Archiv des Autors: christian

ShaderX is searched by EPO

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While googling the net, I found this remark­able piece. This is a patent appli­ca­tion from 2010, and from the draw­ings, it seems that the inven­tor had the ‘rev­o­lu­tion­ary’ idea of cal­cu­lat­ing some adap­tive depth bias based on the depth map to improve shad­ow mapping.

The note­wor­thy part of the sto­ry is, that the offi­cial research, the patent clerk appar­ent­ly turned up my ShaderX4 arti­cle from 2006, as can be seen here fur­ther down on the page. The page also states that the appli­ca­tion has been aban­doned. So, maybe the exis­tence of this arti­cle has pre­vent­ed a patent on shad­ow maps, or at least dis­cour­aged the issuer to pur­sue the appli­ca­tion. In either case, let’s hope it stays that way!

We can draw two con­clu­sions from this.

  • Con­clu­sion 1: ShaderX seems to be rec­og­nized by the EPO as a source of state of the art.
  • Con­clu­sion 2: If you have an idea, write about and pub­lish it! It does­n’t mat­ter if it is just a blog post. If it can be tracked down, this can pre­vent a patent on the same idea in the future!

Comments on Advances in Real Time Rendering 2011

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I final­ly got around to write some com­ments on this years Advances in Real Time Ren­der­ing held at SIGGRAPH 2011. Thanks to the RTR-team for mak­ing the notes avail­able. The talk about phys­i­cal­ly-based shad­ing in Call Of Duty has already been men­tioned in my pre­vi­ous post. So, in no par­tic­u­lar order:

Rendering in Cars 2

Christopher Hall, Robert Hall, David Edwards (AVALANCHE Software)

At one point, the talk about ren­der­ing in Cars 2 describes how they use pre-exposed col­ors as shad­er inputs to avoid pre­ci­sion issues when doing the expo­sure after the image has been ren­dered. I have employed pre-exposed col­ors with dynam­ic expo­sure in the past, and I found them tricky to use. Since there is a delay in the expo­sure feed­back (you must know the expo­sure of the pre­vi­ous frame to feed the col­ors for the next frame) you can even get expo­sure oscillation!
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The Blinn-Phong Normalization Zoo

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It is good to see how phys­i­cal­ly based shad­ing is final­ly gain­ing momen­tum in real time graph­ics and games. This is some­thing I have been advo­cat­ing for a long time. Devel­op­ers are spread­ing the word. I was espe­cial­ly sur­prised to learn about Call of Duty: Black Ops join­ing the club [1]. Even a slick 60 Hz shoot­er with no cycles to spare can afford to do PBS today!

This leads me to the top­ic of this post, the nor­mal­iza­tion of the Blinn-Phong spec­u­lar high­light. Why am I writ­ing about it? It came to my mind recent­ly with the cur­rent batch of pub­li­ca­tions from peo­ple adopt­ing phys­i­cal­ly based shad­ing mod­els. This got me check­ing the maths again and I com­piled a list with nor­mal­iza­tion fac­tors for dif­fer­ent shad­ing mod­els, giv­en here in this post. I would also like to elab­o­rate a lit­tle on the mod­el that I wrote about in ShaderX7 [2]. Be aware this post is a large brain dump.
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