INDIRECT VOLUME RENDERING

Question 1

What is indirect volume rendering

Answer 1

Turning volume data into polygons so it can be rendered more quickly
GPUs are good at polygons, pixels and textures
IVR is making use of this

Question 2

What is an isosurface

Answer 2

A 3D version of the isoline

Question 3

What is an isoline

Answer 3

A line which represents a constant value
Eg a contour line
(represents a constant height)

Question 4

What is the marching cube algorithm

Answer 4

Used for generating the surfaces of a 3d object
Uses combinations of triangles - so that we can display the surface as a mesh

Question 5

What is Proxy Geometry

Answer 5

Imagine the colour from the voxels are being splattered like paint onto pains of glass that are stacked one behind the other, so we can see the accumulated image of all the stacked paint splatters

modern GPUs excel at this

Question 6

Mapping between volume and texture coordinates

Answer 6

straightforward
use barycentric interpolation and map that with linear interpolation onto the texture coordinates
The process is the same as in 2D just with an extra dimension
All done in hardware - fast

Question 7

cons with proxy geometry

Answer 7

can sometimes see the gaps between the slices which is not a good rendering

Always want the slices to be parallel to the viewpoint so we cannot see this

Too few slices - confusing mess

more and more slices - content becomes much more clear