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### #Actuallipsryme

Posted 12 July 2013 - 03:45 PM

I've seen quite often that the diffuse term is being modulated by a diffuse fresnel term using NdotL as an approximation like so:

Ldiff = cdiff * (cosTheta_i * E_L * (1.0f - DiffuseFresnel));


What I don't quite understand is since cdiff is already the directional hemispherical reflectance constant of lambert's BRDF should that not already be energy conserving ? Since we only define the diffuse color in between [0-1]. Do We need to do this because we combine it with a specular brdf ? But shouldn't it be enough then to only make sure that the specular term is energy conserving ?

Am I missing something ?

### #3lipsryme

Posted 12 July 2013 - 03:44 PM

I've seen quite often that the diffuse term is being modulated by a diffuse fresnel term using NdotL as an approximation like so:

Ldiff = cdiff * (cosTheta_i * E_L * (1.0f - DiffuseFresnel));


What I don't quite understand is since cdiff is already the directional hemispherical reflectance constant of lambert's BRDF should that not already be energy conserving ? Since we only define the diffuse color in between [0-1]. Do We need to do this because we combine it with a specular brdf ?

Am I missing something ?

### #2lipsryme

Posted 12 July 2013 - 03:44 PM

I've seen quite often that the diffuse term is being modulated by a diffuse fresnel term using NdotL as an approximation like so:

Ldiff = cdiff * (cosTheta_i * E_L * (1.0f - DiffuseFresnel));


What I don't quite understand is since cdiff is already the directional hemispherical reflectance constant of lambert's BRDF should that not already be energy conserving ? Since we only define the diffuse color in between [0-1].

Am I missing something ?

### #1lipsryme

Posted 12 July 2013 - 03:43 PM

I've seen quite often that the diffuse term is being modulated by a diffuse fresnel term using NdotL like so:

Ldiff = cdiff * (cosTheta_i * E_L * (1.0f - DiffuseFresnel));


What I don't quite understand is since cdiff is already the directional hemispherical reflectance constant of lambert's BRDF should that not already be energy conserving ? Since we only define the diffuse color in between [0-1].

Am I missing something ?

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