lecture 15 Flashcards
a primitive in visual rendering is formed by what
one or more vertices
vertices are not
grid aligned
all primitives are merged to produce what
2d pixels on the display
what two things does the rendering process user
visibility problem and shading combined
what two things are involved with the visibility problem
recasting and rasterization
what is raytracing
image order rendering: loops over pixels, then over triangles (grid in front of the triangle that a ray angles to/ doesnt scale , needs very fast rendering),
different shading models (2)
lambert and blinnphong
what is rasterization
object order rendering: loops over triangles and then over pixels, asks if the pixels lies in the triangle (it projects vertices onto grid and thenloops over the pixels
painters algorithm
inefficient for large numbers of objects (object, foreground, trees, image by image rather than which is in a pixle)
zbuffer
looks at two different objects, in the zbuffer depth buffer and in a 3d scene evaluates which objects are in front and then for the projection plane, only renders what is seen from front
texture mapping
render traingles, then base color, then individually pixelate?
bump mappping
alters the surface normal, takes a ball and places a texture on top of it to create an orange like texture
aliasing
not a huge problem fro mdoern displays ~>300ppi, but it is for vr because eyes are so close to the screen
counteract aliasing
hardware line then prefiltering box then prefiltering gaussian which blurs the edges
mipmapping
takes a texture and renders it at different sizes and places them at different depths to give illusion
3 types of culling
view frustrum, occlusion, back face
view frustrum culling
see images in periphery
occlusion culling
they are behind the images in front
back face
they only have one side rendered, point away, can also be front face and point towards
3 vr rasterization probems
aliasing problem because vr displays dont have high pixel density and provide mistmatch movement, magnified by setero perception, stereovision makes texutre mapping look fake
correct distortions
barrel/pincushion distortion, correct using fresnel lens because more accuratley bends lights
latency diagram with 6 steps
input, usb, engine, write display, pixel switching, new images
high latency causes what 3 problesm
reduce presence, cause vr sickness, inefficient interaction
6 remedies for high latency
lower complextiy, improve rendering pipeline performance, remove pipleine delays, user prediction to estimate future viewpoints, shift/disort rendered image to compesnate for missig frames, faster phones, image warping
