about fps camera

Mirror · Post by **Mirror** » Wed Dec 19, 2007 9:29 am

hi. i have noticed that in the fpscamerascenenode, it's plane is always horizontal. is there any way to change this ? I want this because im trying to "walk" on a "planet" but if i go below the equator, i can't rotate the camera down, because it's already more than 90 degrees. In other words, what i want is having the plane of the camera, always perpendicular to the vector camera->getPosition(). can i make this with the fpscamera or i must code a custom one ?

JP · Post by JP » Wed Dec 19, 2007 10:04 am

I think you'll have to make your own custom camera, though i would imagine it wouldn't be too much code to change so just copy the code from CCameraFPSSceneNode.cpp in the source folder and make the necessary changes.

shogun · Post by **shogun** » Wed Dec 19, 2007 10:20 am

I wonder if it would be wiser to rotate the planet instead.

Mirror · Post by **Mirror** » Wed Dec 19, 2007 10:24 am

shogun wrote:I wonder if it would be wiser to rotate the planet instead.

no, because i want to attach the camera to a player, and wouldn't also want to rotate all existing objects as well

christianclavet · Post by **christianclavet** » Wed Dec 19, 2007 1:32 pm

If you want to do this, you will have to create your own camera controller.
All camera can use a UPvector. So you define the angle and put the UPvector and the camera will be aligned to it. It will be relatively easy to make that. But the mouse movement are not following the upvector.

A better alternative (as Shogun talked about)would be create a empty node then use it as a parent for the whole scene and rotate it on the direction needed. The camera and player would need NOT be parented to this empty node for this to work.

Mirror · Post by **Mirror** » Wed Dec 19, 2007 2:31 pm

christianclavet wrote:If you want to do this, you will have to create your own camera controller.
All camera can use a UPvector. So you define the angle and put the UPvector and the camera will be aligned to it. It will be relatively easy to make that. But the mouse movement are not following the upvector.

A better alternative (as Shogun talked about)would be create a empty node then use it as a parent for the whole scene and rotate it on the direction needed. The camera and player would need NOT be parented to this empty node for this to work.

wouldn't this approach be very expensive ? imagine thousands of objects needed to be rotated. plus, that if i need a multiplayer game, this is not a good solution i think.

p.s. where can i look about the upvector ? the irrlicht help file doesnt seem to have a reference on this.

JP · Post by JP » Wed Dec 19, 2007 2:49 pm

You would only be rotating the parent of all the rotatable objects which would not in turn apply rotations to all the children, instead their absolute rotations are calculated based on the rotation of their parent.

christianclavet · Post by **christianclavet** » Wed Dec 19, 2007 3:19 pm

All the items will rotate anyway in the camera. So I think it would be about the same. (It would be calculated for change only on the parent and not the childrens (that have their own local coordinate system). It shoulnt be calculated twice.

Unless there some culling algorithm in there that does this (frustum culling).

rogerborg · Post by **rogerborg** » Wed Dec 19, 2007 3:56 pm

If you're actually writing a game rather than a simple disposable demo, do yourself a favour and forget about the built in cameras, and for that matter the Irrlicht event system. They're only really suitable for demos, and you'll spend more time trying to work around them than you will writing something that's actually suitable for your requirements. IMO.

Mirror · Post by **Mirror** » Wed Dec 19, 2007 7:44 pm

thank you for your answers guys

mqrk · Post by **mqrk** » Thu Dec 20, 2007 4:30 am

I think this has already been covered but I just wanted to clarify that the up-vector is not handled by the fpscamera to suit your needs.

I played around with it a bit and it looks like moving your mouse up rotates the camera in the original "up" direction (what would now be "left" or something).

You might just copy the CCameraFPSSceneNode class and change the Animate function to factor the up-vector into the calculations. I'm not really sure how to do it but I'm pretty sure that's where you start.

christianclavet · Post by **christianclavet** » Thu Dec 20, 2007 5:27 am

mqrk You are talking about the source of the FPS camera. And it surely cannot be used like that (I know. I had to retake and adapt the code so it can work.) For the UPVector, you are wrong. This is a feature on all cameras (Normal since it was created for the standard camera and that the other camera inherit the STD Camera class.

For example, to reverse the camera view upside down:

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camera->setUpVector(vector3DF(0,-1,0));

This should take your camera view and have it upside down (For Any camera definition you have (FPSCamera, MayaCamera, or STD camera)
You should move the right way, but the mouse rotation will be inverted.

What he has to do is to take the CCamera source as a reference point(or download my current code for the FIRST KING), and do some math so that mouse movements will rotate the camera the right way.

The moving part is accounted for, in the source, it's using the UpVector of the camera for the calcultation (Strafing), it should "strafe" the right way. It's only have to do some calculations of the mouse move increment of the relative rotation of the camera relative to the UPvector. So the relative movement is going the right way.

So you could take my current code for FIRST KING project and take the part of the camera and implement this (Align the upvector of the camera with the relative rotation based on the mouse movement). Or do what we suggested previously. If you are very strong in math, physic and expert at programming, I would recommend the same thing that proposed RogerBorg.

But starting up with IRRlicht could also be good, if you need a prototype fast for a "proof of concept".

Mirror · Post by **Mirror** » Thu Dec 20, 2007 2:25 pm

thanks for your reply christian and mqrk.

my first step was using

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camera->setUpVector(core::vector3df(loc.X, loc.Y, loc.Z));

this assuming that the center is (0,0,0) updates the upvector to be perpendicular to the plane that is tangent with the planet in the intersection point of the line (0,0,0-x,y,z) with the planet.

( or simply put, aligns the upvector with the (0,0,0-x,y,z) vector ).

but as you previously also said i have to tweak the fpscamera code for the mouse movement ( it doesn't work correctly, doesn't update ). i will look also your code ( the first king ) and post in this topic any good results.

@roger, im still on my initial steps though but yes you are right.

i hope my studying maths will help me on this

Mirror · Post by **Mirror** » Thu Dec 20, 2007 8:41 pm

i think i have found a workaround about this issue.

from CCameraFPSSceneNode.cpp :

Code: Select all

const f32 MAX_VERTICAL_ANGLE = 88.0f;

if that is changed to some huge value like 3600000.0f then it will solve the problem.

( needs recompile i think )