Appearance prediction and appearance engineering both rely on accurate physics-based models of light interaction with scattering properties of 3D object surfaces. Although an object's appearance can be purposefully influenced by configuring its shaping and surface properties, its manifested appearance is also determined by typically ill-controlled variables such as viewpoint and illumination. These points are widely understood. Nevertheless, a point not widely appreciated is that an appearance prediction capability does not equate to an appearance engineering capability; appearance prediction takes the design configuration as a given. Although a design configuration for a singular viewpoint and illumination might be obtained by manual iteration using a prediction framework, such an approach is hopeless for achieving a design that best manifests the desired appearance over a range of viewing situations.
Under aerospace industrial and government sponsorship, Aerodyne has developed a physics-based computer-aided appearance engineering tool, known as "CMO" (for Colorant Mapping Optimizer). Out-of-the-box, it performs 3D materials-based camouflage design. CMO operates using a palette of "colorants" (each possessing full BRDF description, and potentially non-equilibrium light-emitting characteristics such as fluorescence), and assigns colorants to a 3D object's surfaces, to optimize various measures of visibility. It solves the problem of determining what fixed coating scheme (if any) achieves given desired appearances under various viewing/illumination situations, using (a) coating selection; and (b) coating placements as its degrees of freedom (for fixed non-dynamic coating scheme).
We delineate 3 distinct realms of CMO application: (1) conspicuity minimization (camouflage); (2) conspicuity maximization; and (3) desired appearance-matching. For example, under (2), we envision application to the design of optimal visibility signage, navigation aids, etc. Under (3), we envision application to design of physical material surface schemes to manifest desired appearances (under various viewing/illumination situations). This appears increasingly desired for matching physical packaging to virtual depictions in e-commerce, architectural lighting/coloring, theatrical set design, etc.