Sky Browser: Search for HDR Sky Maps


Abstract

In a visual effects studio for movie production, sky maps play an important role for acting as a sky backdrop to a scene. The backdrop to a scene is often represented using a high-resolution sky map. This motivates the need for a large collection of sky maps to match various moods and lighting conditions. A comprehensive collection of images is not useful however, without a method of searching for desired images within that database. In this paper we define a feature space that supports an interactive search function for HDR sky maps, allowing users to find ideal images based on its appearance. The set of features are automatically extracted from the sky maps in an offline pre-processing step, and are queried in real time for progressive browsing. The system uses unsupervised learning techniques, discarding the need for labelling a large set of existing sky maps.


Paper

Andrew Chalmers, John Lewis, Peter Hillman, Charlie Tait and Taehyun Rhee
Sky Browser: Search for HDR Sky Maps
Pacific Graphics 2014
Author Preprint





Perceptually Optimised Illumination for Seamless Composites


Composition with a photograph: the synthetic objects (blue ball, green block, bunny, and teapot) are illuminated by a radiance map (RM). From left: photograph, rendering with 5024x2512 HDR RM, and two examples of rendering with 320x160 LDR RM having expanded dynamic range using inverse tone mapping. The 2nd and 3rd images are visually equivalent, despite the large difference in RM resolution and dynamic range.

Abstract

Realistic illumination in composition is important for a seamless mixture between the virtual and real world objects in visual effects and mixed reality. The seamlessness is the measure of how perceivably apparent the synthetic object in the final composition is, and how indistinguishable it is from the photographed scene. Given that the ultimate receiver of image information is the human eye, the metric is determined by the Human Visual System (HVS). We conducted a series of psychophysical studies to observe and capture the thresholds of the HVS's ability to perceive illumination inconsistencies between the rendered subject and the photographed scene. Based on our observations, we find perceptually optimised thresholds for reducing resources across resolution and dynamic range of the radiance map (RM) for image based lighting (IBL). We evaluated our thresholds to illuminate virtual objects for seamless composition with photographed scenes.


Paper

Andrew Chalmers, Jong Jin Choi and Taehyun Rhee
Perceptually Optimised Illumination for Seamless Composites
Pacific Graphics 2014
Author Preprint





A Pose Space for Squash and Stretch Deformation


Authors

Richard Roberts
Byron Mallett

Abstract

'Squash & Stretch' is a fundamental technique in traditional animation, in which the shape of a character or object is intentionally distorted in order to accentuate its movement. Unfortunately the fluid deformation required by the squash & stretch technique is difficult to achieve using current tools, because the development of computer graphics algorithms has been largely driven by the goal of producing photo-realistic images and movement. We contribute a novel technique in which the squash & stretch effect can be introduced and controlled simply by specifying examples of the desired effect at any point along an animation timeline. The examples are associated with the pose of the model, where 'pose' is defined as selected parameters of the underlying animation such as position, velocity, and acceleration. Unlike keyframe animation, which would require a squash or stretch to be specified every time that it occurs, our approach automatically produces the desired effect whenever the pose of the model approaches one of the trained poses. And unlike rigging-based approaches, which require the artist to specify various weight and expressions, our approach allows the desired deformations to be produced simply by sculpting them.


Paper

Richard Roberts and Byron Mallett
A Pose Space for Squash and Stretch Deformation
2013 28th International Conference of Image and Vision Computing New Zealand
Author Preprint
Supplementary Video

Example



Further Information

The primary author's overview of the work is featured here.


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