Re: [Plib-users] How to determine surface material by ssgState texture filena me ?

[Steve B. <sjb...@ai...>]

McEvoy, Nick wrote:
> What is the best way to determine what type of 'surface' is under my players feet ?
> 
> My setup is follows:
> - I load a terrain (an AC3D model) with different textures, eg. grass, rock, ice.
> - I get the hits:   iNumHits = ssgIsect(reGetWorld(), &Sphere, InvMat, pHits)
> - I get the SimpleState of the hit leaf, eg.
> 
> ssgHit* h = &pHits[i];
> ssgState* pState = h->leaf->getState();
> if (pState->isA(ssgTypeSimpleState()))
> {
> 	char* sTexture = ((ssgSimpleState*)pState)->getTextureFilename();
> 
> 	// then depending on texture filename set different surface properties
> 	// - this would be a bunch of strcmp() ... too slow !!!
> }
> 
> But doing a bunch of string compares on the texture filename is going to be slow ... is it not !?
> 
> Is there a better way to do this ?

There is a user-settable integer field in the ssgState:

   void ssgState::setExternalPropertyIndex(int i)
   int  ssgState::getExternalPropertyIndex()

...you can use that to index into an array of external properties that 
you maintain.  In my games, I store properties like friction, 
bounciness, etc in a structure and make a ulList of those.

> Note: I had a quick look at the way TuxKart does it ... with a Material structure (ie. ssgState) ... but I don't quite follow how to apply these states when reading the AC3D model.
> 
> I have the vague idea that I should load the AC3D model using ssgLoaderOptions ... to handle ssgState ... and as each texture is read create my own ssgState (which I can then get in the hit leaf) ... but I'm still trying to work out how the loader options are supposed to work ... or am I barking up the wrong tree here.

The loader options allow you to have the file loader call your code 
whenever it wants to create a new ssgState - to give you the 
possibility to create your own ssgState instead of the loader doing
it for you.

That's one way to set the External Property Index - I also use it to
add features to the ssgState that the loader can't.  For example, AC3D
doesn't support non-repeating textures - so I look up the texture 
filename in my master materials table and set the 'wrap' flags myself.

This entire process is poorly documented right now - I kinda had the
idea that one day I'd wrap up a material file parser along with all
of this mechanism into an ssgAux thingy - but I havn't gotten around
to doing that yet.

---------------------------- Steve Baker -------------------------
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