From Orthographic Camera To Perspective

[legie]

Hey,
I am trying to simulate an orthographic camera with an perspectiv one and then to have a smooth transition back to the 'normal' perspective camera.

What I have so far:

"keyframe A" sets the perspective camera's focal length = 2055, which turns the angle = 1 and therefore fakes an orthographic camera; with the camera's postion at 0,0,100.

Then I have "keyframe B", which sets the camera's focal length = 41.1 (1/50 of the original length) and the camera's position to 0, 0, 2.25 (here I thought the z-value would be 2 (1/50*100) but it's not for some reason...) "Keyframe B" places the object in exactly the same position as 'Keyframe A' but with a perspective camera.

The problem is that the transition between A and B is not linear (as it is based on a lens I guess) and I don't know how to set keyframes for the focal length in order to fake a linear transition. Does anyone know the math Maya is using for this?

OR: can I keyframe the little button "orthographic" that cameras have??

Thanks for some help!!

[joojaa]

ahh no doont do this like that it may glitch.

Anwyay theres a trick to this and thats to recreate the camera inner workings. heres the tip, your in luck since i jut made this for explaining how the 3d camera works, it so happens it does just this:

http://users.tkk.fi/~joojala2/highend/3DCa...rksLikeThis.mov

(a real 3d camera reads it just like the picture in front, ah this also explains why you cant have a 0 clippingplae because 1/0 is a bit problematic)

[legie]

hmm...nice trick! I am not sure it will work for me though as I have a large scene with many objects and after the orthographic camera is turned into an perspective one, the perspective camera moves 'into' the scene and gets close to objects and moves inbetween them.

But I just had an idea: I start with an orthographic camera, do your scaling trick for the transition and then switch to an perspective camera. That should work, no?

Thanks as usual!!!

[legie]

One more question: how do I know how to exactely scale my objects?

[joojaa]

well first of its not a trick, this is how the images you see on the screen are done, quite exactly at that. You odnt actually need the latices i just did it to show what the matrix operations do in friendly terms.

scene size does not matter

QUOTE
the perspective camera moves 'into' the scene and gets close to objects and moves inbetween them.

no problem thats what the clipping planes are for just move the ortographic front to 0 0 0 and set the clippingplane to 0.1 or something, and it will clip whatever you have in the scene.

However it depends on what you render too. And what with.

[legie]

hmm...if not with latices with what should I do the scaling then?

Thanks!

[legie]

yeah...I need more information about how to scale/deform my objects. I tried a lattice and I am not getting the same as the view of the perspective camera...?

[joojaa]

matrix

[legie]

hmm...I tried to look up what you might mean but I am not getting anywhere. Could you explain a little further what I need to do, please? I know what a matrix is and the math around it but I don't know how to utilize one in order to deform my scene?

[legie]

please help...
Could at least someone point me to keywords, tutorials, etc. so that I could look up myself what to do with matrices in order to scale my scene? Is it done within MEL?

[joojaa]

http://www.cs.kuleuven.ac.be/cwis/research...n-3d/node8.html.

no a node!

[legie]

thank goodness, you are back...:-)! Thanks for your answer. The math is not so much the problem but the implementation of it in Maya. So you are saying with a node...hmmm...I have to investigate that...

[joojaa]

sorry i was celebrating the nightless night as is the custom over here. It also threw my internal clock off by a 3 hour period.

[legie]

don't be sorry!...it's just that this forum is not the same if you are not around...

Anyway...
I do need more help with this, I am failing in the details. Here is what I have so far...

Problem: I want to scale objects in a way that it looks through an orthographic camera exactly the same way it would look through a perspective camera.

Solution: Multiply every vertex (?) with a perspective projection matrix

Approach (sorry for my crappy note):

Questions:

-Are my near and far values exactly my clipping plane values? ( in my case n=0.001, f=10000)
-Is my width based on the orthographic width of the camera? ( Orthographic width = 8 -> right = 4, left = -4)
-Can I derive the height from the aspect ratio (1.333) and is therefore 6? (-> top = 3, bottom = -3)

-I am confused by when I need which coordinate system. My camera is located at (0,0,0) facing down -z and the up-vecor is y. Then I don't need to transform my object into the camera space anymore, right?
-How about the single coordinates from the vertices? They are all in object space and I need to convert them to World-space, right?To make them homogeneous I just add "1" as forth coordinate -> (x,y,z,1), right? Do I have to transform them any other way in order to use them in the perspective projection?

-How do I read in all vertices' coordinates and apply the projection matrix to every single one of them?

Thanks!

[joojaa]

so that others can follow this too, what yopu do is you plunk in the matrix into a defromer (any deformed but lattice is easiest to operate, but screws normals up, c