Hi there

I am facing some really confusing questions regarding
collisions.Here are my queries :-

1) . How is the collision betweeen 2 mdl entities performed
i.e what type,shape,size of a bouding box is used ?

2). How is the collision between a "Trace" ray and a mdl
entity performed i.e what shape and size of mdl is used ?

3).How will the above collision detection be affected if I scale
the model up and down ?

4).How is the collision between a map entity and a model entity
performed ?

5).Suppose I have a huge glass window and I want it to break when
I use a gun which uses a "trace" or "shoot" ray as the bullet,then
will the trace ray detect both map and mdl entities equally well ?
I think its written in the manual that mdl entities use a fixed size
bounding box and so the edges of the window won't be detected.

6).Another problem that I am facing is that I use a map entity as
a door.I have written the code such that when the door is closing
and it collides against the player model,then the door stops closing
and goes back.But the problem I'm facing is that whenever the door
is closing and even if I am some distance away from the door,the door
stops closing and goes back.Is it because of some hull based collision
that is preventing the door from closing.

I would be really happy if somebody can throw light on my querries
as I'm completely stalled.Any help will be greatly appreciated.

zazang

Doug,JCL ?..please answer as this is of
utmost importance to me right now and I'm
unable to proceed with my work...

Doug,JCL,Marco...pls answer for I am loosing
faith in A5...

Doug, we would be pleased to have an answer on the questions below.

Thank you in advance.

i think doug or jcl won't answer questions you can answer with "read the manual".
do this and try out how collision will work.

I didn't find the manual good enough and collision detection has been written so breifly.I think it needs a much better
explanation.

yep, the explanation of collision-detection is pretty bad.
By the way: your door, is it swinging or moved by the move-instruction?

Actually most of this is pretty well-explained in the manual (no offence meant):

1) "...the bounding boxes of the two entities are tested against each other." Shape: er, box-shaped. Size: see max_x, min_x etc. The box is determined by the size of your model (I think it's taken from the first frame, but I'm not sure.) You can change the size using the min_x, max_x commands...

2) See trace() in the manual. You can set use_box in trace_mode to determine whether it detects the hull or the bounding box. Either way, the trace actually hits the box (bounding box or hull) of the model, and NOT the MDL itself, so if you are emitting blood or suchlike you need to detect the nearest vertex, otherwise the blood may seem to be emitted from nearby the model...
3) The bounding box is determined by the model, so as you can only scale the models before you save them to MDL, this won't have any effect - ie the box will be as big as your model.

4) "The hull is used for collisions of a moving entity against the level or map entities. This (sic) kind of collisions detect each polygon of the target entity." Pretty straightforward...

5) Not sure I understand the question, but seeing as either way the window would be square, it should make no difference - it should be detected just as well whatever type of collision you used.

6) Could be your trigger range. Is the door set to open automatically?

Hope that's of some help, don't mean to be too RTFM on you,
Cheers,
Keith

Hi Keith

Thanks for the good pointers.No offences taken..

zazang

Ambit:

Regarding point #4 of your explaination. Maybe you can explain something for me.

I have a level with some mountains that I added. These mountains were made by using the Primitive 'cube'. My entity is a mdl helicopter. It's movements are controlled by the move instruction, which I understand uses collision detection. Well, everything works great until I try to move sideways (or use straf mode). Then my chopper goes right thru the mountains, when actually my entity should stop or be blocked.

Can u explain why this happens?

thx