Radiance change with light distance

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SUMMARY

This discussion focuses on the behavior of radiance in the context of Monte Carlo integration for rendering equations. It clarifies that while radiance does not change with distance, this does not imply that a point light source can illuminate objects from an infinite distance. The conversation highlights the limitations of modeling light paths, particularly the computational cost associated with tracing rays and the physical accuracy of reflections between surfaces. Key references include a Stanford course document that discusses the persistence of light quantity associated with rays.

PREREQUISITES
  • Monte Carlo integration techniques in computer graphics
  • Rendering equations and their applications
  • Understanding of light behavior and ray tracing
  • Basic knowledge of computational costs in graphics simulations
NEXT STEPS
  • Study the Stanford course document on rendering equations at Stanford Graphics Course
  • Explore advanced Monte Carlo integration methods for improved rendering accuracy
  • Investigate ray tracing algorithms and their computational efficiency
  • Learn about physical accuracy in light reflection modeling
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This discussion is beneficial for computer graphics developers, rendering engineers, and researchers focused on light simulation and Monte Carlo methods in graphics rendering.

Gadersd
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I am trying to solve the rendering equation with monte carlo integration. I gather all of the incoming radiance from light sources and plug it into the rendering equation. A reference I am using said that radiance does not change with distance. Does this mean that a point light source will illuminate objects from a infinite distance away since the radiance does not change?
 
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Not sure. Can you provide a link to your reference?
 
I can't be sure, but it appears to say that whatever quantity of light you have associated with a ray will stay with that ray. I wouldn't say that a point source can illuminate an object an infinite distance away, since light is not physically composed of rays.
 
In this modelling scenario you are modelling the path of individual rays which may as well be regarded as individual photons for the purpose of intuition, although the amount of energy associated with each ray is likely to be much greater than an actual photon.

Yes the ray will travel infinitely if running the simulation does not introduce an interaction with another object. But what probability is associated with this outcome in your scenario?

The model appears limited by the quantity of light that can be associated with a ray, and also by the physical accuracy of modelling reflections between ideal flat surfaces separated by large distances.

The first limitation is due to the increase in computational cost of tracing more rays, each having less energy associated with it (as ray energy approaches photon energy resolution is improved). The second limitation is due to measuring and encoding accurate curvature.

The first limitation is obvious and tangible. The second is barely of concern for basically all pracital applications.
 
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