PATH TRACING Flashcards
What sort of shadows does the whittard algorithm make
Very crisp and well defined edged shadows
What are the properties of shadows in real life
Umbra - dark area in the middle
Penumbra - edge which is less well defined
no crisp edges
Why is the penumbra created
Because in the real world, light is not a point but an area
An area light will mean some light gets through but some isn’t (around the edge of an object)
What is the Monte Carlo technique
Using a statistical rather than an analytical or brute force approach
Eg estimating how many rays from a source will get blocked by an object by just testing with a small number to find a ratio
We can approximate an area of a shape by placing it in a known area and firing dots and calculating how many land on the shape and how many do not
How is path tracing different to ray tracing
We are only interested in one possible path for the primary ray each time
How do we carry out path tracing
We just pick a random ray coming from the viewpoint and follow it to a point on the chosen surface and then follow the rebound ray
We are only interested in one path for the primary ray to the surface
We rely on the fact that we are shooting enough primary rays off so we will eventually get an accurate picture
We have to fire a LOT of primary rays
This means we are sampling uniformly and randomly in the hemisphere created around the surface normal of the chosen surface
What is the unit for rays sent into the scene for path tracing
Samples per pixel (SPP)
Insufficient SPP will result in noisy and innacurate scenes
Increasing SPP increase the time needed to render - computationally expensive
What is caustics
light patterns formed when rays of light are reflected or refracted by a curved surface
swimming pool/glass of water
what is Fluorescence and Phosphorescence
emission of light by a substance after it absorbs photons
Fluorescence is the immediate emission of light upon absorption of photons
Phosphorescence involves delayed emission, with the release of light occurring after a delay
What is doppler effects
refers to the change in frequency or wavelength of a wave in relation to an observer moving relative to its source
A redshift occurs when the light source is moving away from the observer
Blueshift occurs when it is moving towards the observer
Commonly observed in astronomy to study the motion of celestial objects
What is participating media
materials that interact with and scatter light as it passes through them
Commonly seen in effects like fog, smoke, or underwater scenes in visual arts
What are the visual effect naturally created by pathtracing
soft shadows, depth of field, motion blur, caustics, ambient occlusion, indirect lighting
