Alternative Diffuse Lighting and Specular Reflection Approach Using YIQ Color Space for 3D Scene Visualization Using Programmable HLSL Shaders

 

Y. Kotsarenko*, F. Ramos

 

Instituto Tecnológico y de Estudios Superiores de Monterrey Campus Cuernavaca Xochitepec, Morelos, México.

 

Abstract

In this work an alternative approach for diffuse lighting and specular reflections is presented that uses YIQ color space instead of traditional RGB color space. The classical illumination algorithms that rely on RGB color space may lead to unrealistic results either due to the fact that they cannot make the original color brighter (inherent limitation imposed by using the RGB color space) or produce incorrect shades when viewed from certain angles because in the calculation of the specular reflection the original texture color is not taken into account.

The approach proposed in this work gets around the problem by applying illumination in YIQ color space using its "luma" component (Y). In this novel approach the diffuse lighting is capable of increasing the perceived brightness of the source texture and the resulting color is always dependant on the surface's texture and produces reasonably realistic results when viewed from any possible angle. The algorithm and its HLSL shader code are described in this work along with the experiments that illustrate the problem and the solution. The performance benchmarks are also provided, showing that the proposed approach is a viable and realistic solution for applications running in real-time.

Keywords: visualization, illumination, shaders, lighting, reflection.

 

Resumen

En este trabajo se presenta un nuevo enfoque para iluminación difusa y reflexiones especulares que utiliza el espacio de color YIQ en vez del tradicional RGB. Los algoritmos clásicos de iluminación que utilizan el espacio de colores RGB pueden generar resultados no realísticos ya sea porque no pueden hacer el color de la textura original más brilloso (limitante que se origina por utilizar el espacio de color RGB) o pueden producir un tinte incorrecto en ciertos ángulos porque el cálculo de la reflexión especular no toma en cuenta el color de la textura original.

El enfoque propuesto evita los problemas anteriormente mencionados aplicando la iluminación en el espacio de colores YIQ utilizando el componente de "luma" (Y). Con este enfoque novedoso en la iluminación difusa se puede incrementar el brillo perceptual de un color, el cual siempre depende de la textura original. Por lo tanto, el resultado se ve razonablemente realístico desde cualquier ángulo. El algoritmo y su código fuente HLSL están descritos junto con los experimentos que muestran el problema y el resultado. Además, las pruebas de desempeño también están adjuntas mostrando que el enfoque propuesto es una solución viable y realística para aplicaciones corriendo en tiempo real.

 

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