Overview of Today: Some important concepts in Graphics- Color Image & Pixel (象素)- Triangle Mesh（绘制）- Lighting & ShadingTransformation (变换) and Viewing
Overview of Today • Some important concepts in Graphics – Color – Image & Pixel (象素) – Triangle Mesh – Lighting & Shading （绘制） • Transformation (变换) and Viewing
Color Perception. What is Color?- Colors are the sensations that arise from lightenergy of different wavelengths·electromagnetic waves（电磁波）withdifferentwavelengths are corresponding to different colors: Human's eye are sensitiveVisible Light Regionofthefor electromagnetic waveElectromagneticSpectrumof wavelengths between 380to 760 nm750nm600nm500nm400nm1100nmInfraredUltraViolet
Color Perception • What is Color? – Colors are the sensations that arise from light energy of different wavelengths • electromagnetic waves (电磁波) with different wavelengths are corresponding to different colors • Human’s eye are sensitive for electromagnetic wave of wavelengths between 380 to 760 nm
Spectral Distribution of LightSpectralDistribution“Light"' is a mixture of manywavelengths, each withsome intensityr- E.g., White Light means lightinclude all wavelengths withthe same intensityWavelength spectral distribution:intensity as a function ofSampleColorwavelength over the entirespectrum
Spectral Distribution of Light • ―Light‖ is a mixture of many wavelengths, each with some intensity – E.g., White Light means light include all wavelengths with the same intensity. • spectral distribution: intensity as a function of wavelength over the entire spectrum
: So, colors can be represented as suchdistribution function: However, use spectrum distribution forcolor representation is too complicated, andthe corresponds is multiple-to-one. There exits a situation as differentspectrum distribution with the samecolor""(异谱同色)
• So, colors can be represented as such distribution function • However, use spectrum distribution for color representation is too complicated, and the corresponds is multiple-to-one. • There exits a situation as ―different spectrum distribution with the same color‖ ‖(异谱同色)
RGB Color Space We first introduce color space for colorrepresentation. RBG is commonly usedcolor space in Graphics- Color is represented as RGB triple (r,g,b)- People perform almost all operations on eachchannel separately- usually, each color value is a float value rangefrom 0 to 1, or 0-255 if we use 8 bit integers
RGB Color Space • We first introduce color space for color representation. RBG is commonly used color space in Graphics – Color is represented as RGB triple (r,g,b); – People perform almost all operations on each channel separately – usually, each color value is a float value range from 0 to 1, or 0-255 if we use 8 bit integers