During the render process, you usually want your objects to appear in the final image and affect the lighting of the other objects around. In some cases however you might want to control the objects visibility without changing its material settings, or hide it to the camera but still have it affect the scene - which is a very useful thing especially for emitter geometry. The following object properties are found in the Attributes Panel: Object in Maxwell Studio. For the plugins, please consult their documentation.
Opacity
This object parameter lets you control the objects overall opacity, with a 0-100% range. It can be very useful for illustrative renders - for example to show individual gears inside a watch, while still showing a hint of the cover. If you are using a plugin, this value can also be animated to create interesting reveal animations.
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An interesting use of this option is to make invisible emitters, but maintaining the light they cast in the scene.
The emitter at the top of the box is hidden to the camera
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This option prevents the object from appearing in the reflections of other objects, or from being seen through transparent, refractive objects.
This object (left) is visible in the reflective object and through the transparent object. Right image shows how the object is invisible in the cylinders reflection and also when seen through the glass plane.
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With this option turned on, the object will not affect the global illumination in the scene - it will not cast a shadow or affect color bleeding in the scene.
Enabling this option (right) you can force an object not to cast shadows nor affect other objects with its color bleeding
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