4.5. BILLBOARDINGUsing billboards within games

BILLBOARDSUsing billboards within games

Billboarding

Billboarding is a rendering technique that orientates some object (typically a texture mapped quad) towards a defined target (typically the camera).

The orientation may be constrained to be along a certain axis.

BillboardingBillboarding 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) 3d geometry with an imposter texture.

This is not a new technique!

Billboarding

Common type of billboarding

Two types of billboarding are commonly encountered:

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: CloudsOverlapping 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: ExplosionsBlending together a number of billboards within a set of particle effects can produce impressive explosions effects.

Billboards: Imposters

By capturing and representing 3D objects within the scene as separate images, it becomes possible to render the image (as a billboard) instead of the 3D object, i.e. the imposter is a simplified representation of a complex 3D object.

Dynamically-generated imposters are regenerated at runtime by rendering an image of a 3D object to a texture.

Volumetric Billboards

Volumetric billboards use volumetric images of an object stored into 3D textures, instead of 2D images as for standard billboards.

A rendering approach can visually reconstruct the object, offering parallax effects, reduced popping artefacts, etc.

Video not available in on-line slides

DIRECTED READINGDirected reading concerning billboarding

Directed

reading

Directed reading: Directed

reading

• Read Billboarding Tutorial – for introductory information on how to render cylindrical or spherical billboards.• Read Real-Time Cloud Rendering for

Games – for an exploration of cloud rendering using billboards.• 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.

Directed reading: Directed

reading

• Read Volumetric Billboards – for more information 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 3D object.• Read Dynamic 2D Imposters: A

Simple, Efficient DirectX 9 Implementation – for information on how to implement dynamic imposters at:

http://www.gamasutra.com/view/feature/2501/dynamic_2d_imposters_a_simple_.php

Summary

To do:Read the directed

readingThink if you would like

to implement any aspect of billboarding within your project?

Today we explored:

The variety of uses that billboarding offers within games.