Incorrect Perspective Views. Distorted Proportions

[a.bowden]

Hi All,

 

I am having a problem with perspective views created in 2010. The problem I have is that my building has large eaves about 1200mm, and when rendered in perspective they are being elongated and stretched to look way out of proportion to how they appear is elevation. In perspective they appear more like 2000mm. Looks like the camera is stretching at the edges. I have placed the camera relatively close to the building, but have also tried moving it right out, and then zooming in, but that has made little difference. I am not adjusting the wide lines at all.

Does anyone know just how accurate the camera's are, because i need the perspective and angles in this case to very accurate.

Is their a way to fix this perspective distortion?

 

The red line in the attached image shows aproximately how much these peices should overhang. So the problem is that the image is stretched / distorted horizontaly. I have placed on the image a copy of the elevation showing what the true proportions should look like.

 

Thanks in advance to anyone who helps me on this problem.

[kippu]

could be because of the camera lens and also because of the eaves themselves , because they are projecting in front also

[Iain Denby]

I don't think it's anything to do with the camera. It's your perception of the amount of overhang, which is probably based on the one elevation that you show. But, you may be forgetting that the eaves overhang the same amount on the front as on the sides....which, in perspective, throws the corner of the eaves out from the building line more than the elevation suggests.

[shaneis]

I don't think it's anything to do with the camera. It's your perception of the amount of overhang, which is probably based on the one elevation that you show. But, you may be forgetting that the eaves overhang the same amount on the front as on the sides....which, in perspective, throws the corner of the eaves out from the building line more than the elevation suggests.

 

+1

 

Pythagoras tells me that along the mitre, it should be 1697mm. A 50mm camera will give a reasonably close approximation of the human eye. If you're dollying the camera way back and zooming yet still have this "distortion", then it is not a lens distortion. Try getting way back and using a 150mm+ lens length and double check your mitres are correct.. Remember too, that what our eyes see is a combination of lenses and our brain's interpretation/ correction whereas cameras simply give what comes through the lens.

[Iain Denby]

Guys

 

It's nothing to do with 'distortion'. If it was, then it would occur on the near right hand corner.

 

It's about your preconception (based on a 2d elevation that only shows one part of the overhang) and the reality.

 

You drew a red vertical line on the perspective where you thought the corner should be. How did you know where to draw that line?

 

 

Hmmmm....looking at the image again, it's interesting that the profile on the corner above the entrance is different, but yet seems to continue round. I'm wondering if this is a Loft and the corner is doing something strange. Check in the plan view to make sure it's correct.

Edited May 27, 2009 by Dibbers

[mattclinch]

it's a combination of a wide (90 degree-ish?) camera lens with the fact that you are looking at 45 degrees at the area where the eave turns a corner.

a bit of pythagoras shows you that a distance in line with a cross section or elevation and a cross section at 45 degree of the same distance (ie an eave turning a corner) will always be 1.4142.. times longer.

[Ernest Burden III]

...I have placed the camera relatively close to the building

 

Does anyone know just how accurate the camera's are

 

Is their a way to fix this perspective distortion?

 

The cameras are very accurate.

 

Having a camera close to your subject requires a fairly wide camear cone of view. Once that cone exceeds about 60 degrees you introduce distortion which will appear as lateral stretching of your view.

 

However, the real problem is that you are comparing an elevation to a perspective. Your view shows the corner at about a 45 degree angle (the line in plan from your camera position to the edge of the building) and you are therefor expressing the diagonal from corner of house to corner of cornice. Your proportion will appear as that diagonal would in a 45 degree-rotated elevation--about 1.4142x a straight-on elevation. It's not a perspective flaw, it's a design properly illustrated. If you shrink the overhang by the reciprocal of that, .7071x, you will see the proportion you expect.

 

Which do you want to show--the reality or a realistic impression?

 

EDIT--I didn't read the thread before writing this, just saw the first post and relied. Others' said the same things I did.

Edited May 27, 2009 by Ernest Burden