Perspective Camera functions incorrectly.

vitek · Post by **vitek** » Thu Oct 11, 2007 5:02 am

I'm giving an example as to where the issue of only one plane near/far is being used.

All perspective projections that I've ever seen use this same system. The zNear and zFar distances are to a plane perpendicular to the view vector. You're not showing me anything new.

You even said yourself that you found that gamemaker doesn't do it this way

No. I said the opposite of that. GameMaker does exactly the same thing that Irrlicht does. It applies a view and perspective projection matrix.

how can you say that none do

Because, as I've been trying to tell you, the problem is with perspective projection. If you use a perspective projection matrix the artifact you are complaining about will appear.

All of the perspective-based cameras are like this in that they only take into consideration the depth in the direction you're looking!

Yes. Not just the cameras in Irrlicht.

VioletAlixe · Post by **VioletAlixe** » Thu Oct 11, 2007 6:16 am

Okay, regardless of what the other engines are doing, that article you sourced has no sources of its own that are reliable, and it even states so at the top. If you look at a "perspective corrected" picture, you get an otho view with depth in only one direction. Hence the current camera. It is useful if you want to design something without the interference of perspective (3d modeling for example). It however is not realistic in that our eyes and consequently our real cameras perceive in a "perspective distorted" manner.

EDIT: More importantly, not only is it not realistic, but it's also not accurate, because perspective is relative to all three planes. The current camera is a pseudo-perspective camera in that it mimics perspective. (Yes, it accurately replicates other "perspective projections" in use in many games today, but it does not replicate true perspective as seen in real life.)

hybrid · Post by **hybrid** » Thu Oct 11, 2007 7:57 am

So then please give us a replacement metrix which provides a different, but still useful projection matrix. If we get just another one which can be chosen from those matrices it's fine. But we'd need to see a picture rendered in Irrlicht which shows some substantial difference to what we now have, and it must be useful for more than one person. Obviously, no one except you does understand what you're trying to do, respectively knows a way to overcome this limitation. So show us a way to overcome it (in Irrlicht!) and the rendered results.

rogerborg · Post by **rogerborg** » Thu Oct 11, 2007 8:01 am

[Oops, sorry for duping your post, hybrid]

Also, can you identify any games or applications that currently use a 'correct' perspective camera?

VioletAlixe · Post by **VioletAlixe** » Thu Oct 11, 2007 8:17 am

Sure thing; let me compile a bunch of resources then and I'll post them all here when I'm certain I've done both the things you're asking for.

christianclavet · Post by **christianclavet** » Thu Oct 11, 2007 9:27 am

VioletAlixe..

I think your asking for a realistic lens simulation. Not sure the calculations made by the engine would reproduce that in detail. It's good enough for games and some applications. If you want that the system account for every details of the lens curvature/lens refraction index/light absortion/diafragm size... I don't think it's there.

But if you'd want to simulate a lens in the detail. You would have to work on some projection system that's will have to process this.

Do you know of any game that as that kind of realistic simulation the type you mention?

VioletAlixe · Post by **VioletAlixe** » Thu Oct 11, 2007 9:53 am

Chris, please hold questions until I respond to the above. Yes it's do-able, in fact it's not very hard to do at all. -And yes, I know of some, which I'm going to list as a response to the second question. I'm going to post it all together soon.

sRc · Post by **sRc** » Thu Oct 11, 2007 8:47 pm

you have a solution? I spent days messing with things to no avail when I last looked at this (bug report), gave me a headache

VioletAlixe · Post by **VioletAlixe** » Fri Oct 12, 2007 12:40 am

The Anaconda wrote:you have a solution? I spent days messing with things to no avail when I last looked at this (bug report), gave me a headache

To fix that weird look of the sphere, you have to correct Irrlicht's default FOV. Just set the FOV to (45 * irr::core::DEGTORAD). Should work fine. I'm still working on the matrices for the perspective though. - Also, once I do finish it, that artifact should no longer occur.

rogerborg · Post by **rogerborg** » Fri Oct 12, 2007 1:21 pm

VioletAlixe wrote:
The Anaconda wrote:you have a solution? I spent days messing with things to no avail when I last looked at this (bug report), gave me a headache
To fix that weird look of the sphere, you have to correct Irrlicht's default FOV. Just set the FOV to (45 * irr::core::DEGTORAD). Should work fine.

Using a 45 degree FOV (and the same 1280x720 screen as the original).

sRc · Post by **sRc** » Fri Oct 12, 2007 2:22 pm

rogerborg wrote:
VioletAlixe wrote:
The Anaconda wrote:you have a solution? I spent days messing with things to no avail when I last looked at this (bug report), gave me a headache
To fix that weird look of the sphere, you have to correct Irrlicht's default FOV. Just set the FOV to (45 * irr::core::DEGTORAD). Should work fine.
Using a 45 degree FOV (and the same 1280x720 screen as the original).

yep, thats why I went to altering the matrix, but could never get it to work

VioletAlixe · Post by **VioletAlixe** » Sat Oct 13, 2007 3:21 am

Alright, I've almost succeeded so far. I say almost in that I'm able to account for half the directions necessary for this perspective. I can't do the other half with a single matrix4. Working on it as I type. Will update soon.

rogerborg · Post by **rogerborg** » Tue Oct 16, 2007 10:57 am

Is there anything that we can do to help with progress on this?

rogerborg · Post by **rogerborg** » Sat Oct 20, 2007 10:53 am

Yes it's do-able, in fact it's not very hard to do at all.

Care to revise that answer?

VioletAlixe · Post by **VioletAlixe** » Mon Oct 22, 2007 9:56 pm

rogerborg wrote:
Yes it's do-able, in fact it's not very hard to do at all.
Care to revise that answer?

I've done it so far, but it required so many rewrites I can't recall all the files I had to change. You can't do it with a single view matrix, you have to change how it's specifically drawn to the screen by section. Which, mind you, ended up rendering too slow on my computer to be worth implementing.

I ended up just making it a pre-run-time vertex processor. If you want the formula to do so, I can give it to you all.

Just render the individual vertex at an additional distance on the z axis based on the distance formula times the strength of the lens.

Frankly, modern home computers can't handle a realistic reflex lens smoothly. However, if you'd like to see one in action, keep an eye out for the PS3 debut of FFXIII, where the CG is rendered in real time using one.

Sorry for the let down, folks.