IRAY Rendering invisible objects that cast shadows
anneghostghost
Posts: 12
Hi everyone
I really like the 3delight suggestion of using Ubersurface 2 material options "Fantom" (http://www.daz3d.com/forums/discussion/17295/rendering-invisible-objects-that-cast-shadows). "When Fantom is On, the surface will not be visible to the camera, but will be visible to shadows and raytracing. This can be useful when an object is used to create a reflection or shadow, but we do not want to see the object"
It's very handy for a postwork in photoshop. I need to rendering each object separately and then, edit in layers.
do you know a similar solution for Iray renders? I want to hide an object but want to keep its effect. I really need transparent backgrounds.
thank you
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Please remember that some people use the Dark theme for reading the forums, and half of your post is not readable in the dark theme.
Sort of possible, but it's not simple, and the interface has not at all been documented.
Iray supports the concep of "canvases," which are in effect virtual windows that the renderer draws images on. You can dictate what the canvas shows. Access the canvas feature by clicking on the Advanced tab when in the Iray render panel, then Canvases. Tick off the chedkbiox next to "Canvases" so you can add or remove a canvas. You can render to multiple canvases at once.
The primary canvas is called "Beauty," which is everything combined. There are ways to isolate the objects in the scene so you can render them separately. When I say ways, I mean WAYS -- lots of them. The easier ones may, or may not, be what you want, but you should experiment anyway, because learning the canvas feature is the road to Iray mastery.
1. Click the plus button, and added the Beauty canvas.
2. At the bottom of the pane, click the + besides Nodes. Give your node a name -- the default NL1 is fine.
3. Click the almost-impossible-to-see dot-dot-dot (...) button to the immediate right. A list of scene elements appears.
4. Select the elements you want to render.
5. In the middle of the pane, click the Nodes pulldown, and choose NL1.
6. Now render. Only the selected objects will render. The idea here is to save each render separately, and combine them in a program like Photoshop.
Notes:
A. Renders will not have an alpha transparency background. This is not uncommon for compositing purposes, but if you want the transparency (like I usually do), be sure to enable the Alpha option in the panel.
B. Adding or removing scene lights from the node list does NOT turn those lights on or off. With this technique, if you want to do that, you need to enable/disable the scene lights directly.
So, that's one way. You don't want to know the other ways. Really. Stuff of nightmares...
I can't thank you enough! perfect, this works really good.
Sorry to necro this, but Tobor's steps simply turn objects not in the node list into matte objects. This means they will be invisible in the canvas, but so will anything behind these objects. How can one retain the shadows of an object yet hide the object so that content behind it is still visible? This is a one-click function available in other physically based renderers (Redshift for instance), so I'm pretty sure it's possible with Iray.
Technically, any renderer which supports having an invisible object casting shadows is NOT "physically based" since any invisible object would not be able to cast a shadow. Iray is true PBR, so any object that is invisible cannot cast a shadow.....just like in real life.