(File of this head is from ICT's website)
I have implemented this method by using Lighting/Shading → Batch Bake from Mental Ray for Maya to bake light maps of each frame. And I wrote script to produce Gauss Blur maps of each light maps of each frame. Then for each frame, I wrote a mental ray node to combine
those maps with the magic values from Skin Diffusion method of GPU Gems 3. But the performance of this way is very poor. Because if any parameter of light has changed, it is need to
bake those light maps again, and will waste time.
So I started to find another way to implement this method and more efficiency. After I referred the sample code of light map of Mental Ray for Maya, I had wrote a light map node for Mantal Ray for Maya. Through this way, it could produse the light map and those Gauss Blur maps and then combine these maps with the magic value automatically while rendering.
I downloaded the face data from ICT's website. This file is provided for Hybrid Normal Map method, so it provide R-channel, G-channel and B-channel normal maps. But I had used only the G-channel normal map for this blog.
The specular of each pictures below is also using the method from the chap.14 of GPU Gems 3.
Just using the G-channel normal map as this face's normal. The shadow is sharp.
Using the Skin Diffusion method of chap.14 of GPU Gems 3. It is more redness of the skin and the shadow is more soft.
If it just render the diffuse part with white color and without using color texure, White Diffuse 2 is more redness of the skin than White Diffure 1.
(White Diffure 1)
(White Diffure 2)
Now, I start to describe what I have done step by step.
Step1. I wrote a mental ray node and used Lighting/Shading → Batch Bake to bake a stretch map. (Please refer the Figure 14-21 of GPU Gems 3)
Step2. Using my light map node to produee the light map and using this light map to make other Gauss Blur maps.
The operation of my light map node is like mib_lightmap_write of Mental Ray for Maya. But beside bake the light map(Texture), I used this light map and the stretch map(Sretch Map) to produce those Gauss Blur maps(Texture 2 ~ 6). Here the Stch Scale is a weight of the stretch map and Input is Diffuse with white color. Note: It is need to use 6 maps and those maps will be wrote by one light map and five Gauss Blur maps. But it will be combined with those magic values to render final image, so, initially, these maps can not be used with workless data.
Step3. Step2 will produce one light map and five Gauss Blur maps.
Step4. I had written a mental ray node to combine these maps with the magic value in Chap.14 of GPU Gems 3.
The final network of shading nodes will have the form below.
Assigning this network to that face and rendering, it will produce the image like the below.
