[SOLVED] Canvases and shadow cache (not catch, not cast)

mmdestiny

Morning folks,

I'm already 95% sure this isn't possible, but figured it's worth a shot to ask.  I'm already familiar with using canvases to omit objects from the render, but render as if they were still there reflecting light, casting shadows, etc.  This however only acts as a mask, saving you a step in post.  If the object you're masking out with the canvas covers the whole screen, for example, you get nothing in your render.

What I'm trying to do is something I recall being able to do (though it's been a very long time) in C4D utilizing its cache and bake abilities.

I have an interior scene that I am very happy with the lighting (lit both from the exterior via HDRI through the windows and interior light sources) and all that.  I've got a camera angle I want to shoot, but the ceiling is in the way.  Hiding the ceiling will obviously change how the HDRI lights the scene, moving the camera in through the ceiling changes the composition too much.

Is there any way to render as if the ceiling was still blocking the light from the HDRI, but see through it to the scene?  Like I said, canvases won't work because excluding the ceiling from the canvas just means you get an all black render (everything is "masked").

Richard Haseltine

Yes, add a Section Plane (Create>New Iray Section Plane) and place it below the ceiling, but above everything you do want to see. In the Parameters pane turn on Clip Lights and it will do exactly what you ask.

mmdestiny

Richard Haseltine said:

Yes, add a Section Plane (Create>New Iray Section Plane) and place it below the ceiling, but above everything you do want to see. In the Parameters pane turn on Clip Lights and it will do exactly what you ask.

Brilliant, Richard, thank you!  This is a wonderful tool I was not aware of (as seems to be the case...a lot with this software).