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Converting Specular from Phong to PBR

Before Lotta/VStitcher 2019 April Edition, the applications used Phong Shader. 2019 April Edition replaces this with Physically Based Rendering (PBR).

The following table summarizes how, using Phong shader and PBR, specular effects are represented.

Specular Effect Parameters
Phong ShaderPBR
  • Specular map

  • Specular color

  • Specular spread

  • Specular map

  • Specular intensity

  • Specular tint

  • Roughness map

  • Roughness intensity

  • Diffuse color

Note: when specular tint has a value, it inherits its color from the diffuse color.


The following table shows in outline how each of the PBR parameters for specular derive their value.

PBRValue Derived From Phong Shader

Specular map

Specular map

Specular intensity

Formula applied to specular color values

Specular tint

  • If specular color is gray scaled:
    • Specular tint = 1
    • Specular intensity is multiplied by the red value of the specular RGB color - multiplication is done before applying the formula for specular intensity
  • If specular color is not gray scaled:
    • Specular tint = 1

Roughness map

Roughness map

Roughness intensity

Formula applied to specular spread value, provided that value is not equal to zero. If specular spread is equal to zero, roughness intensity is set to zero.

Diffuse color

Diffuse color

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