Maya Optics

DI He

Introduction

The term of optics can be largely related to many scientific fields, related the physical concept in Maya software are not very different, therefore lighting and shading processing in Maya is often hard and confusing. Especially for the users who assume that the fundamental concept of optics in Maya are the same as the one in physical world, it is important that CG artists understand the difference between physical optics and Maya optics.

Chapter 1 Color.

Human eyes are lying on personal visual sensitivities of eyes, there are no red or green colors in physical world but different wave length of electromagnetic. Color model is the simplified way that colors can be represented in computer graphic application. Most of color model representation are based on human vision experience of visible light, not the physical law.

RGB color model

The RGB color model is the most popular used color model in computer graphics word. It describes how red, green, and blue light combines at different intensities to produce different colors. This color model is not physical accurate. The main purpose of the RGB color model is calculation performance, therefor most of electronic display adapt RGB color model.

The red, green and blue are primary colors , mixing RGB color will result yellow, cyan, and magenta, which usually been called secondary colors. Mixing secondary color, the result is incorrect.

RGB values encoded in 24 bits per pixel are specified using three 8-bit unsigned integers (0 through 255) representing the intensities of red, green, and blue. Maya calculate color by additive operator, this is not based on any physical principle.

Using 3 lights (red, green, blue) to illuminate a blue sphere, a red sphere and a green sphere. Because the way light shader interactive with surface shader is multiply, when red and blue light illuminate a green sphere, the illuminate area is black.

HSV color model

HSV stands for hue, saturation. Hue is the aspect of discretion of color as names such as red, yellow, etc, it corresponds to the pure colors of the rainbow.

value. Maya implementing these spaces use a approximation to calculate the value of saturation.

Value is the amount of black mixed with the hue to make it darker. If the Value is 0 (zero), then the color is black, regardless of the values for Hue and Saturation.