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

[Geenz Spad]

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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 27, 2012, 9:54 a.m.)


Review request for Viewer and David Parks.


Changes
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Updated build link.


Description
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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
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  doc/contributions.txt UNKNOWN 
  indra/newview/app_settings/settings.xml UNKNOWN 
  indra/newview/app_settings/shaders/class1/deferred/multiPointLightF.glsl UNKNOWN 
  indra/newview/app_settings/shaders/class1/deferred/pointLightF.glsl UNKNOWN 
  indra/newview/app_settings/shaders/class1/deferred/softenLightF.glsl UNKNOWN 
  indra/newview/app_settings/shaders/class2/deferred/softenLightF.glsl UNKNOWN 
  indra/newview/llviewercontrol.cpp UNKNOWN 
  indra/newview/pipeline.h UNKNOWN 
  indra/newview/pipeline.cpp UNKNOWN 

Diff: http://codereview.secondlife.com/r/565/diff/diff


Testing (updated)
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* 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/latest.html


Thanks,

Geenz Spad

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