Re: [openvrml-develop] Viewpoint change

[cheribhai <cha...@gm...>]

I agree. I think viewpoint jumps and animations can be quite useful at times.
In my case I need to actually perform the 'bind' to another viewport, so
isBound is not good enough. 

But do you propose exposing the 'bind' method only for the viewpoint_node
(which I think should be enough, since this is probably the only bindable
node that the browser is allowed to manipulate) or are you thinking about a
more general approach?

cheers - cherian


Braden McDaniel wrote:
> 
> On Fri, 2010-03-26 at 08:48 -0700, cheribhai wrote: 
>> 
>> 
>> Hello,
>>        A couple of questions concerning change in viewpoint.
>> (1) The VRML97 spec says that 'The jump field specifies whether the
>> user's
>> view "jumps" to the position and orientation of a bound Viewpoint node or
>> remains unchanged.'
>> The way I see it, if jump is true the viewpoint user view transform
>> should
>> by set to identity, which the following code does.
>> 
>> void openvrml_node_vrml97::viewpoint_node::bind(const bool val,
>>                                                 const double timestamp)
>>     OPENVRML_THROW1(std::bad_alloc)
>> {
>>     this->is_bound_.value(val);
>>     last_user_view_transform_ = user_view_transform_;
>>     if(this->jump_.value())
>>         this->user_view_transform_ = openvrml::make_mat4f();
>>     node::emit_event(this->is_bound_emitter_, timestamp);
>> }
>> 
>> Am I right on this?
> 
> Yes, I think that looks good.
> 
> I thought I remembered getting this stuff working.  I was certainly
> thinking about it when I wrote the user_view_transform stuff; maybe I
> just didn't quite finish the idea.
> 
>> (2) I am trying to implement viewpoint change animation in a custom
>> browser.
>> For this it seems that I need the attribute value of
>> viewpoint_metatype::bind function  to be set to visible (OPENVRML_API). 
>> 
>> Is this the way to go about what I want to do or is there another way
>> around
>> this?
> 
> Well, it's not going to be that simple.  viewpoint_metatype lives in a
> dynamically loaded module; it's not something you'd link against.
> 
> Is openvrml_node_vrml97::viewpoint_node::is_bound_ what you really want?
> Of course, openvrml_node_vrml97::viewpoint_node lives in the same
> dynamically loaded module; but in this case, it's not to hard to expose
> functionality by pushing it up to the openvrml::viewpoint_node
> interface.
> 
> There was a time that I was trying to avoid committing the libopenvrml
> interface to the bindable node stack concepts; I was hoping that X3D
> would evolve away from that brain damage.  But it didn't.  So there's a
> compelling argument to be made that there's no point in continuing to
> run from this.
> 
> -- 
> Braden McDaniel <br...@en...>
> 
> 
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