# Surface Ray Tracing

![](https://894783789-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LPHXQ1I3gb93zpLrLZf%2Fuploads%2Fgit-blob-3df032a0948e396b07144cc4a2aa7e33e785ed3a%2FSurface_Ray_Tracing.png?alt=media)

![](https://894783789-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LPHXQ1I3gb93zpLrLZf%2Fuploads%2Fgit-blob-aa1356e1a0b8311925fe703236490cb7c0fcb0b7%2FSurface_Ray_Tracing.png?alt=media) - [\[source code\]](https://github.com/ladybug-tools/ladybug-grasshopper/blob/master/ladybug_grasshopper/src/LB%20Surface%20Ray%20Tracing.py)

Get a ray tracing visualization of direct sunlight rays reflected off of *source\_geo and subsequently bouncing through a set of context* geometries.

Examples where this visualization could be useful include understading the reflection of light by a light shelf or testing to see whether a parabolic glass or metal building geometry might focus sunlight to dangerous levels at certain times of the year.

Note that this component assumes that all sun light is reflected specularly (like a mirror) and, for more detailed raytracing analysis with diffuse scattering, the Honeybee Radiance components should be used.

### Inputs

* **vector \[Required]**

A sun vector (typically from the "LB SunPath" component), which will be used to evaluate the light boucing off of the *source\_geo and through the context*.

* **source\_geo \[Required]**

A brep or mesh representing a surface off of which sun rays first bounce. Lists of breps or meshes are also acceptable. These surfaces will be used to generate the initial sun rays in a grid-like pattern.

* **context**

Breps or meshes for conext geometry, which will reflect the sun rays after they bounce off of the \_source\_geo. They can also block the sun rays to the *source\_geo if context\_block* is set to True.

* **receiver**

Optional breps or meshes for receiver geometry for which sun ray intersection is being studied. If specified, only sun rays that reflect off of the \_source\_geo and have their last bounce intersect this receiver within the *last\_length* distance will appear in the result. This can help filter results to only an area of intersect where the impact of reflected sun rays is a concern.

* **grid\_size \[Required]**

A positive number in Rhino model units for the average distance between sun ray points to generate along the \_source\_geo.

* **bounce\_count**

An positive integer for the number of ray bounces to trace the sun rays forward. (Default: 1).

* **first\_length**

A positive number in Rhino model units for the length of the sun ray before the first bounce. If unspecified, this will be the diagonal of the bounding box surrounding all input geometries.

* **last\_length**

A positive number in Rhino model units representing the length of the sun ray after the last bounce. If unspecified, this will be the diagonal of the bounding box surrounding all input geometries.

* **context\_block**

Set to "True" to count the input \_context as something that fully blocks rays as opposed to having the rays simply bounce off of it. This can be particularly useful in cases with lots of rays where you are only concered about the rays that can actually hit the \_source\_geo. (Default: False).

* **run \[Required]**

Set to "True" to run the component and perform the ray tracing study.

### Outputs

* **report**

Reports, errors, warnings, etc.

* **rays**

A list of polylines representing the sun rays traced forward onto the *source\_geo and then through the context*.

* **int\_pts**

A data tree of intersection points one one branch for each of the rays above.


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