Transcript Rendering Plant Leaves Faithfully

Rendering Plant Leaves
Faithfully
Oliver Franzke
(Dresden University of Technology)
Oliver Deussen
(University of Konstanz)
Contents
1.
2.
3.
4.
Optical properties of plants
Previous approaches
The new method
Results
Optical properties of
plants
• have been studied for years
• are interesting for:
– computer graphics
– biologists
– architects
–…
• are very important, because we see plants
every day…
Optical properties of
plants
• a leaf consists of several layers
• each layer causes reflection, refraction and
scattering of light
Optical properties of
plants
• a BRDF of a real leaf looks like this:
Previous approaches
• early methods use:
– a stochastic model (Tucker and Garatt)
– a volumetric model (Govaerts et al.)
– a layered model (Baranoski and Rokne)
• each approach tries to be physically correct
– the main problem is the efficiency
– it is difficult to compute complex scenes or
animations
Previous approaches
• Jensen et al. presented a model
to render translucent materials quite fast
• Even highly scattering media can be
represented efficiently
• problems:
– difficult to describe heterogeneous materials
– veins of leaves: substructure information is very
important
The new method
Our goal:
render translucency in plants accurately and
efficiently i.e.
– calculate animations and/or complex scenes
– light source behind the leaf: one should see veins
and other sub-structures
– should be easy to render different types of plants
The new method
• real leaves are source for all required
information
• a set of seven texture maps is necessary to
describe the leaf
• images can be obtained with an ordinary
camera and a scanner
The new method
• adaxial and abaxial textures
The new method
• through-light, thickness and extinction
The new method
• bump and alpha map
The new method
Putting it all together:
• we trace the current view ray as it passes
through the leaf
• there are three layers
– The size of each layer is a fixed percentage of the
current thickness (Thickness map)
• the view ray is refracted at each boundary
• at each step, we have to sample all lights
The new method
The new method
• if the light source is at the same side as the
viewer, then we use the adaxial (or abaxial)
texture map
• otherwise we choose the through-light map
(the selected texture map stores the
reflected color…)
• the intensity of the light decreases
exponentially through passing the leaf
interior
The new method
Optimization/Simplification:
• sample the shadow just once
• approximate the multi-scattered light with an
small ambient term
Results
• the new model is a fast approach
… though it is not physically correct
• rendering time between
– some seconds for small scenes (2 leaves)
– 10 minutes for complex scenes
Results
• A simple plant…
Results
• A collection of different plants…
Results
• A tree…
Results
• Animations…
Future works
• improve rendering of larger plants (trees)
• full support of global illumination
• hardware oriented approximation
That‘s it...
Thank you for your attention!
Are there questions?