16 - Misc Rendering - Procedural, Particle, Volumetric

ucla | CS 174A | 2024-03-19 16:16

Opacity

introduce oopacity intensity 0-1 as $α$
apply this to color channels by multiplying over
Composition of colors
layered polys can be composited colors based on opacity
straight - factor out opacity, just get composite color
pre-multiplied - assuming colors given after opacity multiplied, find olor aand alpha w saame algo

rendered as sprites, display color based on z-buffer or sprite which ever is on top render sprites (particles) always facing the front/camera

tesselation make “hollow” objects
volume rendering allows us to make “solid” objects that can be sliced and can be “entered”
usually nothing but ray casting (non-recursive) and parallel projection
discretize volumetric objects to elements called “voxels”
- each voxel can store some properties (scalars)
- stored a small changes in the coordinate system
- usually naturally ordered
- Marching Cubes (Volumetric Rendering Algo)
makes a poly mesh of iso-surfaces by looking at voxel coords
iso surfaces in voxels:
e.g. 2D marching squares, check if the color or other property is greater than a threshold, then determine the cases to render
- Splatting Method
“splat” the front facing (bc no PS) voxels of the object and composite (FTB or BTF) and splat it onto the screen to generate the footprint of the volumetric object
V-buffer
ray cast from eye through volume
trilinear interp for properties of non-vertex location of a voxel
accumulate color and opacity as ray passes through the volume
parallel ray cast through each pixel (in parallel), choose t as sampling rate to determine how many voxels along the ray you will sample
color composition is done FTB so no backface culling, just do composition above
determine color using composition aalgo
where the transfer function can be specified
Optimization