What are the considerations for lighting different materials and surfaces

Okay, so I’m building a scale model diorama of a cyberpunk street scene, and I really want the lighting to be realistic. I’m using a mix of materials – corrugated metal for some walls, translucent plastic for holographic signs, painted resin for characters, and even some textured paper for brickwork. I’m also using miniature LED strips and individual LEDs for the lighting.

My main question is, what factors do I need to think about when lighting these different materials so they look believable? For example, I suspect that the shiny corrugated metal will need different lighting treatment than the matte brickwork. And what about the holographic signs? I want them to glow, but not overpower everything else.

Specific things I’m wondering about:

• Reflectivity: How much light will each material bounce back, and how does that impact the overall scene?
• Color Temperature: Does the color of the light need to change based on the material (e.g., warmer light for brick, cooler light for metal)?
• Angle of Incidence: How does the angle at which the light hits a surface affect its appearance? Should I be using diffusers?
• Light Intensity: Will some materials need more intense lighting than others to achieve the desired effect?
• Translucency/Transparency: How do I light translucent materials like the holographic signs so they look like they’re emitting light, but still show the details underneath?
• Textured Surfaces: How do I highlight the texture of the brickwork or the corrugated metal with light?

Basically, I want to avoid making everything look flat and unrealistic. I’m looking for practical advice and examples if possible! Thanks in advance!

Answer

When lighting different materials and surfaces, several factors influence the final result. The interaction of light with a surface depends on the material’s inherent properties, its texture, shape, and the surrounding environment. Lighting considerations must take all of these into account. Here’s a detailed breakdown:

1. Material Properties:

• Reflectance: This is the most fundamental property. It describes the proportion of light that a surface bounces back.
  • High Reflectance: Materials like mirrors, polished metals, and white glossy surfaces reflect a large percentage of light, creating bright highlights and strong reflections. They require careful lighting to avoid glare and hotspots. The angle of incidence equals the angle of reflection for specular surfaces.
  • Low Reflectance: Dark or matte surfaces absorb more light than they reflect, appearing darker and less luminous. They require more light to be adequately illuminated and may need fill lights to reveal details in shadows.
• Specularity: This refers to how mirror-like a surface is.
  • Highly Specular: Surfaces like polished metal, glass, and water create sharp, distinct reflections of light sources and the surrounding environment. Lighting needs to be positioned to create aesthetically pleasing reflections or to minimize unwanted ones. Think about the "angle of incidence equals angle of reflection" rule.
  • Diffuse: Matte surfaces scatter light in all directions, resulting in soft, less defined reflections. These surfaces are more forgiving in terms of lighting placement and are less prone to glare.
• Translucency: This describes how much light passes through a material without being completely transparent.
  • Highly Translucent: Materials like frosted glass, thin fabrics, and some plastics allow a significant amount of light to pass through, creating a soft, diffused glow. Backlighting or internal lighting can be very effective. The thickness and density of the material influence the amount and diffusion of the transmitted light.
  • Opaque: Opaque materials do not allow light to pass through. Their appearance is solely determined by reflected light.
• Subsurface Scattering (SSS): This is the phenomenon where light enters a material, scatters internally, and exits at a different point.
  • Materials like skin, wax, marble, and some plastics exhibit SSS, creating a soft, glowing appearance. Realistic rendering of these materials requires specialized lighting techniques that simulate the internal scattering of light. The color and density of the material affect the amount and distance of scattering.
• Refraction: This is the bending of light as it passes from one medium to another (e.g., air to water or air to glass).
  • Transparent materials like glass and water refract light, creating distortions and caustics (patterns of focused light). Lighting for these materials should account for the refractive index of the material and the angles at which light passes through it.
• Color: The color of a material affects the color of the reflected light. A red surface will primarily reflect red light and absorb other colors. The color of the light source also influences the perceived color of the material.
• Texture: The surface roughness of a material affects how it reflects light.
  • Rough Surfaces: Scatter light more diffusely, reducing specular highlights and creating softer shadows.
  • Smooth Surfaces: Reflect light more specularly, producing brighter highlights and sharper shadows.
• Fluorescence/Phosphorescence: Some materials absorb light at one wavelength and emit it at a different wavelength. This can create a glowing effect. Specialized light sources (e.g., UV light) may be required to activate these properties.

2. Lighting Techniques and Considerations:

• Direction of Light: The angle at which light strikes a surface significantly impacts its appearance.
  • Front Lighting: Illuminates the front of the object, minimizing shadows and flattening the appearance.
  • Side Lighting: Creates strong shadows and highlights, emphasizing texture and form.
  • Backlighting: Illuminates the object from behind, creating a silhouette effect.
  • Top Lighting: Can create dramatic shadows and highlight the upper surfaces.
  • Bottom Lighting: Is less common, but can create an unnatural, dramatic effect.
• Intensity of Light: The brightness of the light source affects the overall brightness and contrast of the scene.
  • High Intensity: Can create harsh shadows and blown-out highlights.
  • Low Intensity: Can result in a dim, flat image with little contrast.
• Color Temperature: The color of the light source (measured in Kelvin) affects the perceived color of the materials.
  • Warm Light (low Kelvin): Creates a yellowish-orange tint.
  • Cool Light (high Kelvin): Creates a bluish tint.
• Type of Light Source:
  • Point Light: Emits light from a single point, creating hard shadows.
  • Directional Light: Emits parallel rays of light, simulating sunlight and creating hard shadows.
  • Area Light: Emits light from a larger surface, creating soft shadows.
  • Ambient Light: Provides a general, non-directional illumination, filling in shadows.
• Shadows: Shadows define the form and texture of a material. The softness or hardness of shadows depends on the size and type of light source.
• Reflections: Reflections can add realism and depth to a scene, but they can also be distracting or create unwanted glare.
• Light Placement: Precise light placement is crucial for achieving the desired effect. Consider the angle of incidence, the distance from the light source to the object, and the use of reflectors or diffusers.
• Fill Lights: Used to soften shadows and reveal details in dark areas.
• Specular Highlights: These are the bright reflections of light sources on shiny surfaces. Their size, shape, and intensity depend on the specularity of the material and the type of light source.

3. Specific Material Examples:

• Metals (Polished): Requires careful positioning of lights to control reflections. Use large, soft light sources to create broad highlights or smaller, focused lights for sharper reflections.
• Metals (Matte): Less reflective than polished metals. Side lighting can reveal surface imperfections and texture.
• Glass: Lighting needs to account for refraction and reflections. Backlighting can emphasize the transparency of the glass. Caustics can be created by focusing light through the glass.
• Water: Creates complex reflections and refractions. Caustics are particularly noticeable. The surface texture of the water (e.g., ripples) affects the way light is scattered.
• Skin: Requires careful attention to subsurface scattering. Soft, diffused light sources are generally preferred.
• Cloth: The texture and weave of the cloth affect how it reflects light. Backlighting can reveal the translucency of thin fabrics.
• Wood: Side lighting can emphasize the grain and texture of the wood. The finish (e.g., polished, matte) affects the specularity.
• Stone: Often has a rough, uneven surface. Side lighting can reveal the texture and imperfections of the stone.

4. Environmental Considerations:

• Ambient Lighting: The existing light in the environment affects the overall lighting scheme. Consider the color and intensity of the ambient light when placing and adjusting light sources.
• Surrounding Objects: Nearby objects can reflect light onto the subject, affecting its appearance.
• Color of Walls and Surfaces: Colored walls can tint the reflected light, affecting the perceived color of the subject.

In Summary:

Lighting different materials and surfaces is a complex process that requires careful consideration of the material’s properties, lighting techniques, and the surrounding environment. Experimentation and observation are key to achieving the desired results. Understanding how light interacts with different materials is crucial for creating realistic and visually appealing images.