Rendering Plant Leaves Faithfully Oliver Franzke (Dresden University of Technology) Oliver Deussen (University of Konstanz)

Rendering Plant Leaves Faithfully

Rendering Plant Leaves Faithfully

Oliver Franzke (Dresden University of Technology)

Oliver Deussen (University of Konstanz)

ContentsContents

1.1. Optical properties of plantsOptical properties of plants

2.2. Previous approachesPrevious approaches

3.3. The new methodThe new method

4.4. ResultsResults

Optical properties of Optical properties of plantsplantsOptical properties of Optical properties of plantsplants

• have been studied for years

• are interesting for:

– computer graphics

– biologists

– architects

– …

• are very important, because we see plants every day…

• have been studied for years

• are interesting for:

– computer graphics

– biologists

– architects

– …

• are very important, because we see plants every day…


• a leaf consists of several layers

• each layer causes reflection, refraction and scattering of light

• a leaf consists of several layers

• each layer causes reflection, refraction and scattering of light


• a BRDF of a real leaf looks like this:• a BRDF of a real leaf looks like this:

Previous approachesPrevious 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

• 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 approachesPrevious 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

• 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 methodThe new methodThe new methodThe 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

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


• 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

• 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


• adaxial and abaxial textures• adaxial and abaxial textures


• through-light, thickness and extinction• through-light, thickness and extinction


• bump and alpha map• bump and alpha map


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

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



• 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

• 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


Optimization/Simplification:

• sample the shadow just once

• approximate the multi-scattered light with an small ambient term

Optimization/Simplification:

• sample the shadow just once

• approximate the multi-scattered light with an small ambient term

ResultsResultsResultsResults

• 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

• 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


• A simple plant…• A simple plant…


• A collection of different plants…• A collection of different plants…


• A tree…• A tree…


• Animations…• Animations…

Future worksFuture works

• improve rendering of larger plants (trees)

• full support of global illumination

• hardware oriented approximation

• improve rendering of larger plants (trees)

• full support of global illumination

• hardware oriented approximation

That‘s it...That‘s it...

Thank you for your attention!Are there questions?

Documents

Rendering Plant Leaves Faithfully Oliver Franzke (Dresden University of Technology) Oliver Deussen (University of Konstanz)