In 3D software, caustics rendering is set based on
luminance values (luminance value must be higher than
0) of the shader applied to a dummy CG object, which
receives caustics from transparent CG objects. The issue
is that if the caustics are received by the dummy CG
surfaces, the luminance value of the CG surfaces must be
0. Because in digital compositing, 0 means completely
transparent, any value above 0 means semi-transparent
and 1 means 100% opaque, thus if the value is 0, the
rendered caustics on dummy CG surfaces can be
composited with live-action footage seamlessly and
without showing any colors from the CG dummy surface
on the footage. However, there is a known issue with
Maya the mental ray engine, which is not fully
compatible with Maya nodes.
Test one: Test one was performed by applying a default
“Surface Shader” (“Surface Shader” uses Maya default
shading algorithms which black the dummy object with a
zero value) to a dummy surfaces, then position the
dummy object behind a transparent character in order to
receive caustics from the transparent CG character, the
result of rendering was a completely black image without
being able to catch any caustics cast on it.
Test two: In test two, a “Background Shader” was
applied to the same dummy surface (Background Shader
is a Maya default shader, it allows catching reflection,
specularity, and shadow without rendering the object
itself). It was assumed that this method would provide an
acceptable result, which only renders the caustics area
and keeps rest of the parts with a value of 0, so it could
be used for compositing purposes. However, the result
was not successful and could see some small values in
the background where supposes to be completely black.
Solution: The solution for rendering an image with
successful caustics was to change the “Color” and
“Weight” attributes of the shader, which was used for
receiving caustic objects. In addition, the value of caustic
phones was also increased to 3000000, photon intensity
was increased to 800000 and the photon exponent value
was reduced to 0.01. The following image Figure 9
Shows a comparison result of rendering caustics.
In 3D software, caustics rendering is set based on
luminance values (luminance value must be higher than
0) of the shader applied to a dummy CG object, which
receives caustics from transparent CG objects. The issue
is that if the caustics are received by the dummy CG
surfaces, the luminance value of the CG surfaces must be
0. Because in digital compositing, 0 means completely
transparent, any value above 0 means semi-transparent
and 1 means 100% opaque, thus if the value is 0, the
rendered caustics on dummy CG surfaces can be
composited with live-action footage seamlessly and
without showing any colors from the CG dummy surface
on the footage. However, there is a known issue with
Maya the mental ray engine, which is not fully
compatible with Maya nodes.
Test one: Test one was performed by applying a default
“Surface Shader” (“Surface Shader” uses Maya default
shading algorithms which black the dummy object with a
zero value) to a dummy surfaces, then position the
dummy object behind a transparent character in order to
receive caustics from the transparent CG character, the
result of rendering was a completely black image without
being able to catch any caustics cast on it.
Test two: In test two, a “Background Shader” was
applied to the same dummy surface (Background Shader
is a Maya default shader, it allows catching reflection,
specularity, and shadow without rendering the object
itself). It was assumed that this method would provide an
acceptable result, which only renders the caustics area
and keeps rest of the parts with a value of 0, so it could
be used for compositing purposes. However, the result
was not successful and could see some small values in
the background where supposes to be completely black.
Solution: The solution for rendering an image with
successful caustics was to change the “Color” and
“Weight” attributes of the shader, which was used for
receiving caustic objects. In addition, the value of caustic
phones was also increased to 3000000, photon intensity
was increased to 800000 and the photon exponent value
was reduced to 0.01. The following image Figure 9
Shows a comparison result of rendering caustics.
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