Презентация на тему Image-based Rendering

but also sometimes used as a synonym for icon.
World-aligned

billboards
Cylinderical and spherical
Impostors

Enable alphatest

the viewer
Two kinds:
Cylindrical: for cylindrically symmetric objects (e.g., trees)
Spherical:

for spherically symmetric objects (e.g., smoke)

on XZ plane
View Up is Y-axis
Viewer need not stay

on XZ plane

(n,pxz)
Rotate about localX
φ = acos (pxz,p)
Watch out

for signs of angles

billboard), you want to know where camera is, just

remember that the eye coordinate of the camera is always at the origin [facing –Z]

coord.
During each frame:
Rotate every n into v

various viewing angles
Instead of showing the facet model, show

a polygon with correct texture

object, to avoid repeated binding
Use texture transform to switch

to the correct one
glGetIntegerv (GL_MAX_TEXTURE_SIZE, &size)

object from the current viewpoint into an image texture,

then post on a billboard)

object for which an imposter is generated together with

its bounding box, which is used to bound the extent of the object’s picture. The imposter is chosen to lie in the plane P through the object center C normal to the direction from C to the point of view V (normal to n as shown at the bottom of figure 1). The extent of the imposter is taken as the smallest rectangle in P which contains the projection of the object’s bounding box onto P

to determine size of impostor polygon
Issues
Alignment (texture placement)
Texture resolution
Invalid

impostor (require regeneration)

pixels
Usage:
A few instances of the object
A few frames of

the object (strategy for updating imposters)
Rendering distant objects
Movement of project image diminishes with an increased distance from viewer
Image lowpass filtered to create depth-of-field effect

to reduce the number of cells to draw
One layer

for background, one for middle ground, one for character,…
Background layers need to be changed less frequently than foreground, slow moving less frequently than fast moving,…
Layers are composited as a final step
Coherent layers was designed to work with hardware that supports fast compositing and layer warping
Approach:
Break scene into layers by hand
At run-time, warp some layers, re-render others
Composite the layers into the frame buffer (back to front)

better performance
Partition the scene into a hierarchy of boxes

and create an impostor for each box
Rerendering: done only when one or more of its children’s impostors need to be updated due to movements.