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Correcting Paralax Error and Composition

Jeff Mottle

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Latest work by my partner Mark Olson and I. Was rendered in Lightscape, modelled in AutoCAD ,and the RPC content and shadows were rendered in MAX and comp'ed over the Lightscape background plate in Photoshop. Let me know what you think.




[ May 15, 2002, 12:49 PM: Message edited by: Jeff Mottle ]

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Hi Jeff,


I like the atmosphere with the pavements and trees, but i think the cameraposition is a bit odd.

It's great to avoid parallax by keeping both the camera and the target at the same height (z- position), but it seems to me that the point of view is a bit weird/unrealistic, because the shot has been taken from half the heigth of the building.

This results in a horizon at half the height of your image and following some basic rules of composition this is never a good idea.

It is wiser to keep the horizon at 1/3 (1.33) or at 1.6028.


Unfortunately, trying to keep the horizon at 1/3 generates parallax, and most cgarchitects don't know how to handle this.


In viz4 you could use a modifier to correct this, but most other users don't know how to do it because their programs don't support this.

In one of the interviews on cgarchitect.com Mr. O'really talks about a program 'datacad' that can generate 2point perspectives. It sounds great, but since everyone is using another platform, not many will adopt this program of course.


I've been using a much simpler method to generate this for years. Here it is:


The only way to avoid parallax (without using a modifier) is to keep the z-position of the camera and it's target on the same level.

Unfortunately horizon will be at half the height.

The trick is to render a higher value for the height of the shot, and than eventually crop the image in photoshop, keeping the top/middle part.


To move the horizon up, a small calculation is necessary. Here is an example for an ordinary 640x480.


image height = 480

horizon = 240 (1/2)


if we want to move the horizon to 1/3, it has to be at 160 (480/3) from the bottom up, or 320 from the top down.

As - in a shot without parallax - the horizon will always be at 1/2 of the height, we will have to make the new height 320x2 = 640


so render the image 640x640, and then crop in photoshop to 640x480. You're shot will look much better with more skies visible and a better composition.


Here are some good rules of thumb:

For landscape shots render a square, i.e. the same height as width value.

For portret shots double the height value if you render.


Feel free to move the horizon to anything other than 1/2!


Great images allways start with good canvas sizes.

In my opinion a 640x400 (1.6) has a stronger feeling than a regular 640x80 (1.33)

Think about these before you plan your shot, and

portret shot without parallax of course!


Back to Jeff's image I would recommed to try this technique using a z-value of 300-500cm (i.e. half the height of the first floor).

Be sure to check the trees too, because the two trees in the front seem to have more depth than the ones to the right.


Looking forward for you're update ;)



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Looks great Jeff

Congrats on a job well done !


I like how you have broken up the monotonous windows, by changing the shutters and blinds.

The cars dont look too bad either, are they the new RPC Cars?


Nice lighting too, Contrast is really important to not make an image look flat, you should always be able to right click on your render, and find pixels that go from rgb=0 to rgb=255 to simulate a large dynamic range.


The only thing i can see that could be improved upon Jeff,

would be some 3D trees, your current ones stand out as very flat looking, and Repetitive.


Other than that, Thumbs Up ;)


[ May 18, 2002, 04:23 AM: Message edited by: Wolf ]

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I'm sorry but I'm not agree. I don't like the light. very yellow. VIZ sunlight problem mentioned in the forum heh... and. trees very green, shadows too dark, bad point of view.... mmmmm keep on trying. heh, just to spark off a little... it's easy to adjust biggrin2.gif

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