plib-devel

RE: [Plib-devel] texture support for ssgLoadOBJ

[Dave M. <Dav...@dy...>]

> >I added texture support to the Wavefront OBJ loader.

Wolfram wrote:
> I tried it on some files of my own, but due to lots of problems,
> (most ?) unrelated to the *.obj-loader didnt succeed (yet).
send me any OBJ files that don't work

> - I had a texture with a size that is not a power of two.
> plib complained (map is not a power-of-two in size)
> and exits the program!
i'll track that down if you want to send me the texture

--
Dave McClurg

RE: [Plib-devel] texture support for ssgLoadOBJ

[Dave M. <Dav...@dy...>]

> >> - I had a texture with a size that is not a power of two.
> >> plib complained (map is not a power-of-two in size)
> >> and exits the program!
> 
> - Dont load wrong textures, give an error-message, go on loading
> everything else.
>
done.  i used Steve's loadDummyTexture() in the event that
make_mip_maps() finds non power-of-two sizes.

while i was at it, i added some simple error message routines:

	void ssgSetError(const char *fmt, ...);
	char* ssgGetError(void);
	void ssgClearError(void);

this is similar to what SDL uses.  SetError fprintfs to stderr
and stores the message in a buffer that can be retreived with
GetError.  SetError could also echo to a stderr.txt file if
we want to capture multiple error messages.

I'd like to apply these error message routines to my loaders
and perhaps all of SSG unless there are objections.

-- Dave McClurg

Re: [Plib-devel] texture support for ssgLoadOBJ

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

> Dave McClurg wrote:

> while i was at it, i added some simple error message routines:
> 
>         void ssgSetError(const char *fmt, ...);
>         char* ssgGetError(void);
>         void ssgClearError(void);

There should probably be a 'severity' indicator:

   SSG_DEBUG   -- Messages that can safely be ignored.
   SSG_WARNING -- Messages that are important.
   SSG_FATAL   -- Errors that SSG cannot recover from.

It would be nice for the application to be able to register
a callback that SSG will call when an error occours - have
it default to something that just dumps the message to stderr.

> I'd like to apply these error message routines to my loaders
> and perhaps all of SSG unless there are objections.

Nope no objections - we need something along these lines.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

Re: [Plib-devel] texture support for ssgLoadOBJ

[Wolfram K. <w_...@rz...>]

Dave wrote:

>
>> - I had a texture with a size that is not a power of two.
>> plib complained (map is not a power-of-two in size)
>> and exits the program!
>i'll track that down if you want to send me the texture

Lets first decide what we want :-).
I think most or all graphics cards want to have texture-sizes
that are a power of two. So, internally, we should only have such
textures.
I see two ways to deal with this:
- Dont load wrong textures, give an error-message, go on loading
everything else.
- Resample the texture when loading. This, of course, slows loading
the texture. Therefore, authors (of games or whatever) should resample
their textures once in a paint-program anyway. If we go this way,
I want a dialog saying "this is not a nice texture, if you want to go
on using it or even distribute it, resample it".
It is surprising how uniformed people can be, even if they create
textures professionally. For a long time, we had monochrome textures
with a size of, for example 118x112 pixels :-(.
So, our program was used with the hand brake on :-(. (German idiom,
translated into English. I dont know whether there is an English one).

Bye bye,
Wolfram Kuss.

[Plib-devel] ssg error message routines

[Dave M. <dp...@ef...>]

more info on the error routines I added:

	void ssgSetError ( const char* fmt, ... ) ;
	char* ssgGetError ( void ) ;
	void ssgClearError ( void ) ;

Here are some examples of how an application might
handle errors.  If ErrorBox() shows a message to the
user then to handle a fatal load error:

	ent = ssgLoad ( fname ) ;
	if ( ent == NULL ) {
	   ErrorBox ( ssgGetError() ) ;
	}

To handle all load error returns:

	ssgClearError();
	ent = ssgLoad ( fname ) ;
	if ( ent == NULL ) {
	   //fatal error
	   ErrorBox ( ssgGetError() ) ;
	}
	else if ( strcmp(ssgGetError(), "") != 0 ) {
	   //non-fatal errors ... still returned something
	   ErrorBox ( ssgGetError() ) ;
      }

PPE should probably do something like this.

This is how it is done in SDL (Simple Direct Media Layer)
and I would like to do it the same in SSG
unless there are objections.

To handle multiple error messages, the application
could redirect stderr to a file or I could echo errors
to a file in ssgSetError().  which do you prefer?

-- Dave McClurg

Re: [Plib-devel] ssg error message routines

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

Dave McClurg wrote:

> PPE should probably do something like this.

...so I guess it shouldn't be an SSG function - but
something general to all of PLIB - including PUI, SL,
etc.  As a general library, the application might like
to handle it's own errors the same way.

> To handle multiple error messages, the application
> could redirect stderr to a file or I could echo errors
> to a file in ssgSetError().  which do you prefer?

Using a callback into the application would solve the
problem of multiple errors.
 
(That's how Performer handles it).

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

Re: [Plib-devel] texture support for ssgLoadOBJ

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

Wolfram Kuss wrote:
> 
> Dave wrote:
> 
> >
> >> - I had a texture with a size that is not a power of two.
> >> plib complained (map is not a power-of-two in size)
> >> and exits the program!
> >i'll track that down if you want to send me the texture
> 
> Lets first decide what we want :-).
> I think most or all graphics cards want to have texture-sizes
> that are a power of two. So, internally, we should only have such
> textures.

More than that - it is a REQUIREMENT of OpenGL that maps have
power of two sizes.

Before we started to use SSG for PPE and stuff like that, it didn't
matter that it exited when something as serious as this happened.
The developer of a game would see his error and fix it.  No big
deal.

However, now that SSG is used in things like the PPE modeller, it's
important that we can survive without crashing - and yet still report
the seriousness of the problem to the application.

> I see two ways to deal with this:
> - Dont load wrong textures, give an error-message, go on loading
> everything else.

Exactly.

> - Resample the texture when loading. This, of course, slows loading
> the texture. Therefore, authors (of games or whatever) should resample
> their textures once in a paint-program anyway. If we go this way,
> I want a dialog saying "this is not a nice texture, if you want to go
> on using it or even distribute it, resample it".

I don't think that's a good plan.  People will ignore the error if SSG
kludges a fix - and the texture will just look bad.

Replace the broken texture with a magenta and green chequerboard or
something.  People learn to recognise this as the 'broken texture'
symptom.

> It is surprising how uniformed people can be, even if they create
> textures professionally. For a long time, we had monochrome textures
> with a size of, for example 118x112 pixels :-(.
> So, our program was used with the hand brake on :-(. (German idiom,
> translated into English. I dont know whether there is an English one).

Yep.  OpenGL implementations are SUPPOSED to ignore non-power of two
maps...not all of them do.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)