# TriBar1

Keywords:

## Summary

This demo contains a bundled object version of a USAF Resolution Target. This object can be easily inserted into other scenes and used to to characterize the resolution of the sensor imaging the scene. This demo also includes examples of using the point spread function (PSF) option built into the BasicPlatform plugin.

## Details

The USAF resolution target contains a series of Ronchi mask (high contrast, square wave) targets as black stripe triplets. For this reason, the target is frequently referred to as the USAF "tri bar" target. The sizes of the 6 triplet sets used in the target panel follow a specific mathematical formula (see MIL-STD-150A).

The panel in the bundled object is 1 meter x 1 meter. Since the object is exactly 1 meter wide, it can be easily scaled to any size when it is instanced into a scene GLIST file.

## Important Files

This section highlights key files important to the simulation.

### The Bundled Object

The bundled color checker object is in the `geometry/bundles/tribar` folder. Within that folder, the following files define the geometry and materials for the object:

`tribar.glist`

  This is the main bundle GLIST that should in instanced into the scene.

`1x1.obj`

  This is the 1 x 1 meter OBJ file for the target panel. It includes a simple UV texture coordinate system that allows the material map for the target to be attached.

`tribar.mat`

  This is the material database that contains the entries for material mapped target and the black (1% spectrally flat, diffuse reflectance) and white (40% spectrally flat, diffuse reflectance) materials. All the materials are configured with the WardBRDF model (100% diffuse, 0% specular).

`maps/usaf_1951_tribar.png`

  This folder contains the 2048 x 2149 material map that defines the black and white regions of the target.

### Platform Files

In addition to the simple `demo.platform` file, there are three alternative platform files that incorporate a point spread function (PSF) into the simulation. These scenarios zoom into the higher-resolution features of the target to demonstrate the impacts:

`no_psf.platform`

  This scenario does not include a PSF.

`circle_psf.platform` and `psf/airy_psf.png`

  This scenario uses the classic Airy disk PSF pattern associated with a clear, circular aperture.

`hex_psf.platform` and `psf/hex_psf.png`

  This scenario uses the PSF pattern for a single, hexagonal mirror in the James Web Space Telescope (JWST).

`jwst_psf.platform` and `psf/jwst_psf.png`

  This scenario uses the PSF pattern for the entire James Web Space Telescope (JWST).

Important | As described in the manual, the PSF option is an experimental feature that requires hand-editing of the `.platform` file to configure.

## Setup

This section includes any step-by-step instructions for running and visualizing the simulation.

To run the simulation, perform the following steps:

1. Run the DIRSIG `demo.sim` file

2. Load the resulting `demo.img` radiance file in the image viewer.

The alternative PSF simulations can be run using the respective JSIM files (see `no_psf.jsim`, `circle_psf.jsim`, `hex_psf.jsim` and `jwst_psf.jsim`).

## Results

Figure 1. The pan radiance image of the "tri bar" target.
Figure 2. The zoom image of the "tri bar" target without a PSF.
Figure 3. The zoom image of the "tri bar" target with the circular aperture PSF.
Figure 4. The zoom image of the "tri bar" target with the hexagonal aperture PSF.
Figure 5. The zoom image of the "tri bar" target with the JWST aperture PSF.