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AppGameKit Classic Chat / AGK obj parser

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Matty H
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Posted: 19th Jan 2013 12:53
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I noticed that the 3D level provided with AppGameKit has four values for each vertex texture coordinate:



The obj I am trying to load has three, and the third is always 0. This model does not have correct uv coordinates when loaded into AGK. I may be able to write something to convert it for use in AppGameKit but I need to understand what the four values are for.

Is AppGameKit supposed to be able to handle vt with 2 or 3 values? If so then perhaps something else is wrong with my obj file?

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baxslash
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Posted: 20th Jan 2013 00:47
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Normally a obj file uses 2 values for vt, they are U and V co-ordinates. There is an optional W value which normally corresponds to weight but since there are two extra values I would guess these are UV values for the light map. I'd have to check with Lee to be sure but that's my guess Matty. I have been experimenting a little with creating my own obj files too for a personal project I started over Christmas.


this.mess = abs(sin(times#))
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MikeMax
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Posted: 20th Jan 2013 01:30
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Yes it would make sense Not a standard OBJ structure but ingenious
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Matty H
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Posted: 20th Jan 2013 14:35
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Thanks for the response, just after I posted I realised that it will be two sets of uv coordinates, which is a handy option.

But one set should be accepted also, otherwise the format is not too useful for standard obj files.

I think if I add another 0 to my obj files uv data they may parse correctly?

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baxslash
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Posted: 20th Jan 2013 18:21
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Yes, I think zero is the default.


this.mess = abs(sin(times#))
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Paul Johnston
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Posted: 22nd Jan 2013 01:30
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The standard OBJ spec allows up to three UVW values as baxslash says. If AppGameKit finds three values it reads the first two (UV) and ignores the last (W). We made a special case that if it has four values then we read the first two as normal, but then read the second two as a second set of UV coordinates, in this case they were for a light map.
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Matty H
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Posted: 5th Mar 2013 00:04
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I think I found the problem. It seems the uv coordinates can't be above 1.0?

I could be wrong since I am not a modeller so perhaps the mistake is on my part. Anyway, using milkshape I can set the uv coordinates outside the range of 0.0 -> 1.0 and it works, it also shows up correct in other model viewers but AppGameKit has a problem and the texture looks all stretched.

Is this a bug, or is it just agk is using a different texture mode, if so, can we change it? Perhaps using our own shaders?

Thanks.

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MikeMax
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Posted: 5th Mar 2013 01:56
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Over 1.0 is texture repeats. You have to normalize to 1.0

For example : 1.5 will be 0.5.

Simply mod you uv values like this only if greater than 1.0) :

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