Computer Graphics: Principles and Practice
John F. Hughes, James D. Foley, Andries van Dam, Steven K. Feiner
11 flashcards · Computer Science · by lakesare
What's this?
This is a stencil (both the sheet of metal and the resulting image). The stencil is both the resulting image or pattern and the intermediate object; the context in which stencil is used makes clear which meaning is intended. Stencilling produces an image or pattern by applying pigment to a surface under an intermediate object with designed gaps in it which create the pattern or image by only allowing the pigment to reach some parts of the surface. In practice, the (object) stencil is usually a…
What do dpi and ppi stand for?
dots per inch pixels per inch Number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm). Similarly, the more newly introduced dots per centimeter (d/cm or dpcm) refers to the number of individual dots that can be placed within a line of 1 centimeter
Name 2 meanings of the resolution of the display.
total number of pixels - e.g. LCD monitor with 2560 × 1440 resolution dpi - dots per inch (or ppi - pixels per inch) DPI is primarily a print measurement, as the measurement doesn’t seamlessly transfer to digital media. When DPI is used for print, the standard is 300DPI, as it presents the best quality image.
What's a screw eye?
Screw eyes are a screw with a loop on one end and threads on the other end. Screw eyes are commonly used to attach cables to objects, for instance attaching a string to the back of a painting to allow the painting to hang from a nail on a wall.
Where is the viewer eye position? In 1525, Albrecht Dürer made a woodcut demonstrating a method by which one could create a perspective drawing of almost any shape (this is a lute).
Where the string passes through the screw eye on the wall. The drawing is a perspective view of the lute, showing the way the lute would look to a viewer whose eye was at the screw eye. Note that the height of the screw eye on the wall and the position of the table can both be changed, so the relative positions of the viewpoint and the drawing should be regarded as parameters of this scene-rendering engine.
What's temporal VS spatial aliasing?
temporal aliasing - when occurs in signals sampled in time, for instance digital audio. spatial aliasing - when occurs in spatially sampled signals (e.g. moiré patterns in digital images).
Why does the wagon-wheel effect happen?
In recorded media, the effect is a result of temporal aliasing. The wagon-wheel effect is most often seen in film depictions of wagons in Western movies, although recordings of any regularly spoked rotating object will show it, such as helicopter rotors, aircraft propellers and car commercials. It can also commonly be seen when a rotating wheel is illuminated by flickering light. These forms of the effect are known as stroboscopic effects: the original smooth rotation of the wheel is visible on…
What's this function's Fourier transform? f(x) = 2.1 cos(x) − 3.5 cos(2x) − 8 cos(3x) Summing up periodic functions (in color) of different frequencies leads to more complicated functions, in this case the black (thickest) one.
g, is the function with g(1) = 2.1, g(2) = −3.5, and g(3) = −8
Fourier transform VS Taylor series?
Fourier transform - enables one to express a periodic function as an infinite sum of trigonometric functions (sines and cosines). Taylor series -enables one to express a function as an infinite sum of powers. Finally, in practice one wants to approximate the function with a finite number of terms, say with a Taylor polynomial or a partial sum of the trigonometric series, respectively. In the case of the Taylor series the error is very small in a neighbourhood of the point where it is computed,…
What's an ad hoc hypothesis?
In science and philosophy, ad hoc means the addition of extraneous hypotheses to a theory to save it from being falsified. Ad hoc hypotheses compensate for anomalies not anticipated by the theory in its unmodified form. Scientists are often skeptical of scientific theories that rely on frequent, unsupported adjustments to sustain them. Ad hoc hypotheses are often characteristic of pseudo-scientific subjects such as homeopathy. If someone wants to believe in leprechauns, they can avoid ever bein…
What's a convolution, essentially?
A sum of many displaced copies of the same function. In computing this product, we’re taking four shifted copies of the number 1231, each multiplied by a different 1 from the second factor, summing them; this is essentially a convolution operation. consider how a square occluder, held above a flat table, casts a shadow when illuminated by a round light source. . The brightness at a point P is determined by how much of the light source is visible from P. We can think of this by imagining the squ…