General questions looking for an answer

[hola, bueno, basicamente me han desterrado del foro general al de oFusion asi que os posteo aqui lo que habia puesto en el otro, había intentado retirar de forma general las referencias a oFusion para intentar obtener otro tipo de respuestas, pero enfin... Bueno, ahora lo posteo tal cual y luego ya hare un edit, porque escribir en ingles me cuesta un poco y ando con prisa]
Hi.

I´ve been playing with oFusion and Ogre to check the viavility of making my university final project with it.

After some weeks I´ve some questions:


(1)question about objet file formats
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I´ve found that we have the:
.mesh--> a .mesh per single geometry
.scene--> a file that can have a number of .mesh files inside.
.osm (oFusion scene)

.mesh for me is unusable, since each objetct I model in a 3Dsof has lots of 3D single geometries that form it.
For example a building has botton, medium and roof areas, and each area has from 4 to 20 geometries.

.scene is the file I think I´ve to use, since I´ve explained before each objet is created by several geometric models.
But is the .scene oriented to this kind of objets with multiple geometries or is oriented for generating scenes with multiple .mesh files imported inside of it?

Can I have any problem using the .scene files as the format for my buildings and also use the .scene file format for the file that would include all those buildings creating a sector of my city?

--> now with the GOOF starting to come to live, do you think that exporting or converting from max to .mesh/scene etc is wasting time, does anyone know if

these formats will be able to be imported into goof?


(2)x-ref objets are posible?
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Has ogre anything like the x-ref´s (in max) inlines (in vrml)... etc?
something that calls the objets like buildings, lights, cars that would be away from the scene?
--> anyway if ogre has not, sure the oncoming projects like goof will have something like that, so I´ll send my proposal to those project leaders of the features that have to be taken in mind so that from my point of view are important.

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So once reached this point one of my main question is how do you recommend me to focus the creation of large scenes with a considerable amount of objets,

(always trying to make it the most of the work from a 3D packaje, since my strongest skills are on 3D modelling).
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(3)LOD & shadows
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whell, I know that in ogre we have geometry LODs and for textures a "LOD" that makes them appear blurry & low res from certain distance making the world run smoother.

whats the name of this texture "LOD" technique?

Does this texture "LOD" make unnecesary the creation of low res textures in photoshop as I´ve been doing till now for maping the first level of my geometry LODs?.

Can this "LOD" be controlled so that certain textures as the facades stay hi-res longer(farther) than others?

And about the shadows&LODs
Making tests to check a possible performance of a large scene, I duplicated a building several times (near 50 detailed tower buildings) and started to move

the camera. It ran ok when no shadows where in the scene but when activating the shadows everything got slow slow.

So I think one solution could be to make a geometry LOD and aply a material to this objets that makes them not to cast shadows. I know it is posible in ogre

as I´ve done this with oFusion, but somethig nice whould be the following:

As the shadows give very nice effects (even a simple rectangular shadow) would be interesting that buildings could keep casting shadows even if they where quite far, so I think a couple of things could be done.

1) Make the greater part of the building in the 1st level of the LOD cast shadows.
--> This has the inconvenience that a certain distance rare effects could happen as if the botton areas dont cast shadows some parts of the street would be lit "wihout logical reasons"

2) A geometry that would be the one casting shadows but not the one being rendered. Something like the collision geometries, that make the collision calcules easyer...
So, a high-rise building that has a rectangular shape would be casting shadows of a renctangle geometry that would not be rendered.
I think this would be very interesting (if doesn´t exist yet for ogre) since we could define wich shadows and their shape are rendered at a certain distance
(also posible for a near distance, but for near distance we would be wishing to see the full detailed shadows, I think)


(4) 2 geometries located at the same Y.
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well, trough the street we´ve objets placed over the asplhast, the sidewalk.. etc
if the objetc placed on the sidewalk is a simple plane, as could be a plane with a texture of a horizontal road sign, there will be a problem-->the engine will ask himself wich objet must be rendered.
Till now I´ve solutioned this easylly just by elevating the objet slightly from the pavement, but this technique make this element fail or not to be
represented at med-high distances.
So, has Ogre a render priority? or something similar so that I can asign to the objets properties as "level 0" for the sidewalk and "level 1" for the
plane-object.

well, some long questions/coments posted.... I´ve more but I thinks they are enough for a single post

Hope you find the themes interesting.
bye__

oFusion produces "osm" scene files, i can comment on them, but for the other formats you may want to ask in the proper forums


(2)x-ref objets are posible?


Ogre uses entities, that in fact are x-refs of meshes

oFusion will create and export the instanced objects you want


So once reached this point one of my main question is how do you recommend me to focus the creation of large scenes with a considerable amount of objets


Very project dependant, its up to your method of working and how you like or prefer to create them

There are no single way of doing your work, i dont have the free time to provide you with pointers on how you should prepare or do your work (and not without a detailed description of what you want to do), but maybe others can provide you with comments based on their experience


whell, I know that in ogre we have geometry LODs and for textures a "LOD" that makes them appear blurry & low res from certain distance making the world run smoother.


Material LODS are to provide with different rendering methods based on the objects distance from the camera, i.e using shaders when closer and a simple texture when far


whats the name of this texture "LOD" technique?


The technique that makes the texture blurry at the distance is called "Mipmapping", but its a display technique (to improve the display resolution based on the texture display size), its not a LOD technique


Does this texture "LOD" make unnecesary the creation of low res textures in photoshop as I´ve been doing till now for maping the first level of my geometry LODs?.


Mipmapping can be created automatically at image load time or can be created by the user (for better control) and inserted in the image file (dtx formats)


Can this "LOD" be controlled so that certain textures as the facades stay hi-res longer(farther) than others?


There is a mipmap bias value but its a global texture value, its not an object value


the camera. It ran ok when no shadows where in the scene but when activating the shadows everything got slow slow.


There is no magical setup for shadows, you need to experiment with the settings, the scene, the objects, and more important know how the shadow technique works, so you can optimize your scenes

If you dont need dynamic shadows, you can use lightmaps for very good results


So I think one solution could be to make a geometry LOD and aply a material to this objets that makes them not to cast shadows. I know it is posible in ogre


Select the objects, right click, select properties, and disable "Cast Shadows"


As the shadows give very nice effects (even a simple rectangular shadow) would be interesting that buildings could keep casting shadows even if they where quite far, so I think a couple of things could be done.


If you use shaders for the shadow system you can create custom setups


if the objetc placed on the sidewalk is a simple plane, as could be a plane with a texture of a horizontal road sign, there will be a problem-->the engine will ask himself wich objet must be rendered.
Till now I´ve solutioned this easylly just by elevating the objet slightly from the pavement, but this technique make this element fail or not to be
represented at med-high distances.
So, has Ogre a render priority? or something similar so that I can asign to the objets properties as "level 0" for the sidewalk and "level 1" for the
plane-object.


The materials have a "bias factor" for this kind of issues
Ogre do have render queues


I´ve more but I thinks they are enough for a single post


More than enough for a single post, you will get more answers if you present a single, very descritive question

You need to read the documentation, the material manual, and do tests, see the demos that comes with the sdk