<p>Forward ray-tracing means that rays starts from the light source and are traced towards the eye (light-surface-eye), this is a highly inefficient but accurate method. Reverse raytracing is simply starting in the eye and then trace them towards the light source. These are two classes of ray tracers.</p>

<blockquote>
  <p>Ray casting is the use of ray-surface intersection tests to solve a variety of problems in computer graphics and computational geometry. The distinction is that ray casting is a rendering algorithm that never recursively traces secondary rays, whereas other ray tracing-based rendering algorithms may do so. </p>
</blockquote>

<p>Ray-marching is an implementation of a ray tracer, often used to visualize volumes. Normally ray casting uses a formulae to determine the point of intersection with the surface. In ray marching such a function is not required, instead the intersection is evaluated at several points along the ray. Either these points have a fixed distance between them or every iteration the distance to the next point is based on the distance to the closest surface.</p>

<p>The difference between those are that ray-tracing is a concept to solve the rendering equation, in the end resulting in a certain color for each pixel. Forward and reverse ray-tracing are classes of ray-tracers, ray-casting is a simple algorithm to do ray-tracing and ray-marching is another algorithm to do ray-tracing. As by the comment many other algorithms have been developed to solve the problem with different advantages and disadvantages.</p>

CC BY-SA 3.0
2015-08-13T07:36:10.913Z
related: http://computergraphics.stackexchange.com/questions/161/what-is-ray-marching-is-sphere-tracing-the-same-thing
jozxyqk
CC BY-SA 3.0
2015-08-13T00:20:04.227Z
2015-08-13T00:20:04.227Z
Maurice
<p>There are a number of terms for rendering techniques based on the particle model of light: forward ray-tracing, reverse ray-tracing, ray-casting, ray-marching, and possibly others.  What's the difference between them?</p>

CC BY-SA 3.0
2015-08-25T20:29:11.020Z
I vote to close this question, because it is too broad. There are simply too many variants, especially when including *possibly others* like the ones [Alan Wolfe named in his comment](http://computergraphics.stackexchange.com/questions/225/ray-based-rendering-terms#comment339_225). More specific/narrow questions that compare a few techniques e.g. to achieve a specific goal could very well be suited for this format.
Nero
CC BY-SA 3.0
2015-08-26T10:27:57.190Z
I would split this question to a few more questions.. We already have a pretty good answer for [ray-marching](http://computergraphics.stackexchange.com/questions/161/what-is-ray-marching-is-sphere-tracing-the-same-thing).
joojaa
CC BY-SA 3.0
2015-08-12T20:11:02.493Z
Some others: photon mapping, sphere tracing, cone tracing
Alan Wolfe
<raytracing><raymarching><terminology>
Ray-based rendering terms
Mark
# Ray-based rendering terms

(Asked by: username_0 on 2015-08-12)

There are a number of terms for rendering techniques based on the particle model of light: forward ray-tracing, reverse ray-tracing, ray-casting, ray-marching, and possibly others. What's the difference between them?

**Tags:** raytracing, raymarching, terminology

> **Comments:**
> **username_3**: Some others: photon mapping, sphere tracing, cone tracing  
> **username_1**: I vote to close this question, because it is too broad. There are simply too many variants, especially when including *possibly others* like the ones [username_3 username_3 named in his comment](http://computergraphics.stackexchange.com/questions/225/ray-based-rendering-terms#comment339_225). More specific/narrow questions that compare a few techniques e.g. to achieve a specific goal could very well be suited for this format.  
> **username_2**: I would split this question to a few more questions.. We already have a pretty good answer for [ray-marching](http://computergraphics.stackexchange.com/questions/161/what-is-ray-marching-is-sphere-tracing-the-same-thing).  

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## 1 answers

### Answer by username_4 on 2015-08-13. Score: 4

Forward ray-tracing means that rays starts from the light source and are traced towards the eye (light-surface-eye), this is a highly inefficient but accurate method. Reverse raytracing is simply starting in the eye and then trace them towards the light source. These are two classes of ray tracers.

> Ray casting is the use of ray-surface intersection tests to solve a variety of problems in computer graphics and computational geometry. The distinction is that ray casting is a rendering algorithm that never recursively traces secondary rays, whereas other ray tracing-based rendering algorithms may do so.

Ray-marching is an implementation of a ray tracer, often used to visualize volumes. Normally ray casting uses a formulae to determine the point of intersection with the surface. In ray marching such a function is not required, instead the intersection is evaluated at several points along the ray. Either these points have a fixed distance between them or every iteration the distance to the next point is based on the distance to the closest surface.

The difference between those are that ray-tracing is a concept to solve the rendering equation, in the end resulting in a certain color for each pixel. Forward and reverse ray-tracing are classes of ray-tracers, ray-casting is a simple algorithm to do ray-tracing and ray-marching is another algorithm to do ray-tracing. As by the comment many other algorithms have been developed to solve the problem with different advantages and disadvantages.

> **Comments:**
> **username_5**: related: http://computergraphics.stackexchange.com/questions/161/what-is-ray-marching-is-sphere-tracing-the-same-thing  

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