Abstract
Implementation of shadows is crucial to enhancement of images in AR environments. Without shadows, virtual objects would look floating over the scene resulting in unrealistic rendering of AR environments. Casting hard shadows would provide only spatial information while soft shadows help improve realism of AR environments. Several algorithms have been proposed to render realistic shadows which often incurred high computational costs. Little attention has been directed towards the balanced trade-off between shadow quality and computational costs. In this study, two approaches are proposed: Quadratic Spline Interpolation (QSI) to soften the outline of the shadow and Detail Multi-Layer (DML) technique to optimize the volume of computations for the generation of soft shadows based on real light sources. QSI estimates boarder hard shadow samples while DML involves three main phases: real light sources estimation, soft shadow production and reduction of the complexity of 3-Dimensional objects’ shadows. To be more precise, a reflective hemisphere is used to capture real light and to create an environment map. The Median Cut algorithm is implemented to locate the direction of real light sources on the environment map. Subsequently, the original hard shadows are retrieved and a sample of multilayer hard shadows is produced where each layer has its unique size and colour. These layers overlap to produce soft shadows based on the real light sources’ directions. Finally, the Level of Details (LOD) algorithm is implemented to increase the efficiency of soft shadows by decreasing the complexity of vertex transformations. The proposed technique is tested using three samples of multilayer hard shadows with varying numbers of light sources generated from the Median Cut algorithm. The experimental results show that the proposed technique successfully produces realistic soft shadows at low computational costs.
Similar content being viewed by others
References
Agusanto K, Li L, Chuangui Z, Sing N (2003) Photorealistic rendering for augmented reality using environment illumination. In: Proceedings of the 2nd IEEE and ACM international symposium on mixed and augmented reality, pp 208–216
Aittala M (2010) Inverse lighting and photorealistic rendering for augmented reality. Vis Comput 26(6–8):669–678
Annen T, Dong Z, Mertens T, Bekaert P, Seidel HP Kautz J, (2008) Real-time, all-frequency shadows in dynamic scenes. In: ACM transactions on graphics (TOG), vol 27, no 3. ACM, p 34
Azuma R (1997) A survey of augmented reality. Presence: Teleoperators and Virtual Environments 6:355–385
Carmigniani J et al (2011) Augmented reality technologies, systems and applications. Multim Tools Appl 51(1):341–377
Castro T, Figueiredo L, Velho L (2012) Realistic shadows for mobile augmented reality. In: Virtual and augmented reality (SVR). 2012 14th symposium, pp 36–45
Debevec P (2005) A median cut algorithm for light probe sampling. In: International conference on computer graphics and interactive techniques, Los Angeles, California
Dimitrov R (2007) Cascaded shadow maps. Developer documentation, NVIDIA Corp
Gibson S, Murta A (2000) Interactive rendering with real world illumination. In: Proceedings of eurographics symposium on rendering 2000, pp 365–376
Gibson S, Cook J, Howard T, Hubbold R (2003) Rapid shadow generation in real-world lighting environments. In: Proceedings of eurographics symposium on rendering 2003, pp 219–229
Haller M (2004) Photorealism or/and non-photorealism in augmented reality. In: Proceedings of the 2004 ACM SIGGRAPH international conference on virtual, reality continuum and its applications in industry. ACM, pp 189–196
Haller M, Drab S, Hartmann W (2003) A real-time shadow approach for an augmented reality application using shadow volumes. In: Proceedings of VRST 03, pp 56–65
Hartmann W, Zauner J, Haller M, Luckeneder T, Woess W (2003) Shadow catcher: a vision based illumination condition sensor using ARtoolkit. In: 2003 IEEE internation augmented reality toolkit workshop (IEEE Cat. No.03EX780), pp 44–55
Hasenfratz J, Lapierre M, Holzschuch N, Sillion F (2003) A survey of real-time soft shadows algorithms. Eurographics 22(4):753–774
Hensley J, Scheuermann T, Coombe G, Singh M, Lastra A (2005) Fast summed-area table generation and its applications. Comput Graph Forum 24(3):547–555
Herf M, Heckbert PS (1996) Fast soft shadows. In: Visual proceedings SIGGRAPH 96, p 145
Hu B, Brown C (2005) Cast shadows in augmented reality systems. PhD thesis, University of Rochester, Department of Computer Science
Hughes CE, Konttinen J, Pattanaik SN (2004) The future of mixed reality: Issues in illumination and shadows. In: The interservice/industry training, simulation and education conference (I/ITSEC), vol 2004, no 1. National Training Systems Association
Jacobs K, Angus C, Loscos C (2005) Automatic generation of consistent shadows for augmented reality. In: Proceedings graphics interface, Vancouver, Canada
Jensen BF, Laursen JS, Madsen JB, Pedersen TW (2009) Simplifying real time light source tracking and credible shadow generation for augmented reality. Institute for Media Technology, Aalborg University
Kanbara M, Yokoya N (2002) Geometric and photometric registration for real-time augmented reality. In: IEEE and ACM international symposium on mixed and augmented reality (ISMAR), p 279
Kanbara M, Yokoya N (2004) Real-time estimation of light source environment for photorealistic augmented reality. In: Proceedings of the 17th international conference on pattern recognition. Cambridge, UK, pp 911–914
Kolivand H, Sunar SM (2012) An overview on based real-time shadow techniques in virtual environment. Telkomnika 10(1):171–178
Kolivand H, Sunar MS (2013) Covering photo-realistic properties of outdoor components with the effects of sky color in mixed reality. Multimed Tools Appl. doi:10.1007/s11042-013-1494-9
Kolivand H, Sunar SM (2013) A survey on volume shadows in computer graphics. IETE Tech Rev 30(1):38–46
Kolivand H, Sunar MS (2012) Real-time outdoor rendering using hybrid shadow maps. Int J Innov Comput Appl Inf Control (IJICIC) 8(10):7169–7184
Kolivand H, Amirshakarami A, Sunar MS (2011) Real-time projection shadow with respect to sun’s position in virtual environments. Int J Comput Sci Issues 8(6):80–84
Krevelen D, Poelman R (2010) A survey of augmented reality technologies, applications and limitations. Int J Virtual Reality 9(2):1–20
Lensing P, Broll W (2012) Instant indirect illumination for dynamic mixed reality scenes. In: Mixed and augmented reality (ISMAR). 2012 IEEE international symposium, pp 109–118
Madsen CB, Laursen R (2007) A scalable GPU-based approach to shading and shadowing for photo-realistic real-time augmented reality. In: Proceedings international conference on graphics theory and applications. Barcelona, Spain, pp 252–261
Madsen CB, Nielsen M (2008) Towards probe-less augmented reality. A position paper, Computer Vision and Media Technology Lab, Aalborg University, Aalborg, Denmark
Madsen CB, Sorensen MKD, Vittrup M (2003) The important of shadows in augmented reality. In: Proceedings 6th annual international workshop on presence, Aalborg, Denmark
Naemura T, Nitta T, Mimura A, Harashima H (2002) Virtual shadows in mixed reality environment using flashlight-like devices. Trans Virtual Reality Society of Japan 7(2):227–237
Nakano G, Kitahara I, Ohta Y (2008) Generating perceptually-correct shadows for mixed reality. In: 7th IEEE/ACM international symposium on mixed and augmented reality, pp 173–174
Poupyrev I, Tan DS, Billinghurst M, Kato H, Regenbrecht H, Tetsutani N (2002) Developing a generic augmented-reality interface. Computer 35(3):44–50
Sato I, Sato Y, Ikeuchi K (1999) Acquiring a radiance distribution to superimpose virtual objects onto a real scene. IEEE Trans Vis Comput Graph 5(1):1–12
Sood R (2012) A 3D augmented reality model viewer. In: Pro android augmented reality, pp 159–220
Sugano N, Kato H, Tachibana K (2003) The effects of shadow representation of virtual objects in augmented reality. In: IEEE/ACM international symposium on mixed and augmented reality (ISMAR 2003). IEEE Computer Society, pp 76–83
Yan F (2008) Estimation of light source environment for illumination consistency of augmented reality. In: First international congress on image and signal processing, pp 771–775
Yeoh RC, Zhou SZ (2009) Consistent real-time lighting for virtual objects in augmented reality. In: 8th IEEE international symposium on mixed and augmented reality (ISMAR 2009), Orlando, USA, pp 223–224
Acknowledgements
This research was supported by Vot. J13000.7282.4F085 FRGS grant at the UTM VicubeLab, Department of Computer Graphics and Multimedia, Faculty of Computing, Universiti Teknologi Malaysia.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Kolivand, H., Noh, Z. & Sunar, M.S. A quadratic spline approximation using detail multi-layer for soft shadow generation in augmented reality. Multimed Tools Appl 73, 1225–1245 (2014). https://doi.org/10.1007/s11042-013-1630-6
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11042-013-1630-6