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

Contents 1.Optical properties of plants 2.Previous approaches 3.The new method 4.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… 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 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 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 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 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 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 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

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

The new method 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

ResultsResults 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

ResultsResults A simple plant…

ResultsResults A collection of different plants…

ResultsResults A tree…

ResultsResults Animations…

Future 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... Thank you for your attention! Are there questions?