4 . 11. trees and vegetation
DESCRIPTION
4 . 11. Trees and Vegetation. Rendering of trees and vegetation. Vegetation. Rendering flora. Video not available in on-line slides. Grass. Grass is typically rendered using (randomly) placed intersecting quads which are texture mapped and rendered with an alpha test. - PowerPoint PPT PresentationTRANSCRIPT
4.11. TREES AND VEGETATIONRendering of trees and vegetation
VEGETATIONRendering flora
Video not available in on-line slides
Grass
Grass is typically rendered using (randomly) placed intersecting quads which are texture mapped and rendered with an alpha test.
The grass quad are crossed (using a star-like configuration) to ensure good visual quality independent of the line of sight.
GrassDifferent alpha/depth tests can be used at runtime to suitably render a clump of grass quads and provide the appearance of densely packed grass.
Grass
In a vertex shader the top two vertices of each quad can be animated (using a combination of sinusoidal waves) to provide a natural looking wave modelled motion due to wind effects.
By having separate animation parameters for each cluster or clump of grass, more chaotic (i.e. natural) behaviour can be introduced.
GrassWhen lighting the grass, the quad’s normal may also be updated to reflect the grass movement.
Alternatively, the colour change can be simulated by directly modifying the rendered colour based on the oscillations.
TREESRendering trees
Video not available in on-line slides
Trees
At a distance, a tree can be adequately rendered using a billboard or imposter.
Up close, trees are typically separated into two different parts: •solid component of the tree (trunk and branches)•foliage or leaves.
The trunk and the branches are represented using a triangle mesh. Leaves are represented using an image of a leaf group textured using a quad.
Minor branches can be
approximated by simple
polygon strips
Leaves are rendered as
texture mapped quads
More sophisticat
ed tree rendering deals with issues such
as silhouette clipping
Or accurate
leaf shadowing /
lighting
DIRECTED READINGDirected reading regarding trees and vegetation
Directed
reading
Directed reading: Directed
reading
• Read GPU Gems - Rendering Countless Blades of Waving Grass – for coverage of how to render grass• Read Creation and
Rendering of Realistic Trees – for an early paper on generating trees• Read GPU Gems 3 - Next-
Generation SpeedTree Rendering – for an exploration of current tree rendering approaches
Summary
To do:Read the directed
readingThink if you would like
to implement either approach within your project
Today we explored:
Overview of vegetation rendering
Overview of tree rendering