Techniques that control directly the interaction of shape, materials and lighting;

 


Surface Flows

Last modified on 2013-05-16 15:29:00 GMT. 0 comments. Top.

Approach: It is shown how to produce convincing shadings by relying on image deformations instead of complex simulation of light transport. We first perform a differential analysis of reflected radiance and then use the findings to introduce image operators that approximate surface flows while providing the direct creation of appearance.

Contributions: Our image-based shading design technique is not only less computationally expensive compared to conventional shading, but more importantly offers a direct artistic control in the picture plane. In particular, we introduce two novel deformation operators that closely approximate surface flows while providing direct artistic controls in real-time.

Limitations: The method focuses on deformation patterns founds in textured and shaded 3D objects, but relies on simple blurring to convey material properties. Moreover, it is specialized to the creation of still imagery.

Direct painting of highlights

Publications

Surface Flows for Image-Based Shading Design, Romain Vergne, Pascal Barla, Xavier Granier, Roland Fleming, ACM Transactions on Graphics (Proceedings of Siggraph 2012).

Software

Simple versions of both deformation operators are available as a Pixel Bender shaders.

 


Dynamic Stylized Shading

Last modified on 2013-05-16 15:31:46 GMT. 0 comments. Top.

Approach: Shading primitives, each controlled by a single light source, are used to convey material characteristic, surface features and stylization effects at once. They are based on a simple shading model with a parameters that control color, extent, intensity profile, anisotropy and surface enhancement. A few primitives are sufficient to mimic a variety of shading styles, and parameters are interpolated in real-time to create dynamic rendering effects.

Contributions: Primitives provide a simple means to quickly reproduce a style without having to separately deal with material and illumination. A single model is provided for diffuse and specular effects. Shape enhancement directly modifies the extent of a primitive, which better preserves stylization than Radiance Scaling.

Limitations: A direct painting interface would be more adapted for primitive creation. The method is limited to opaque materials: it does not deal with mirror or transparent objects. It also only works with direct lighting, without explicitly handling visibility.

A stylized metal effect

Publications

Dynamic Stylized Shading Primitives, David Vanderhaeghe, Romain Vergne, Pascal Barla, William Baxter, NPAR’11: Proc. symposium on Non-Photorealisatic Animation and Rendering

Software

The GLSL shader used to render a primitive is given in the appendix of the article.

 


Apparent Relief

Last modified on 2013-05-16 15:45:05 GMT. 0 comments. Top.


Approach:
Object-space surface curvature measurements are combined with image-space normal variations to build a hybrid surface shape descriptor. Specific features are then selected using Koenderink’s shape index, and conveyed through a variety of stylized shading techniques.

Contributions: Our hybrid object- and image-space measurements allow to automatically select relevant details to depict. The shape index is shown to provide an intuitive parameter space for feature selection. The method does not require complex lighting to depict fine details.

Limitations: Our hybrid descriptor requires pre-processing and exhibits artifacts near occluding contours. The method is limited to simple stylized rendering.

Minimal shading style

Publications

Shading with Apparent Relief, Romain Vergne, Pascal Barla, Xavier Granier, Christophe Schlick, SIGGRAPH ‘08: ACM SIGGRAPH 2008 talks – aug 2008
Apparent relief: a shape descriptor for stylized shading, Romain Vergne, Pascal Barla, Xavier Granier, Christophe Schlick, Proceedings of the 6th international symposium on Non-photorealistic animation and rendering, page 23–29 – 2008

Software

The method is provided as a GLSL shading package.

 


X-Toon shading

Last modified on 2013-05-17 09:57:53 GMT. 0 comments. Top.

Approach: The classic 1D texture used for toon shading is extended to a 2D texture, where the additional axis may be used for a host of scene-based variations: depth for aerial perspective, orientation for rim lighting, etc.

Contributions: The method is trivially implemented and simple to use since the 2D toon texture may be directly edited in an image processing software like Photoshop or Gimp. Additional effects are provided by smoothing out normals via a proxy simplified 3D object.

Limitations: Only one effect may be controlled at a time, and each new effect requires an apropriate mapping to the vertical axis of the texture.

landscape_aerial4

Aerial perspective effect

Publications

X-Toon: An extended toon shader, Pascal Barla; Joëlle Thollot; Lee Markosian, International Symposium on Non-Photorealistic Animation and Rendering (NPAR), 2006

Software

The method is currently considered for integration inside Blender.