# Ray tracing- Is luminance being traced?

• kingsna1
This means that luminance is measured in units of cd/m^2 and is used to measure light perceived by humans.In summary, ray tracing involves mapping out luminance for a scene. With backwards ray tracing, each ray has a luminance value associated with it. For a perfectly diffuse surface, the mean of all the secondary rays' luminance can be used to determine the luminance value for the primary ray. However, this assumption may not always be accurate. In terms of radiometry, rays in a ray trace are associated with radiance, while in photometry, luminance is used to measure light perceived by humans.
kingsna1
My understanding of ray tracing is that it maps out luminance for a scene. Now with ray tracing (backwards ray tracing that starts from the camera outwards) does each ray have a luminance value associated with it? In the case of a perfectly diffuse surface, can one simply take the mean of all of the secondary rays luminance to arrive at a luminance value for the primary ray or is this assumption wrong? If L0 are the primary rays luminance, and L1 ,L2 ,L3, L4 ,L5 are the secondary rays that are created due to the diffuse surface. (see Diagram for explanation).

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Interesting question- in radiometric terms, rays in a ray trace are associated with radiance- a conserved quantity with units of W/(m^2*sr)- the quantity tells you how much power is propagating in a given direction.

Luminance is the photometric equivalent to radiance- radiance that has been corrected for the spectral response of normal human eyes.

## What is ray tracing?

Ray tracing is a rendering technique used in computer graphics to create realistic images by simulating the way light travels and interacts with objects in a scene.

## How does ray tracing work?

Ray tracing works by tracing the path of light rays from a virtual camera through each pixel in a scene, and calculating how the light interacts with the objects in the scene to determine the color and brightness of each pixel.

## What is the purpose of tracing luminance in ray tracing?

The purpose of tracing luminance in ray tracing is to accurately simulate the way light behaves in the real world, resulting in more realistic and visually appealing images.

## What are the limitations of ray tracing?

Ray tracing can be computationally expensive and time-consuming, making it difficult to render complex scenes in real-time. It also struggles with simulating certain lighting effects, such as caustics and global illumination.

## How is ray tracing used in different industries?

Ray tracing is commonly used in industries such as video game development, animation, and architecture to create photorealistic images and videos. It is also used in scientific visualization and virtual reality applications.