Brdf1

Keywords: BRDF

Summary

This scene demonstrates use of the various options for attributing objects with bidirectional reflectance distribution function (BRDF) surface properties.

Details

This scene contains a series of example materials that have examples for configuring a variety of diffuse (Lambertian) and specular materials. These material configurations include examples of the following:

The Mirror radiometry solver.
The Shell Target model.
The Ward model.

Important Files

This section highlights key files important to the simulation.

Geometry

The geometry of the scene is completely defined in the geometry\demo.odb file using built-in geometry primitives (boxes, spheres, cylinders, etc.).

Materials

The materials are described in the materials/demo.mat file. The table below summarizes the materials used in the scene:

Table 1. BRDF Materials
ID	Material	Rad Solver	BRDF Model
2	Perfect Reflector	Mirror	N/A
10	Lambertian White	Simple	Ward
11	Lambertian Black	Simple	Ward
500	Glossy Red Paint	Simple	Shell Target (method=0)
510	Glossy Red Paint	Simple	Shell Target (method=1)
520	Glossy Red Paint	Simple	Shell Target (method=2)
600	Gold, shiny	Simple	Shell Target (method=0)
610	Gold, slightly dull	Simple	Shell Target (method=1)

The "Perfect Reflector" material uses the specialized Mirror radiometry solver, which models a perfect mirror. As such, it does not need any surface material properties defined.

The lambertian materials use the Ward BRDF to described spectrally flat reflectors that have no specular component.

The variants of the "glossy red paint" and "gold" use the Shell Target BRDF model to describe more complex BRDFs. The various variants are differentiated by the spectral interpolation method, which is discussed in greater detail here.

All of the materials (except the mirror-like material) use the Simple radiometry solver with the "low" setting, which does a good job of capturing the contributions of these well behaved BRDFs.

Setup

There are two simulation scenarios in this demo:

A single-frame simulation
A multi-frame (video) simulation

Running the Single-Frame Simulation

This single-frame simulation produces a single image file. To run the simulation, perform the following steps:

Run the DIRSIG demo.sim file
Load the resulting demo-t0000-c0000.img file in the image viewer.

Running the Multi-Frame Simulation

The multi-frame simulation produces 41 image files. To run the simulation, perform the following steps:

Run the DIRSIG video.sim file
Load the resulting demo-t0000-c0000.img, demo-t0000-c0001.img, etc. files in the image viewer.

Results

Single-Frame Simulation

The single-frame simulation produces the single-frame simulation shown below:

Figure 1. Output of the single-frame simulation (two percent scaling).

Multi-Frame Simulation

The output of the multi-frame simulation is 41 individual image files. The frames can be scaled and encoded into a video format for viewing using a variety of 3rd party software tools (ffmpeg, mpeg_encode, etc.).

Figure 2. Animation of the multi-frame "spin" collection.