4 5 BILLBOARDING Using billboards within games BILLBOARDS

4. 5. BILLBOARDING Using billboards within games

BILLBOARDS Using billboards within games

Billboarding is a rendering technique that orientates some object (typically a texture mapped quad) towards a defined target (typically the camera). Billboarding The orientation may be constrained to be along a certain axis.

Billboarding is of use as it provides a means of reducing the number of polygons that need to be rendered. This is done by replacing (potentially complex) 3 d geometry with an imposter texture. This is not a new technique!

Billboarding

Two types of billboarding are commonly encountered: Common type of billboarding Cylindrical The rotation of the object is restricted to a vector, usually along the positive direction of the Y axis. Spherical No restriction to the orientation of the object is imposed

Billboards: Trees and Vegetation The visual complexity of grass, shrubs, trees, etc. is such that it is often rendered using one or more billboards.

Billboards: Clouds Overlapping billboards provide a very powerful technique for rendering clouds (which cannot be easily defined in terms of a mesh)

Video not available in on-line slides

Billboards: Explosions Blending together a number of billboards within a set of

within the scene as separate images, it becomes possible to render the image (as a billboard) instead of the 3 D object, i. e. the imposter is a simplified representation of a complex 3 D object. Billboards: Imposters Dynamically-generated imposters are regenerated at runtime by rendering an image of a 3 D object to a texture.

Volumetric billboards use volumetric images of an object stored into 3 D textures, instead of 2 D images as for standard billboards. Volumetric Billboards A rendering approach can visually reconstruct the object, offering parallax effects, reduced popping artefacts, etc.

Video not available in on-line slides

ed ect r i g D din a e r DIRECTED READING Directed reading concerning billboarding

billboards. • Read Real-Time Cloud Rendering for Games – for an exploration of cloud rendering using billboards. Directed reading: • Read Rendering Forest Scenes in Real-Time – for details on reducing large forest scenes using billboards. • Read Spherical Billboards and their Application to Rendering Explosions – for information on how spherical billboards can be used for explosions. ed ect r i g D din rea

on volumetric billboard creation/rendering. • Read Billboard Clouds for Extreme Model Simplication – for information on using a “billboard cloud” as a means of simplifying a 3 D object. Directed reading: ed ect r i g D din rea • Read Dynamic 2 D Imposters: A Simple, Efficient Direct. X 9 Implementation – for information on how to implement dynamic imposters at: http: //www. gamasutra. com/view/feature/2501/dynamic_2 d_imposters_a_simple_. php

Summary Today we explored: ü The variety of uses that billboarding offers within games. : o d o T cted e r i d e h t d a e üR reading like d l u o w u o y f üThink i y n a t n e m e l p m to i ding r a o b l l i b f o t c aspe ct? e j o r p r u o y n withi