What is the difference between local/direct and global/indirect lighting?
What does Lambert’s law state?
What is the assumption?
Directional vs point vs spot light
shading (c) of a surface point is proportional to the cosine of the angle between surface normal (n) and direction of the light source (l)
LIght source is realtively far away from the surface (at best infinity)
Source infinite far away, describe only by direction -> directional light
Light source has position -> point light
Point light with restricted solid angle -> spot light
What are the key principles of the Lambertian (diffuse) shading model?
Weil n*l < 0 heißt dass das objekt vom Licht weg ist. Diese sind dann einfach schwarz
What is the ambient component in shading, why do we need it, and how is it computed?
What is flat shading, how does it work, and what are its main drawbacks?
Definition: Shade each triangle as a single flat color by using that triangle’s face normal to compute c.
How it works:
Compute the lighting/shading equation once per triangle (using its normal).
Fill every pixel of that triangle with the same color.
Drawbacks:
Surfaces appear faceted or “blocky.”
Requires a very high triangle count for smooth appearance.
Higher geometric resolution hurts performance.
What is Gouraud shading, how does it work, and what are its main pros and cons?
Method:
Compute an averaged normal at each vertex.
Shade each vertex once (get a vertex color).
Interpolate those colors across each triangle’s pixels.
Pros:
Smoother look than flat shading with fewer triangles.
Cheap per-pixel cost (just color interpolation).
Cons:
Specular highlights can get lost or look wrong.
Still depends on mesh resolution for detail.
What is the purpose of Phong shading, and how is its specular term computed?
How does the Phong exponent p affect specular highlights?
What is the half-vector approximation in Phong shading, and why use it?
What problem does Phong normal interpolation solve compared to Gouraud shading?
Gouraud shading computes lighting per-vertex and interpolates final colors—this can miss or smear out specular highlights on coarse meshes.
Phong normal interpolation instead interpolates normals per-pixel, then applies the lighting model, delivering smooth, accurate highlights without huge triangle counts.
How do you compute the interpolated normal at a pixel in Phong normal interpolation?
How do real‐time CG systems combine ambient, diffuse, and specular components into a single shading equation?
Can our graphics card in real time with our current formula as well handle other more complex reflections
No for now it can just handle isotropic reflections, but not e.g. anisotropic ones
What is a BRDF and what does it describe?
What two fundamental physical requirements must any BRDF satisfy?
How do BRDF, BSSRDF, BTDF, and BSDF differ?
BRDF: Models surface reflection only, at the same point where light arrives.
BSSRDF: Extends to subsurface scattering—light can enter at one point and exit at another.
BTDF: Models transmission (light passing through).
BSDF: A general function combining both reflection (BRDF) and transmission (BTDF).
What is a reflectance lobe, and what do its diffuse and specular shapes represent?
A reflectance lobe is the visualization of a BRDF for a fixed incoming light direction, showing reflected strength in every outgoing direction.
Diffuse part: a roughly spherical lobe (matte baseline scattering).
Specular part: a narrow ellipsoidal spike (shiny highlight around the mirror angle).
The combined lobe describes the material’s overall reflectance pattern.
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