Intro

In this assignment you will implement the Ward Anisotropic BRDF$.$

The Ward model uses a $2$D Gaussian function to map the angle H makes with the surface directions u and v$,$ to the fraction of light reflected from the surface$$for a given viewing and lighting angle to the surface normal N$.$

The Ward BRDF computes the following using the unit$-$length N$,$ L$,$ V$,$ H$,$ u$,$ and v vectors:

cos $\backslash$theta i $-$ cosine of the angle between N and L$.$

cos $\backslash$theta r $-$ cosine of the angle between N and V$.$

cos $\backslash$theta n $-$ cosine of the angle between N and H$.$

cos $\backslash$theta u $-$ cosine of the angle between H and u$.$

cos $\backslash$theta v $-$ cosine of the angle between H and v$.$

And uses the following parameters:

u$\_$roughness $-$ roughness in the u surface direction.

v$\_$roughness $-$ roughness in the v surface direction.

The Ward BRDF looks like the following two renders. The left rendering has u$\_$roughness $=0\mathrm{.}25$ and v$\_$roughness $=1\mathrm{.}0.$ The rendering on the right has u$\_$roughness $=1\mathrm{.}0$ and v$\_$roughness $=0\mathrm{.}25.$ The specular color was set to $[011].$

Specifications

I will provide a rib for your scene setup. Your shader should support the following parameters:

Roughness in the u surface direction

Roughness in the v surface direction

Specular color

You should also follow the organization provided in earlier surface lighting shaders, and implement your BRDFs in separate functions called from the illuminance loop.

I will demonstrate the final shader working in an accompanying video. In that video, I provide a walk$-$thru of its parameter usage with sample renders.

Deliverables

You need to submit:

Three $640$ by $480$ jpg files $($no alpha channel$)$ of your final images.

Show default settings $($where u and v roughness are equal and specular color is $[111]).$

Show the highlight with more roughness in the u direction than v$.$

Show the highlight with more roughness in the v direction than u$.$

The shader source file for your implementation.