On 3d Environments

[Guest EricFoy]

So here are my latest discoveries...

You can use a wide variety of photos for a 3D environment by simply padding them with the right colored pixels in the right places.  Here's what I've found:

First, make sure the picture has a 2x1 aspect ratio overall -twice as wide as it is tall.  This is because the spatial sphere upon which it gets projected is 360 degrees "wide" and 180 degrees "tall".  The padding that you put on the top becomes a circular field at the zenith, so choose a color (usually sky blue or so) that will provide the right approximate lighting effect that you are looking for in the final rendering.  The padding you put at the bottom becomes a circular field at the nadir, so usually a darker color is in order unless you are going for a special effect of some sort.  The light coming from this source will only affect the rendering of the bottom sides of objects in the scene, or in some cases the tops of objects that are below a reflective surface.

In the following scenes,  I grabbed a 180-degree pano that I shot (above) while vacationing in italy last year (I highly recommend Tuscany -the people are friendly and the wine is good).  The second image here is my padded version:

Now here's the cool part.  You don't need a full 360 degree panorama to get pretty good results.  Just make sure the picture has a 2x1 aspect ratio.  This will get you pretty close to a proper perspective. Also, it is important to pad the top and bottom such that the horizon in the original lands at the vertical half-way point in the final image.  This will properly project the horizon of the image onto the horizon in the spatial sphere.  You can deviate up or down to fit your rendering subject, placing it at your desired elevation in the photo, but note that this results in a perspective conflict and you can only get away with so much of this.  Trial and error rules here.  I may be wrong here, but I think that if you want to render, say, a car from a bumper-height angle, you really need a 3D environment image that was shot from bumper-height.  The greater the disparity between the two, the more work is required in terms of modelling the floor or road that the car is sitting on.

Anyway, I got kind of excited about these renderings, so I thought I'post 'em:

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Looking at the reflections in the sphere shapes, you can see in a few places that my panorama doesn't stitch properly on the "backside".  This all seems pretty much okay to me, since few people other than us renderers would ever catch on to what was going on there, and it hardly spoils the realism of the shot.

Anyway, these were rendered with no lights in the scene, and zero ambient light.  I am particularly impressed with how the shadowing came out inside the cup areas and on the top of the pedestal, below the widgets.

By the way, these renderings each took about ten minutes. Not bad, I thought. I think it speeds thing up when you turn off all the lights.

Edited July 17, 2008 by EricFoy

[swallis]

Wow, I'm impressed! Those look great, and thanks for taking the time to share your discoveries.

 

Scott

[tlehnhaeuser]

Eric WOW!

Nice!!!

Atatched is my first attempt. It never dawned on me to not use any lights at all and get such superior results.

Thanks this help tremndously.

Tom

 

[Cary OConnor]

Good description and details.

 

The GI works well with out extra lights since it can use the 3D environments to cast lights.

 

Cary