemplifies an area light source?
If an image appears too red, which color correction method would adjust the green and blue channels relative to the red channel?
If an image appears too red, which color correction method would adjust the green and blue channels relative to the red channel?
How does proximity of a surface influence intensity in an image?
How does proximity of a surface influence intensity in an image?
What is the main purpose of color correction techniques?
What is the main purpose of color correction techniques?
Which step is performed in the Gray World Assumption method?
Which step is performed in the Gray World Assumption method?
Which best describes the type of light that accounts for inter-reflections in a modeled scene?
Which best describes the type of light that accounts for inter-reflections in a modeled scene?
If you have a picture that appears to have too much blue light, which color correction method would you use?
If you have a picture that appears to have too much blue light, which color correction method would you use?
What is the function of albedo?
What is the function of albedo?
You have a system that only estimates the light and surface of objects. What kind of illuminator are you using?
You have a system that only estimates the light and surface of objects. What kind of illuminator are you using?
Flashcards
Inter-reflection
Inter-reflection
Light that bounces off surrounding surfaces, significantly contributing to illumination.
Distant Point Source
Distant Point Source
An idealized light source infinitely far away, providing parallel light rays.
Area Source
Area Source
Light source with a physical extent, such as walls or lamps, emitting light from a surface.
Ambient Light
Ambient Light
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Global Illumination Model
Global Illumination Model
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Pixel Brightness Factors
Pixel Brightness Factors
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Intensity and Shape
Intensity and Shape
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Color Constancy
Color Constancy
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Color Correction
Color Correction
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White World Assumption
White World Assumption
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Gray World Assumption
Gray World Assumption
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White Balancing
White Balancing
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Study Notes
- Local illumination models consider light, surface, and camera properties.
- Inter-reflection from surrounding surfaces is a significant light source.
Light Source Models
- Distant point sources provide one illumination direction, for example, the sun.
- Area sources include white walls, diffuser lamps, and the sky.
- Ambient light is used as a substitute for complex inter-reflection calculations.
- Global illumination models account for inter-reflections within a scene.
Pixel Brightness
- A pixel's brightness hinges on several factors: light source characteristics (strength, direction, color), surface orientation, surface material and albedo, reflected light and shadows, and sensor gain.
- Pixel brightness alone reveals little information.
Intensity Variations Indicate Shape
- Intensity variations are caused by changes in surface normal.
- Intensity variations are also caused by texture.
- Intensity variations are also caused by proximity.
- Intensity variations are also caused by indents and bumps.
- Finally, intensity variations are also caused by grooves and creases.
Color Constancy
- Color constancy involves interpreting surfaces based on albedo or true color, rather than observed intensity.
- Humans excel at color constancy.
- Computers are not nearly as good at color constancy.
Color Correction
- Pixel colors can be adjusted using constants.
- White World Assumption: normalizing color channels by the largest value, assumes the brightest pixel is white.
- Gray World Assumption: adjusting color channels assumes the average color should be gray.
- White Balancing: correcting the image by choosing a reference point as the "white" or "gray" color.
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