Help ugently needed in compositing an exterior shot for ach viz

[Newb47]

Hi, I'm kinda new to this forum (or actually forums in general). Also arch viz.

I urgently need help with compositing a synthetic model of a proposed building into a photo using camera match in 3DS Max, Vray and a HDR lightprobe I've made. The problem is that I cannot get a good camera match as the background image is a stitched panoramic image (using PTGUI). I'm quite new to setting up a architectural visualization so any help is greatly appreciated. I've attach the panoramic image of the background (the building site) and the proposed building, so feel free to comment as how you would go about this project. Thanks

[WAcky]

Hi Sam and welcome to the forums.

 

Do you by chance have the site survey data (if a site survey was completed)

 

If you have this data you may be able to do a camera match based off the building on the right but even so it will be difficult due to the lack of any ground plane reference.

 

The distortion towards the edges of the screen is getting pretty big so matching this could be a difficult one, yes.

 

Another thing you could do is to get the exif data from the photographs to match the camera in 3ds max which could get the match close enough to be able to tweak in photoshop...

 

I've never tried camera matching with a stitched photograph but others may have and might have a better idea than me.

 

Good luck!

[Stephen Thomas]

I've recently been doing some camera matching for visual impact studies and thought I'd pass on my experiences with it. Like you I was given stitched panoramas to work with, though I also had the individual photos, gps reference and bearing data too.

 

The difference between a stitched cylindrical panorama and a wide angle lens is that the horizontal lines will curve depending on how far from the horizon line they are. You can see this curvature happening in your background plate. Therefore you must use a cylindrical camera type in max rather than just pushing the lens angle wider. The way to do this is to set up a standard cam and then use the vray camera override in your render settings.

 

The first step is to figure out the position of the camera which took the shot, if you don't have this you could maybe figure it out from a street plan. Then you have to figure out your horizontal FOV or field of view. To do this look at the EXIF data for the images and note the focal length. You may need to apply a focal length multiplier to this if it was not a full frame 35mm camera. Then input this lens data into your max camera and note the resulting FOV. Say for example the FOV was 44 degrees and you worked out the panorama was 2.5 times the width of one of the individual photos then the resulting FOV would be 110 degrees.

 

Now input the value of 110 degrees into your vray camera overrides and choose the camera type called 'Warped Spherical (old-style)'. If you choose the Cylindrical type for some reason it squashes the image vertically, but this type works perfectly. Also input the dimensions of the panorama as your render dimensions.

 

Unfortunately you don't get a viewport preview of what the final render will look like so a bit of trial and error is needed to get the camera pointing in the right direction. What I did was to crop a 4:3 area from the centre of the panorama and then use this as a viewport background to align the centre point of my image. I only had landscape as reference but if you also roughly model the buildings to the right then this might help in your case to line things up. You may also need to rotate the rendered building slightly in Photoshop to account for the tripod not being level etc but the main thing is to get the perspective of the building correct.

Edited July 19, 2009 by stef.thomas

[Newb47]

Thanks for the idea on cylindrical camera in max, I will try that tomorrow. I have modeled the building to the right, unfortunatley the plans I drew them from are abit out-dated, which might have caused additional errors in camera matching.

 

Here's a draft composite I did just now, as you can see there the building doesn't quite match up. Since the background image is quite warped at the sides, the building actually seems shorter than intended on the plan.