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Thread: Transparent/Masked Ground Plane

  1. #1
    Pods Guest

    Default Transparent/Masked Ground Plane

    I am using image based lighting and I am able to render a transparent background using a png which is great, but my HDRi is casting a green hue onto my object. I am coming from Blender Cycles where I would just create a ground plane then mask the layer which would make it invisible in the final image but it would still block the bottom of the HDRi and therefore block the green on the object.

    So I guess my question would be - is there a way to mask a ground plane which would show up as transparent in the render but still block light to the object?

  2. #2
    rossh Guest


    Iray is a physically based renderer, which means that there are limitations as to what you can represent in a render. It is a simulation of reality. A surface that is invisible, or in other words transparent, lets light through by definition. An object that appears transparent to your eye but somehow blocks light to an arbitrary object(s) in the same scene is a physical impossibility.

    There is a couple of exceptions to this. If you look in the Iray section of an objects properties, there are settings for Visible and Matte.

    Matte will make the object 'invisible' so the IBL renders through, but will catch reflections and shadows (depending on the material you assign to it). This is good for masking objects in the scene behind objects in the IBL background, or making objects look like they are sitting on top of the background.

    What you should look at is the Visible option. This turns off primary visibility but the object still exists in the scene and will block light. It doesn't render with alpha so this should be exactly what you are after. Just be aware if it is placed too close to your scene objects, it will cast shadows on them too. You'll need to tweak the position, and maybe material on it to be as non-reflective as possible.

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