3 Feb 2012 00:22

### Pick dominant light from sh coeffs

I have 9 red, 9 green and 9 blue sh coefficients (packed using the method in appendix 10 of http://www.ppsloan.org/publications/StupidSH36.pdf).

I want to pick a single dominant light to use for specular. How would I go about efficiently extracting the direction and color of that light from the coefficients?

Looks like I need to calculate the "optimal linear direction" which is supposedly in this paper http://research.microsoft.com/en-us/um/people/johnsny/papers/ldprt.pdf, however I can't see it. Worse still, if it is in there, it is probably an integral that I will struggle to turn into code!

Thanks

Dan

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3 Feb 2012 00:54

### Re: Pick dominant light from sh coeffs

Looks like you want to normalize the 3d vector made from the basis coefficients (-f[1,1], -f[1,-1], f[1,0]). Section 3.3 ZH Error Analysis paragraph 2.

-= Dave

From: Dan Treble [mailto:daniel.treble <at> gmail.com]
Sent: Thursday, February 02, 2012 3:22 PM
To: gdalgorithms-list <at> lists.sourceforge.net
Subject: [Algorithms] Pick dominant light from sh coeffs

I have 9 red, 9 green and 9 blue sh coefficients (packed using the method in appendix 10 of http://www.ppsloan.org/publications/StupidSH36.pdf).

I want to pick a single dominant light to use for specular. How would I go about efficiently extracting the direction and color of that light from the coefficients?

Looks like I need to calculate the "optimal linear direction" which is supposedly in this paper http://research.microsoft.com/en-us/um/people/johnsny/papers/ldprt.pdf, however I can't see it. Worse still, if it is in there, it is probably an integral that I will struggle to turn into code!

Thanks

Dan

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3 Feb 2012 01:21

### Re: Pick dominant light from sh coeffs

This is actually quite straightforward.

The optimal linear direction is -L[3],-L[1],L[3] - assuming the usual sign conventions, storage, etc.

where in your case L could be the luminance of the RGB SH vectors.

If you are using the coefficients from appendix 10, it turns out to be even simpler - it is just the .xyz coefficients after doing a luminance weighting of cAr/cAg/cAb.

That give you the direction.

To generate the color of the light, you can simply evaluate the outgoing radiance using the above direction (as in the shader code in the appendix), and that's the color for the light (if illuminating a white material that is the light in the given direction that would give you the same diffuse response as the SH probe.)

See the section of the paper titled: "Extracting Conventional Lights from SH" on a technique to solve for both a colored directional light and an ambient light given SH coefficients, but if you are using the storage in appendix 10 it's a bit trickier since the DC term has been "polluted" by part of the quadratic ZH function to make evaluation faster. You would have to reconstruct the original vector to do the math...

Peter-Pike Sloan

Date: Fri, 3 Feb 2012 09:22:21 +1000
From: daniel.treble <at> gmail.com
To: gdalgorithms-list <at> lists.sourceforge.net
Subject: [Algorithms] Pick dominant light from sh coeffs

I have 9 red, 9 green and 9 blue sh coefficients (packed using the method in appendix 10 of http://www.ppsloan.org/publications/StupidSH36.pdf).

I want to pick a single dominant light to use for specular. How would I go about efficiently extracting the direction and color of that light from the coefficients?

Looks like I need to calculate the "optimal linear direction" which is supposedly in this paper http://research.microsoft.com/en-us/um/people/johnsny/papers/ldprt.pdf, however I can't see it. Worse still, if it is in there, it is probably an integral that I will struggle to turn into code!

Thanks

Dan

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3 Feb 2012 02:28

### Re: Pick dominant light from sh coeffs

So in layman's terms I am using these three http://imgur.com/oOddh coefficients to derive the direction of the strongest light. Makes sense now.

That is much easier than I expected, thank you for taking the time to explain it.

On Fri, Feb 3, 2012 at 10:21 AM, Peter-Pike Sloan wrote:
This is actually quite straightforward.

The optimal linear direction is -L[3],-L[1],L[3] - assuming the usual sign conventions, storage, etc.

where in your case L could be the luminance of the RGB SH vectors.

If you are using the coefficients from appendix 10, it turns out to be even simpler - it is just the .xyz coefficients after doing a luminance weighting of cAr/cAg/cAb.

That give you the direction.

To generate the color of the light, you can simply evaluate the outgoing radiance using the above direction (as in the shader code in the appendix), and that's the color for the light (if illuminating a white material that is the light in the given direction that would give you the same diffuse response as the SH probe.)

See the section of the paper titled: "Extracting Conventional Lights from SH" on a technique to solve for both a colored directional light and an ambient light given SH coefficients, but if you are using the storage in appendix 10 it's a bit trickier since the DC term has been "polluted" by part of the quadratic ZH function to make evaluation faster. You would have to reconstruct the original vector to do the math...

Peter-Pike Sloan

Date: Fri, 3 Feb 2012 09:22:21 +1000
From: daniel.treble <at> gmail.com

To: gdalgorithms-list <at> lists.sourceforge.net
Subject: [Algorithms] Pick dominant light from sh coeffs

I have 9 red, 9 green and 9 blue sh coefficients (packed using the method in appendix 10 of http://www.ppsloan.org/publications/StupidSH36.pdf).

I want to pick a single dominant light to use for specular. How would I go about efficiently extracting the direction and color of that light from the coefficients?

Looks like I need to calculate the "optimal linear direction" which is supposedly in this paper http://research.microsoft.com/en-us/um/people/johnsny/papers/ldprt.pdf, however I can't see it. Worse still, if it is in there, it is probably an integral that I will struggle to turn into code!

Thanks

Dan

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21 Feb 2012 19:52

### CFP - INTERNATIONAL JOURNAL OF EXPERIMENTAL ALGORITHMS(IJEA)

CALL FOR PAPERS - INTERNATIONAL JOURNAL OF EXPERIMENTAL ALGORITHMS (IJEA)
ISSN:  2180-1282

Volume 3, Issue 1

Computer Science Journals (CSC Journals) invites researchers, editors, scientists & scholars to publish their scientific research papers in an International Journal of Experimental Algorithms (IJEA) Volume 3, Issue 1.

Experimental Algorithmics studies algorithms and data structures by joining experimental studies with the more traditional theoretical analyses. With this regard, the aim of The International Journal of Experimental Algorithms (IJEA) is (1) to stimulate research in algorithms based upon implementation and experimentation; in particular, to encourage testing, evaluation and reuse of complex theoretical algorithms and data structures; and (2) to distribute programs and testbeds throughout the research community and to provide a repository of useful programs and packages to both researchers and practitioners. IJEA is a high-quality, refereed, archival journal devoted to the study of algorithms and data structures through a combination of experimentation and classical analysis and design techniques. IJEA contributions are also in the area of test generation and result assessment as applied to algorithms.

CSC Journals anticipate and invite papers on any of the following topics:

 Algorithm Engineering Dynamic Graph Algorithms Algorithmic Code Experimental Techniques and Statistics Algorithmic Engineering Graph Manipulation Algorithmic Network Analysis Graphics Analysis of Algorithms Heuristics Approximation Techniques Mathematical Programming For Algorithms Cache Oblivious algorithm Metaheuristic Methodologies Combinatorial Optimization Network Design Combinatorial Structures and Graphs Parallel Processing Computational Biology Randomized Techniques in Algorithms Computational Geometry Routing and Scheduling Computational Learning Theory Searching and Sorting Computational Optimization Topological Accuracy Data Structures Visualization Code Distributed and Parallel Algorithms VLSI Design

Important Dates - IJEA CFP - Volume 3, Issue 1.

Paper Submission: March 31, 2012

Issue Publication: June 2012

For complete details about IJEA archives publications, abstracting/indexing, editorial board and other important information, please refer to IJEA homepage.

We look forward to receive your valuable papers. If you have further questions please do not hesitate to contact us at cscpress <at> cscjournals.org. Our team is committed to provide a quick and supportive service throughout the publication process.

A complete list of journals can be found at http://www.cscjournals.org/csc/bysubject.php

Sincerely,

J. Stewart
Computer Science Journals (CSC Journals)

B-5-8 Plaza Mont Kiara, Mont Kiara
50480, Kuala Lumpur, Malaysia

Tel: + 603 6207 1607, + 603 2782 6991
Fax:+ 603 6207 1697
Url: http://www.cscjournals.org

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21 Feb 2012 22:26

### Re: CFP - INTERNATIONAL JOURNAL OF EXPERIMENTAL ALGORITHMS(IJEA)

Oh, look, yet another questionable "academic" for-profit posting on gd-algorithms!

This "international" journal should not be confused with the ACM "Journal of Experimental Algorithms" (which has been going on for a long time.)

That being said -- while the quality of the ACM publication is much higher, the politics and governance of the ACM has gotten so contrary to anything reasonable that I stopped paying my dues...

Sincerely,

jw

--
Americans might object: there is no way we would sacrifice our living standards for the benefit of people in the rest of the world. Nevertheless, whether we get there willingly or not, we shall soon have lower consumption rates, because our present rates are unsustainable.

On Tue, Feb 21, 2012 at 10:52 AM, J. Stewart wrote:

CALL FOR PAPERS - INTERNATIONAL JOURNAL OF EXPERIMENTAL ALGORITHMS (IJEA)
ISSN:  2180-1282

Volume 3, Issue 1

Computer Science Journals (CSC Journals) invites researchers, editors, scientists & scholars to publish their scientific research papers in an International Journal of Experimental Algorithms (IJEA) Volume 3, Issue 1.

Experimental Algorithmics studies algorithms and data structures by joining experimental studies with the more traditional theoretical analyses. With this regard, the aim of The International Journal of Experimental Algorithms (IJEA) is (1) to stimulate research in algorithms based upon implementation and experimentation; in particular, to encourage testing, evaluation and reuse of complex theoretical algorithms and data structures; and (2) to distribute programs and testbeds throughout the research community and to provide a repository of useful programs and packages to both researchers and practitioners. IJEA is a high-quality, refereed, archival journal devoted to the study of algorithms and data structures through a combination of experimentation and classical analysis and design techniques. IJEA contributions are also in the area of test generation and result assessment as applied to algorithms.

CSC Journals anticipate and invite papers on any of the following topics:

 Algorithm Engineering Dynamic Graph Algorithms Algorithmic Code Experimental Techniques and Statistics Algorithmic Engineering Graph Manipulation Algorithmic Network Analysis Graphics Analysis of Algorithms Heuristics Approximation Techniques Mathematical Programming For Algorithms Cache Oblivious algorithm Metaheuristic Methodologies Combinatorial Optimization Network Design Combinatorial Structures and Graphs Parallel Processing Computational Biology Randomized Techniques in Algorithms Computational Geometry Routing and Scheduling Computational Learning Theory Searching and Sorting Computational Optimization Topological Accuracy Data Structures Visualization Code Distributed and Parallel Algorithms VLSI Design

Important Dates - IJEA CFP - Volume 3, Issue 1.

Paper Submission: March 31, 2012

Issue Publication: June 2012

For complete details about IJEA archives publications, abstracting/indexing, editorial board and other important information, please refer to IJEA homepage.

We look forward to receive your valuable papers. If you have further questions please do not hesitate to contact us at cscpress <at> cscjournals.org. Our team is committed to provide a quick and supportive service throughout the publication process.

A complete list of journals can be found at http://www.cscjournals.org/csc/bysubject.php

Sincerely,

J. Stewart
Computer Science Journals (CSC Journals)

B-5-8 Plaza Mont Kiara, Mont Kiara
50480, Kuala Lumpur, Malaysia

Tel: + 603 6207 1607, + 603 2782 6991
Fax:+ 603 6207 1697
Url: http://www.cscjournals.org

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29 Feb 2012 21:38

### CFP - INTERNATIONAL JOURNAL OF ARTIFICIAL INTELLIGENCE AND EXPERT SYSTEMS (IJAE)

CALL FOR PAPERS - INTERNATIONAL JOURNAL OF ARTIFICIAL INTELLIGENCE AND EXPERT SYSTEMS (IJAE)

ISSN: 2180-124X

Volume 3, Issue 3

Computer Science Journals (CSC Journals) invites researchers, editors, scientists & scholars to publish their scientific research papers in an International Journal of Artificial Intelligence and Expert Systems (IJAE) Volume 3, Issue 3.

The main aim of the International Journal of Artificial Intelligence and Expert Systems (IJAE) is to provide a platform to AI & Expert Systems (ES) scientists and professionals to share their research and report new advances in the field of AI and ES. IJAE is a refereed journal producing well-written original research articles and studies, high quality papers as well as state-of-the-art surveys related to AI and ES. By establishing an effective channel of communication between theoretical researchers and practitioners, IJAE provides necessary support to practitioners in the design and development of intelligent and expert systems, and the difficulties faced by the practitioners in using the theoretical results provide feedback to the theoreticians to revalidate their models. IJAE thus meets the demand of both theoretical and applied researchers in artificial intelligence, soft computing and expert systems.

IJAE is a broad journal covering all branches of Artificial Intelligence and Expert Systems and its application in the topics including but not limited to technology & computing, fuzzy logic, expert systems, neural networks, reasoning and evolution, automatic control, mechatronics, robotics, web intelligence applications, heuristic and AI planning strategies and tools, computational theories of learning, intelligent system architectures.

CSC Journals anticipate and invite papers on any of the following topics:

 AI for Service Engineering Integrated/Hybrid AI Approaches AI for Web Intelligence Applications Intelligent Planning AI in Bioinformatics Intelligent Search AI Parallel Processing Tools Intelligent System Architectures AI Tools for CAD and VLSI Analysis/Design/Testing Knowledge Acquisition AI Tools for Computer Vision and Speech Understand Knowledge-Based Systems AI Tools for Multimedia Knowledge-Based/Expert Systems Application in VLSI Algorithms and Mobile Communication Logic Programming Automated Reasoning Machine learning Case-based reasoning Multi-agent Systems Data and Web Mining Neural Computing Derivative-free Optimization Algorithms Neural Networks for AI Emotional Intelligence Object-Oriented Programming for AI Evolutionary and Swarm Algorithms Parallel and Distributed Realization of Intelligence Expert System Development Stages Problem solving Methods Expert Systems Components Reasoning and Evolution of Knowledge Bases Expert-System Development Lifecycle Rough Sets Fuzzy Sets and logic Rule-Based Systems Heuristic and AI Planning Strategies and Tools Self-Healing and Autonomous Systems Hybridization of Intelligent Models/algorithms Uncertainty Image Understanding Visual/linguistic Perception Inference

Important Dates - IJAE CFP - Volume 3, Issue 3.

Paper Submission: March 31, 2012

Issue Publication: June 2012

For complete details about IJAE archives publications, abstracting/indexing, editorial board and other important information, please refer to IJAE homepage.

We look forward to receive your valuable papers. If you have further questions please do not hesitate to contact us at cscpress <at> cscjournals.org. Our team is committed to provide a quick and supportive service throughout the publication process.

A complete list of journals can be found at http://www.cscjournals.org/csc/bysubject.php

Sincerely,

J. Stewart
Computer Science Journals (CSC Journals)

B-5-8 Plaza Mont Kiara, Mont Kiara
50480, Kuala Lumpur, Malaysia

Tel: + 603 6207 1607, + 603 2782 6991
Fax:+ 603 6207 1697
Url: http://www.cscjournals.org
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