---
name: "compamb"
section: "1"
platform: "linux"
package: "radiance"
version: "4R1+20120125-1+b1"
release: "Debian 7 (Wheezy)"
platforms: ["linux"]
url: "https://new.carta.tech/compamb"
---

# compamb(1)

compute good ambient value for a rad input file

## NAME

compamb - compute good ambient value for a rad input file

## SYNOPSIS

**compamb** \[ **-c** \]\[ **-e** \] **rad\_input\_file**

## DESCRIPTION

*Compamb* computes a good ambient value for the specified *[rad(1)](/rad/1.md)* variable file and appends it to the file as a "render= -av" option. If the *-c* option is specified, then *compamb* includes color information in the computed ambient value, rather than estimating a grey value to avoid rendering color shifts. If the *-e* option is specified, then *compamb* also computes a good exposure value for this scene, and appends it to the *rad* file as well.

*Compamb* is a shell script that makes calls to other RADIANCE programs and utilities to do the actual work. A substantial amount of time may be required to complete this script, since *compamb* calls *[rpict(1)](/rpict/1.md)* to render low resolution frames for each view in the *rad* file, setting "QUALITY=High" to compute interreflections. The resulting ambient file is thrown away, since it would disagree with the new -av setting used for the final renderings. This method is preferable to setting the *-aw* option of *rpict,* which frequently results in splotchy artifacts.

## AUTHOR

Greg Ward Larson

## SEE ALSO

[lookamb(1)](/lookamb/1.md), [rad(1)](/rad/1.md), [rpict(1)](/rpict/1.md)