[opensource-dev] Review Request: STORM-1823 - Replace current specular model with Normalized Blinn-Phong specularity

Oz Linden oz at lindenlab.com
Sun Mar 25 11:08:15 PDT 2012



> On March 25, 2012, 2:55 a.m., Tofu Buzzard wrote:
> > I'd like to see the mis-named handleReleaseLUTBufferChanged be called handleLUTBufferChanged, and ideally I'd like some comment (probably in the LUT creation) about why the results of lookups should be multiplied by 4 (to avoid saturation in the LUT?).
> > Otherwise, I reckon this is great.

I concur with both of these comments, and have asked for a review from Dave.


- Oz


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On March 25, 2012, 11:06 a.m., Geenz Spad wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> http://codereview.secondlife.com/r/565/
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> 
> (Updated March 25, 2012, 11:06 a.m.)
> 
> 
> Review request for Viewer and David Parks.
> 
> 
> Description
> -------
> 
> For a while now, Second Life's deferred renderer has had a somewhat "toonish" looking specular model, as opposed to other platforms which try to go for more physically accurate looking models, such as blinn-phong and similar.
> 
> This feature changes the specular model to a technique called normalized blinn-phong. The specular model applies the usual blinn-phong term (assume NdotV to the power of n), multiplied by a normalization function of:
> ((n + 2) * (n + 4)) / (8 * PI * (powf(2, -n/2) + n))
> Where n is the specular exponent.
> 
> Gamma correction is also applied to the result to bring the visual results more in line with what you see in high end game engines such as Unreal Engine 3 and Frostbite 2, and stored in a lookup texture.
> 
> Test plan can be found in the JIRA.
> Repository can be found here: https://bitbucket.org/Geenz/viewer-nbp
> 
> 
> This addresses bug STORM-1823.
>     http://jira.secondlife.com/browse/STORM-1823
> 
> 
> Diffs
> -----
> 
>   doc/contributions.txt b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/app_settings/settings.xml b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/app_settings/shaders/class1/deferred/multiPointLightF.glsl b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/app_settings/shaders/class1/deferred/pointLightF.glsl b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/app_settings/shaders/class1/deferred/softenLightF.glsl b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/app_settings/shaders/class2/deferred/softenLightF.glsl b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/llviewercontrol.cpp b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/pipeline.h b32595c5170f92ac2dbab635955b1b86634f1475 
>   indra/newview/pipeline.cpp b32595c5170f92ac2dbab635955b1b86634f1475 
> 
> Diff: http://codereview.secondlife.com/r/565/diff/diff
> 
> 
> Testing
> -------
> 
> * Tested performance characteristics - both Normalized Blinn-Phong and the previous model seem to have the same performance
> * Checked the perceived "brightness" of the new highlights vs. the old ones - new ones seem much brighter at higher shiny values than the old ones, and seem much less "cartoonish" as such
> * Checked the impact on different bumpiness values at the test rig at Hippo Hollow - noticeable visual improvement across all objects (though low shiny seems to have a much more subtle light reflectance term - this is expected for normalized blinn-phong)
> * Tested different LUT resolutions - best looking seems to be 512x128 with seemingly no measurable decrease in performance
> 
> You can find the latest build here: http://automated-builds-secondlife-com.s3.amazonaws.com/hg/repo/oz_project-8/rev/251711/index.html
> 
> 
> Thanks,
> 
> Geenz Spad
> 
>

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