Secrets of Swimsuit Babeby Jimmy Chow, Hong Kong
Rendering
Lighitng - FG (Final Gather) with IBL (Image Based Lighting) is my favourite lighting scheme because it is fast and the result looks natural. In this scene, the lighting is indoor because the character is standing on a stage. As the IBL image (see section 6.3 for download URL) is captured in an outdoor environment, a plane is required to block the lights coming from above. Some lights are added to further describe the character. They’re at about the level of the head as shown in the figure below.
The thing to watch is that the position of the chin shadow on the neck should not be too low. It should be well above the collar bones or should terminate half way down the neck at most. Its edge should also be blurry enough. So the mental ray area lights in some spotlights are turned on to produce blurry shadows. They’re indicated by the rectangles attached to the spotlights as shown in above figure. There’s no occlusion on the character because its effect is not significant after combining with shadows. The way how occlusion can be produced will be explained in next section. As shown in above image, there’re two directional lights in front of the eyes. They’re to produce reflections on the eyes. There’re two of them because the eyes are facing at different angles and so their directions are different.
Shading
SSS Fast Skin - In the sss fast skin shader, a ramp (remapValue) is connected to the subdermal channel.
The output of the ramp is driven by surface luminance. The ramp color is tuned so
as to simulate the color transition from day side to night side. This tuning depends
on how you want the skin tone look and can be very different under different
conditions. I tried to apply the skin coloring technique used in painting. Color of
day side is very light. It can be nearly white or light pink. Night side is more
saturated. It may look brownish. The transition between them usually appears
greenish. The resulting sss fast skin and the ramp value shaders are shown in the
following figure:
Since subdermal channel is driven by surface luminance, if occlusion is to be added, it should multiply surface luminance before connected to the ramp as oppose to rendering of other non-sss objects which can be multiplied by a separate occlusion pass.
For this resolution (1500 x 1000) and camera position, there’s no need to have bump in the shader. The irregularity on the skin surface can be imitated by adding some noise to the subdermal channel. This is achieved by adding the output of a Brownian 3D texture to surface luminance before connected to the ramp. The results with and without noise are shown in the following figure:
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