Author Topic: Hide Geometry from camera?  (Read 12994 times)

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Offline JBird

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Hide Geometry from camera?
« on: June 13, 2016, 09:08:40 am »
Hi, not new to rendering but new to keyshot. Can someone explain to me how to hide geometry but still have it affect the scene?

For instance if you use an emissive light on a plane you can uncheck "visible to camera" and hide that plane and the light is still affecting the scene.  NOW, if I wanted to have a physical ground plane but wanted to hide it from camera while still having reflections on my object how do I do this? This is stupid easy in pretty much every rendering package I've used but seems impossible in keyshot?????

Thanks

Offline kerembyl

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Re: Hide Geometry from camera?
« Reply #1 on: June 13, 2016, 10:22:37 am »
I actually don't know the easy solution but you might want to hear this one.

1-Uncheck part
2-Render scene
3-Re-check part and uncheck everything else except desired part
4-Render scene again
5-Import these two images into photoshop and erase your part but the reflections.

Maybe it's demanding process but hard is better than impossible right?

Offline JBird

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Re: Hide Geometry from camera?
« Reply #2 on: June 13, 2016, 10:46:04 am »
Thanks Kerembyl, unfortunately the whole point is to avoid photoshop all together for this sort of thing :/  If I have a hundred imagses to do and I'm running them through scripts I don't want to be photoshopping everything.  This is a function in every single render engine I know of except keyshot apparently...

For some reason the developers have decided such an important feature is not so important?

 

Offline TpwUK

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Re: Hide Geometry from camera?
« Reply #3 on: June 13, 2016, 04:37:27 pm »
I am guessing your example scenario just catches KS out so to speak.

Using HDRi as KeyShot does, there is a fake ground applied to create shadows/reflections, as far as i know, that fake ground can not be removed/hidden so when you deactivate your physical ground plane, the fake one takes over.

Martin

guest84672

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Re: Hide Geometry from camera?
« Reply #4 on: June 13, 2016, 05:08:51 pm »
Let's first understand what you are trying to do. Are you looking for the reflections of the environment in your object, but without the environment showing?

Offline JBird

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Re: Hide Geometry from camera?
« Reply #5 on: June 14, 2016, 01:55:30 pm »
@thomasteger- Yes this is what I'm trying to do BUT I want the reflections coming from actual geometry in this case a plane and not the hdr (ie pins).

guest84672

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Re: Hide Geometry from camera?
« Reply #6 on: June 14, 2016, 04:11:51 pm »
You may want to use the emissive material then. You can add texture it, and hide it from the camera, but still have it show in reflection.

Offline JBird

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Re: Hide Geometry from camera?
« Reply #7 on: June 15, 2016, 05:18:48 am »
Ok thanks I'll give this a try and get back to you. My only concern with using the emissive is that it emits light which I do NOT want it to do... I just want the environment light to interact with the plane via reflections etc.

Keep you posted.

guest84672

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Re: Hide Geometry from camera?
« Reply #8 on: June 15, 2016, 07:26:37 am »
At intensity = 1 it won't.

Offline JBird

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Re: Hide Geometry from camera?
« Reply #9 on: June 15, 2016, 08:34:33 am »
Yeah I think something like this is going to work just fine. Thanks thomasteger!

Offline bdesign

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Re: Hide Geometry from camera?
« Reply #10 on: June 15, 2016, 04:21:13 pm »
*EDIT* This is an updated revision of this technique. It is a minor change, but now works correctly with all objects, not just the ground plane.

Since the Emissive material does not receive shadows or reflections, the reflection of the physical ground plane on your object in this case will be basically a flat color representation. Here is a "trick" you may want to try. Apply an Emissive material as a label to your ground plane material. Uncheck all the options and set the Intensity to zero. Connect a Color To Number>(Opacity)Emissive, and set the "Output From" value to 1. Connect a Texture Map (any size solid-colored .jpg)>(Color)Emissive (I used a 1x1 pixel 50% grey). Set the Mapping Type to Camera, and the scale to 1 or just slightly greater in some cases (1.01-1.02). Depending on the curvature of the object and its proximity to the ground, there may be a very slight area that reflects the environment "floor" instead of the ground plane (you can see this just a very small bit in the bottom left edge of the cube in my example). This is minimized with non-square image aspect ratios, and the greater the Perspective/Focal Length in the Camera settings (my example is at default 35). As well, depending on the Inclination angle of the camera, you may need to slightly adjust the Shift Y of the Texture Map in order to avoid a "blank spot" in the reflection (I didn't in this example). To make the ground visible to the camera, just disable the Color To Number node. Below is an example setup.

Eric
« Last Edit: June 16, 2016, 08:15:34 pm by bdesign »

Offline LayC42

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Re: Hide Geometry from camera?
« Reply #11 on: June 15, 2016, 10:32:18 pm »
@bdesign

Your solutions are so awesome - I'm deeply impressed!

Good job

Offline bdesign

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Re: Hide Geometry from camera?
« Reply #12 on: June 15, 2016, 10:41:01 pm »
@bdesign

Your solutions are so awesome - I'm deeply impressed!

Good job
Thanks very much for your kind words, LayC42... I really appreciate them!

Cheers,
Eric

Offline JBird

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Re: Hide Geometry from camera?
« Reply #13 on: June 16, 2016, 11:42:50 am »
@bdesign

This is EXACTLY the effect I was after!! I will have to give this a try, thank you so much for this awesome help!

Offline bdesign

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Re: Hide Geometry from camera?
« Reply #14 on: June 16, 2016, 12:22:02 pm »
@bdesign

This is EXACTLY the effect I was after!! I will have to give this a try, thank you so much for this awesome help!
You're welcome, JBird! Glad to help. I love a good technical challenge :)

Cheers,
Eric