I use blender to export a OBJ file and mtl file. The content of mtl file: # Blen

Question

I use blender to export a OBJ file and mtl file. The content of mtl file:

# Blender MTL File: 'None'
# Material Count: 2

newmtl board
Ns 96.078431
Ka 1.000000 1.000000 1.000000
Kd 0.640000 0.304212 0.020880
Ks 0.500000 0.500000 0.500000
Ke 0.000000 0.000000 0.000000
Ni 1.000000
d 1.000000
illum 2

newmtl wall
Ns 96.078431
Ka 1.000000 1.000000 1.000000
Kd 5.600001 0.227508 0.492209
Ks 0.500000 0.500000 0.500000
Ke 0.000000 0.000000 0.000000
Ni 1.000000
d 1.000000
illum 2

How can i calculate the rgb of these two objects? I only change the color by changing the diffuse rgb in blender.

Explanation / Answer

Following are the three illumination models and respective formulae for calculating rgb value:

1. Constant color illumination model.

color = Kd

2. Diffuse illumination model using Lambertian shading. There are two terms in this equation,ambient and diffuse shading terms. Second term is for each light source.

color = KaIa + Kd { SUM j=1..ls, (N * Lj)Ij }

3. Diffuse and specular illumination model.  Similar to above formula there are two terms in this equation, ambient and a diffuse and specular shading term. Second term is for each light source. The formula is:

color = KaIa + Kd { SUM j=1..ls, (N*Lj)Ij } + Ks { SUM j=1..ls, ((H*Hj)^Ns)Ij }

where,

L = unit light vector

V = unit view vector

N = unit surface normal

H = unit vector bisector between L and V

Ia = ambient light

Ka = ambient reflectance

Kd = diffuse reflectance

Ks = specular reflectance

Ij = intensity of light j

Since you change the color by changing only diffuse rgb, use formula given in 2 to calculate rgb value.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.