"Wonky" model geometry collision.

[meshcarver 12]

Hey up,

I'm modelling some oil drums for the STALKER island I'm doing, and have made them slightly wonky.

Does this mean I might aswell dulpicate this base mesh for the geometry collision LOD, as it's not all 90 degrees striaght lines etc.

Also for the fire LOD, is it ok to duplicate them mesh aswell, so it's nice and tight bullet hits etc..?

Also, I've given the oil drum a 1024x1024 texture.

Is this too much do you think..? I wanted some hi-res to it, as hopefully there'll be many a STALKER spending the night huddled close to it lol...

Cheers guys.

Btw, I'm sort of new to this forum stuff too, so if I want to upload an image to show you, how do I go about it please, as it asks me for a URL..?

Marc

Edited September 8, 2012 by meanmachine1

[max power 21]

Some pics would be handy.

[PuFu 4600]

Hey up,

I'm modelling some oil drums for the STALKER island I'm doing, and have made them slightly wonky.

Does this mean I might aswell dulpicate this base mesh for the geometry collision LOD, as it's not all 90 degrees striaght lines etc.

Also for the fire LOD, is it ok to duplicate them mesh aswell, so it's nice and tight bullet hits etc..?

Also, I've given the oil drum a 1024x1024 texture.

Is this too much do you think..? I wanted some hi-res to it, as hopefully there'll be many a STALKER spending the night huddled close to it lol...

Cheers guys.

Btw, I'm sort of new to this forum stuff too, so if I want to upload an image to show you, how do I go about it please, as it asks me for a URL..?

Marc

you don't upload files on this forum, bur rather to external pic websites (like fliker, picasa, imgur, imageshack <- hate this one) and use the link here

Some pics would be handy.

+1

i have no fucking clue what you are talking about marc.

[meshcarver 12]

Here's a picture,

basically as I've made the oildrum battered and wonky, does this mean the geo/fire/shadow lod etc have to match it curve for curve? Like in "A" and "B"..?

Or can I use a simpler geo/fire/shadow lod like "C"..?

cheers guys.

http://www.flickr.com/photos/86890612@N02/7956882130/in/photostream

[max power 21]

Okay, we need to review the meaning of the word 'convex'.

A and B are not convex. There have been several threads recently where we discussed the need for convex hulls in detail. Please search before posting.

All of those meshes are waaay more complex than you need. While your artwork is impressive, having a barrel with so much detail in its collision model is a waste of resources. I read somewhere that the collision geometry has issues with volumes less than 1 meter thick. While I don't find that to be true in my experience, having a vertex every six inches is definitely much more than you need. Defining the lid on the oil drum is definitely not required, as it will never influence any collision at any time.

Regarding the design of your oil drum full of burnt wood: remember that if the thing is knocked over, it will roll around... so the wood and ashed will stay static like they are set in concrete. In my experience as well, things with pointy GeoLODs tend to buck up and dance around. If your barrel is knocked over onto the wood parts sticking out, it will probably dance and bounce around.

It's all well and good to have a nice, tight collision model, but the physics engine is not nice or tight. I would consider making a 12 sided cylinder at most for your collision geometry and leave it at that.

And again, all components of the geolod must be convex hulls.

[meshcarver 12]

Hi Max,

aye man, I should've already mentioned I do understand (And have encountered and corrected) the concave problem. This isn't a thread about convex/concave. I duplicated these res lods to get my point across to you quickly.

I agree for things like the lid/wood/little "edges" around the barrel body there's no point having them in the other types of LODS.

As a compromise to details, would a 20 sided cylinder do it, to match the curve of the barrel itself?

I guess I was trying to work out if its not a VERY accurate geo/fire lod, then the bullets will fly thru some parts of visible mesh- I encountered this recently firing thru those dragons teeth roadblock things. Bullets were hitting fresh air next to them and sparking.

Also, I could make it so it's pretty massed up, so is very difficult to knock over? Is that possible?

Again man, thanks for your help.

Edited on: a 12/20 sided for the geolod, but would it be worth it to include basic blocks for the wooden pieces into the firelod?

Edited September 8, 2012 by meanmachine1

[PuFu 4600]

Edited on: a 12/20 sided for the geolod, but would it be worth it to include basic blocks for the wooden pieces into the firelod?

make it 12 sided. it can be a bit larger as long as it is the same radius and envelops the geometry.

basic blocks as a simple 6 face boxes would be enough. and yes it is worth it if you don't want to be able to fire through the wooden pieces. i would put only the 2 out of 3 thicker ones in, leaving the smaller one out.

[meshcarver 12]

cheers man... I'll bear that in mind for next time.

[max power 21]

The firegeolod can be slightly more complex, but to give the illusion that you're shooting something it needs not follow the form of the shape you're representing completely. The particles will still show up fairly well properly if the face is inside / outside of the res lod a little bit.

[meshcarver 12]

You've hit the nail on the head for me there Max.

Aye, I get mixed up with the "geolod and the "firelod"- basically, the geolod is for the player collision in effect yes..? Where he bumps into it etc, and if it falls over, it'll roll depending on the geolod?

Then, the firelod is what the projectiles hit..? So it sparks etc depending on firelod, hence make that one a bit more true to form to an extent..?

Thank you again man...

[max power 21]

Aye, I get mixed up with the "geolod and the "firelod"- basically, the geolod is for the player collision in effect yes..? Where he bumps into it etc, and if it falls over, it'll roll depending on the geolod?

The geolod defines the physical dimensions and mass of the object for the physics engine for the purposes of collisions.

Then, the firelod is what the projectiles hit..? So it sparks etc depending on firelod, hence make that one a bit more true to form to an extent..?

Thank you again man...

The firegeolod is indeed what projectiles hit, and you can define different ballistic behaviours per face by using penetration materials.

[Sealife 22]

Why don't you download arma 1 mlods ?

They area great tool to learn basics , there are barrels , houses ,trees, and everything you could need to learn basic requirements .

[Robster 11]

I think you don't need FireGeo LOD for that model, since it does not have any "holes" on it... If I have a wall with a window I can make a full wall for GeoLOD and let the FireGeo LOD deal with the open space where bullets will go trough... this way you save Polys also and model work just fine anyways...

In this case you can add a bisurf RVMAT in Geo LOD and that's all...

Needed RVMATs are located at p:\ca\data\penetration ... though you can make your own definitions, BIS list seems to be quite enough...

There you'll find metal and wood for your own purposes. Assign a corresponding surface definition to your model's textures and then you will start to see special bullet hits...

Here you have a shooting example over wooden stairs...

Edited September 10, 2012 by Robster

[max power 21]

I believe that the objects in the firegeoLOD can be made more gracile than those in the geolod... If you have a paper thin geolod, I think it can cause collision detection problems.

[meshcarver 12]

Thanks guys,

this is ALL very helpful for me, and any other newbies who come across this thread. :)

[Robster 11]

I believe that the objects in the firegeoLOD can be made more gracile than those in the geolod... If you have a paper thin geolod, I think it can cause collision detection problems.

Once I wanted to know how geo lods worked I began to see BI models... then I found that fire geo is used in certain models...

Regarding their specific purpose, these FireGeo LODs tend to be more detailed -gracile?- than a simple geo LOD... but both basic geo and fire geo admit surface definitions... to tell how bullets will collide on a certain object, going through or not, etc...

Afaik collision detection problems depends on size and overlapping vertex rather than geo lod type... so, whenever oxygen says any geo lod is ok, I've found it working without any problem in-game...

Whenever I have geo related issues it's been because there was something wrong inside lod, components, etc... for instance, finding a roadway bad placed over a geo lod... anyhow, when I've tried to change default model size in VIS3PE I've gotten weird results sometimes...

Bad collision detection also depends on character model itself... I guess you've seen that bumpy quad motor bike crossing bridges, custom or not, have you? lol in ArmA1 I saw MBTs turning upside down just like waffles when attempting to cross bridges hahaha

We also find some gaps regarding humal models... if you take, for example, a plain ramp BI model and put it at different heights over the ground, you'll notice how characters collides at certain heights with different results:

up to 80 cms -> character soldier collides, can't go through

between 50/40 cms aproximately -> collision detection works and human character goes inside/outside model by pressing v key... present roadway is not detected (I guess it's still too high)

about 10-30 cms above ground -> character walks over it... roadways is detected whenever it goes straight walking or by pressing v key...

(BTW why these simulated human beings do not jump by default? c'mon it's just a simple jump... I know engine doesn't need it, but that's something oftenly used in RL)

Have you noticed collision on any fence type model... ??? well, any wall that goes down then become "virtual", I mean, it won't have any Geo LOD working... just like any clutter like type of thing (clutter type models does not use any geo lods, even when model used for clutter have'em)

Have you seeing AI going trough hescos BI models??? or AI zombies going trough doors... ??? it might really piss you off when you're making an outpost into the mountains... or you can learn to deal with frequent complaints...

So, I tend to check models behaviour in-game... if bullet hitting is working properly, then one basic geo lod is good enough for me... until I find a bug or someone show me a good reason to make up my mind...

But, can you tell us about your own experience regarding collision detection issues?

Edited September 10, 2012 by Robster

[max power 21]

AI human type units do not collide with objects. They do pathfind around them, though. It is not a physics problem, but one ensuring that a unit never gets physically stuck somewhere.