Surface Rendering in Computer Graphics with examples

What is Surface Rendering?

• Surface rendering refers to generating 2D images from 3D geometric models.
• Basic illumination is a crucial aspect of surface rendering, as it simulates the interaction of light with surfaces, creating realistic images.

What is Basic illumination?

• Basic illumination refers to the fundamental process of simulating how light interacts with surfaces in a 3D environment to generate realistic images.
• It involves factors such as light sources, material properties, and reflection models.

Light Sources

• In a 3D environment, light sources play a vital role.
• They can be directional, point lights, or ambient lights.
• Directional lights have a specific direction but no definite position.
• Point lights emit light uniformly in all directions from a specific point.
• Ambient lights provide constant illumination across the scene.
• Example: In a virtual room, a directional light might represent sunlight streaming through a window,
• while point lights could simulate lamps, and ambient light contributes to overall scene brightness.

Material Properties

• Surface materials have properties such as ambient reflectance, diffuse reflectance, and specular reflectance.
• Ambient reflectance represents the constant color of an object,
• diffuse reflectance determines how it interacts with direct light and
• specular reflectance accounts for shiny highlights.

Ambient Reflectance

• Ambient reflectance represents the constant color and brightness of an object under ambient or indirect lighting.
• It is the component that ensures that objects are not completely dark, even in the absence of direct light sources.
• Ambient reflectance provides a uniform level of illumination across an object's surface.
• This helps maintain visibility and prevents complete darkness.
• Unlike direct lighting, which varies based on the direction of light, ambient reflectance is independent of light direction.

Diffuse Reflectance

• Diffuse reflectance accounts for how a surface interacts with direct light.
• It determines the color and brightness of a surface based on the angle between the incoming light and the surface normal.
• Example: Imagine a virtual soccer ball on a grassy field under sunlight. The green color of the grass is the diffuse reflectance.
• When sunlight hits the ball, the color and brightness are influenced by how the surface scatters light, creating a realistic appearance.

Specular Reflectance

• Specular reflectance is responsible for the shiny highlights on a surface, especially when illuminated by a direct light source.
• It represents the mirror-like reflection of light.
• It occurs on smooth surfaces like glass, metal, or water.
• Example: Imagine sunlight reflecting off the surface of a calm lake.
• The concentrated, bright reflection of the sun on the water is an example of specular reflectance.
  

Reflection Models

Ambient Lighting

• Ambient lighting contributes to the overall illumination or light of a scene.
• It is a constant light that simulates indirect illumination or light from multiple sources.
• While it helps eliminate dark areas, too much ambient light can lead to unrealistic scenes.

Distance Effects

• The distance between a light source and a surface affects the intensity of illumination or light.
• The inverse square law dictates that as distance increases, the illumination decreases quadratically.
• This distance attenuation is crucial for creating realistic lighting in a 3D environment.

Shading Models

What is Gouraud Shading?

• Gouraud shading is an interpolation technique used to produce smooth shading across polygons.
• Gouraud shading produces visually appealing results and is computationally less expensive than other shading models like Phong shading.
• Gouraud shading may not capture specular highlights and subtle lighting variations as effectively as more advanced models.
• Named after Henri Gouraud, this method calculates vertex colors and then interpolates them across the polygon's surface.
• Color intensity at each vertex is computed based on the lighting model (e.g., Phong reflection model) and material properties.

Phong Shading Model

• The Phong shading model, proposed by Bui Tuong Phong, is an improvement over Gouraud shading, particularly in handling specular highlights.
• The Phong model incorporates three main components: ambient, diffuse, and specular reflection.
• Phong shading excels at capturing highlights and shadows, making it suitable for materials with glossy or shiny surfaces
• Unlike Gouraud shading, Phong shading calculates color intensities at each pixel rather than at the vertices
• Example: Imagine a 3D model of a metallic sphere under directional lighting

Intensity Calculation

Conclusion