reflection of scene in mirror with slight differences between scene and reflection

sriesch

What would be the best way to create a scene that includes a freestanding mirror in the middle where the mirror reflection has slight differences from the scene, but still appears to be a reflection of most of the rest of the scene? As an added complication, I wish to do this without postwork (contest rules).

I think there was a thread where this was mentioned already, but I'm unable to locate it.

A few things occur to me offhand, but perhaps there is a better or preferred way.
If I wasn't trying to avoid postwork I could try to make two versions of the scene, and simply cut and paste the mirror reflection from one scene to the other, but I don't think I can do that reasonably without postwork.
Another option would be to not even have a mirror, but to have a mirror frame and mostly duplicate the scene behind it. However I think that will be a lot of trouble since lighting has to match the "reflection" angle without spilling through the mirror frame opening and affecting the lighting from a different angle in the other half of the scene.
I bet I'm making this way too hard and there's something really simple I'm overlooking... ideas?

Herald of Fire

How 'different' do you want the reflection? That's sort of a key point in how you'll need to compose the scene. What you're trying to do isn't going to be easy without postwork in either case, but it might help with the solution.

Jaderail

Which Contest? Is it the DSA Refelections one?

Chohole

Pre work instead of post work ? Render the 2nd scene and then use it on the mirror plane as a tex instead of just a mirror surface. Slightly faded and a tad fuzzy even maybe. render that scene with the light exactly opposite the light direction in the actual scene? Actually thinking about it, just reversing the image would do that.

Renpatsu

You didn't specifically say what kind of differences you are looking at, so not sure if this helps. Depending on the differences you are looking at it might be (almost) impossible to do that during render time directly, but postwork should do.

If you just want certain surfaces or objects (if you alter all of the objects surfaces) to not to appear in the scene but in the reflection, this can be done with using uberSurface shader and the "Fantom" setting on the surface tab set to "On". Basically "Fantom" makes the surface disappear in the the direct view of the camera, but the surface still reflects light and due to that still shows in the mirror. You might still need to tweak as for which surfaces/objects cast/accept shadows etc. to achieve the look you want.

When the differences are more complex, then I would perhaps aim for two render passes, e.g. use the "Fantom" technique above to get a clear image of the mirrored reflection how I'd like it to appear and then do a second render with the objects altered and not using "Fantom". Within e.g. GIMP or photoshop (or other similar programs) it should be possible to merge the two pictures then as you see fit.

There are other ways certainly, but I usually use "Fantom" in some form on such occasions.

Edit to add: You can also use "Raytrace" surface setting to "Off" to have something disappear from the mirror, but still being in the scene. The picture with the brighter mirror image is showing both "Fantom" set to "On" on the blue sphere surface and "Raytrace" set to "Off" on the red cube.

sriesch

@HeraldOfFire and Renpatsu, the scene would be a room interior, including a freestanding mirror, with a figure in front of the mirror. Everything in the scene (that's in view of the mirror) would be reflected identically except for the figure, which would have differences between the actual figure and the reflection. To further complicate matters, the mirror is actually one of those with multiple panels at slightly different angles, and my idea was to have one panel be different from the others. (And I've just realized that I can see one mirror panel's reflection as a reflection in another panel... argh... I might be able to change the angles to avoid that though.

@Jaderail, the contest is the April challenge at Dreamslayer Artworks, http://www.dreamslayerartworks.com/vB3/showthread.php?7797-Daz-Challenge-April-Mirrored-Reflections .

@chohole, to reverse the scene to use as a reflection I'll need to actually see it looking from the opposite side of the mirror (the side I can't see in the render normally), so I'd have to put a camera on the other side and make the mirror transparent, then render. I haven't tried that yet, it might be tricky lining it up since the mirror is within the scene and not containing the entire scene. However doing that and then using it as a texture in place of the mirror surface might work; I won't even have to cut it to the mirror size and shape since I can use tiling at values less than 1 to zoom in or out and adjust it up/down and left/right until it matches where it's supposed to be.

@Renpatsu, that Fantom parameter is a good idea for adding additional items into the reflection but not in the scene itself, thanks. I'll have to go research how to use UberSurface merged with an existing texture (V3 maps, etc.) One problem is the added self-imposed complication of multiple mirrors, since then the surface would be identical in all mirror panels. I might rethink my design idea though, it's not set in stone yet.

Jaderail

I'm a Member on DSA and the rule that matters is this one...

5. multi renders composted together is allowed as long as they don't contain what is considered post work as stated above.
(when compositing images rendered in layers - blend layers-will not be allowed such as multiply and overlay- does everything needs to be brought in as normal to show lighting achieved in daz)

A Normal Layer is allowed. You would Need to USE the SAME lighting for BOTH layers but it IS allowed If done this way.

Jaderail

I just got a Answer on the DSA Daz3D contest. Layers are allowed as long as they are Normal layers and that no layer has had any Postwork done to it. You can not use any BLEND mode at all. Each layer must be a Daz Studio render unaltered in any way. If asked you might need to prove it by posting each layer used as a single file. So keep all your different renders/layers until after the contest has ended or your work has been accepted. I would go with until after the contest ends myself just to be safe.

I hope this helps you some.

EDIT: You can ignore the Lighting thing in the Last post. As long as its a Normal Layer with no postwork you are fine.

Mattymanx

Several ways to alter the reflection.

Diffuse Colour
Reflection Colour
Use a bump map
Use a Diffuse map
Use a primative plane with a bump map and diffuse map and make it somewhat transparent and place it in front of the mirror.

ps, Raytraced depth of 2 shoud be all you need unless there are additional light bounces you need to show between reflective surfaces.

Eustace Scrubb

Of course, the Single Pane Mirror would be the easiest to do by any method. But it occurs to me that if you duplicate/near-duplicate the scene across a "mirror" window it will actually be to your benefit to let the light spillage occur (unless raytraced reflections are explicitly a contest requirement) because real mirrors reflect light, not just images, and you're NOT going to get that from a regular DS/3Delight mirror render. So your best bet is, in my opinion, a perfectly mirrored scene on each side of a refractive glass (the "reflection" ought to be from the silvering on the back-side of the glass) and let the light from the reflection light the figure's face as it does in your own bathroom. Then you can fine-tune whatever's different about the reflection scene and still have a more realistic reflection than almost any other contestant whose mirrors don't bounce light.

Good luck!