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 A bug in Wiki-LWJGL tutorial?  (Read 3948 times) 0 Members and 1 Guest are viewing this topic.
preshel

Senior Newbie

 « Posted 2007-02-26 22:52:16 »

Hi,

I've checked out the speedy VBO in
http://lwjgl.org/wiki/doku.php/lwjgl/tutorials/opengl/speedyvbo#interleaving_a_vbo

and I've notived that:

 1  2 `// texture coordinates offset = (3 + 3 + 2) * 4;GL11.glTexCoordPointer(2, GL_FLOAT, stride, offset);`

Looks a little bit strange... shouldn't it be offset = (3 + 3 + 4) * 4 instead?

Anyway, i've solved my bug problems... it was all due to an unupdated driver of my laptop, and apperantly, now i DO have VBO supported... yey!
darkprophet

Senior Devvie

 « Reply #1 - Posted 2007-02-26 23:49:11 »

I wrote that tutorial, im glad it helped.

Lets regard each "component" as a unit. So the x component of the vertex is 1 unit. That means each vertex has 3 units, each normal has 3 units and 2d texture coordinates have 2 units (remember its just ST coordinates). Thats the reason behind the 3 + 3 + 2 offset. The * 4 is to change that to be in terms of bytes.

DP

Friends don't let friends make MMORPGs.

Blog | Volatile-Engine
preshel

Senior Newbie

 « Reply #2 - Posted 2007-02-27 11:03:05 »

yes, i understand what the x4 means, but if u decided that the interleaved structure is like this:
V[xyz]N[xyz]C[rgba]T1[st]

then the offset for the starting of the texture should be (3+3+4)*4 and not (3+3+2)*4, since the color have rgba channels = 4 channel..., and it comes before the texture channels...

btw - i already implemented it, and its 3+3+4.
please check ur tutorial again (it really helped me, though !).
darkprophet

Senior Devvie

 « Reply #3 - Posted 2007-02-27 11:51:43 »

no, since the offset for vertices is 0 not 3

And Ive implemented the 3+3+2 successfully in a game engine a very long while back

DP

Friends don't let friends make MMORPGs.

Blog | Volatile-Engine
preshel

Senior Newbie

 « Reply #4 - Posted 2007-03-01 11:20:05 »

sorry, but i insist

the structure should be
V[3*4byte]N[3*4byte]C[4*4byte]T1[2*byte]

so if i need the texture (s,t) , i need to do :
 1  2 `intlvdarr[4*(3+3+4)+0] = texture_s;intlvdarr[4*(3+3+4)+1] = texture_t;`

the texture offset WOULD be 3+3+2 for the following structure:
V[3*4byte]N[3*4byte]T1[2*byte]C[4*4byte]

preshel

Senior Newbie

 « Reply #5 - Posted 2007-03-01 11:20:59 »

sorry, it would be 4*(3+3).

in any case it should not be (3+3+2) ....
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