Panoramic Camera Match

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  02 February 2013
Panoramic Camera Match


We use 3Ds max to produce photomontages of proposed plant developments for the energy industry.

We model the development and then try to match it the best we can to a background image. This can be either a single photograph or a stitched panorama photograph. The field of view we have to cover is anything up to 180dgrees.

These images are not for interactive QTVR/ Panotour type output. Our end product is for flat printing for the purposes of public exhibition and environmental impact assessment reports. These photomontages are required to be verifiable and to match the geometry and perspective of the camera used to take the stitched images.

When matching to a wide-angle panoramic stitch we are finding it more difficult as we cannot find a way of getting 3d Max to have a projection output that matches the background image accurately.

Does anyone know of any techniques or plugins that would allow 3D max to project/match a model correctly against a panoramic image? Or are there any other programmes that anyone knows can achieve this?

We know it is technically, computing wise, possible as we use a programme called ‘Windfarm’ for wind turbine site assessments. This programme allows you to match model and DTM to up to 180 degree stitched panoramic images. It also takes into account earth curvature and atmospheric refraction. Unfortunately this programme cannot import other custom non wind turbine models.

In some methodologies there is a mention of VRAY using the physical camera set to cylindrical projection. We have down loaded the demo and are finding that the ‘Warped Spherical (Old style)’ projection seems to create a nearly convincing effect.

We are finding however that the overall width of the projection does not quite fit the position of existing objects in the panoramic image. This may be because the GPS data measurements are not accurate enough for the purpose. However we are trying to demo the ‘.lens’ file facility to see if that will help.

Does anyone know if using VRAY is the correct answer to this image matching problem? If so can you offer any advice that should theoretically make VRAY match exactly the geometry and perspective of a wide angle stitched panoramic photo?

Thanks in advance for any help.
  02 February 2013
What's wrong with mapping pano to a sphere and placing appropriately in your scene?

Are you using a nodal rig?

If you're having trouble aligning your spherical pano, you could use autodesk imagemodeler to accurately place multiple panos that were taken from different places in your location.

But if within Max you're using a rectilinear projection rendered from your stitching app then you should be able to match with regular max camera
  02 February 2013
Thanks for the reply MisterS,

I am not of what you mean by ‘mapping the pano to a sphere and placing appropriately in the scene’. I have mapped images to the interior of a sphere before to create a sky dome. Are you meaning something similar to this? I also have had a look at some Imagemodeler documentation/videos and I am not sure how it could help. Any chance you could flesh out your meaning of the two processes?

Yes the photos for the panorama were taken with a nodal rig. They are stitched to a cylindrical projection within ‘Autopano’. This is because the end images are not for interactive pano tour type output and need to maintain perspective /geometry as near as possible to that perceived by the human eye in real life. Camera specification and projection of stitch are specified in ‘SNH Landscape Visualisation Guidelines which we have to adhere to, so the end projection must be the same as the original cylindrical panorama stitch.

As far as I can see a rectilinear projection stitch gives a massive distortion to objects on the outer edges of the panorama. Is there a way of getting the image back to non-rectilinear after matching the proposed infrastructure and rendering out?
  02 February 2013
Use a spherical stitch rather than cylindrical. Then create a sphere/skydome like you said. Then place a camera at the centre of your sphere and adjust its settings (rotation, focal lenghth but not transform) to you're liking.

This camera must be aligned to centre of you sphere. And it will look correct when you render and will match your geometry if you place your objects correctly providing you have a good stitch.

I've done this in max. Gets trickier if you want to bake your panos to your model in max if you have multiple panos.

You can use rectilinear - this is real world perspective but if you go super wide you will get distortion but should still match a really wide Max camera but try spherical first, you're then free to rotate and zoom.

My reference to imagemodeler was in case you needed an accurate way of placing you pano locations relative to each other. Ie calibrate them. You can also accurately model from your panoramas or still photos. And have a reference point for placing proposed geometry correctly in world space. I compared photogrammetry with a laser scan once and it was within 5mm so very cool technique.

Feel free to ask more questions.

Gnomon make some cool DVDs on this subject, look under digital sets. Done in maya though.
Google 'Scott metzger HDR mari fxguide' which is also cool. Would post link but am on my phone.

Last edited by MisterS : 02 February 2013 at 09:23 PM.
  02 February 2013
The accurate way would be to match the source/non-stiched images and then build the panos after the fact. There will be a greater margin of error on the actual pano, because of the match and stitch process.

"The Evil Monkey hiding in your closet."
  02 February 2013
But the stitching process itself removes the distortion, and it bases calculations on multiple images to get a more accurate solution.
  02 February 2013
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