plib-users

[Plib-users] Texture scaling

[Erik U. <un...@et...>]

Hello,

I would like to change the scaling of a texture on an object.
What would be the easiest way to do that?


Best regards,

Erik

-------------------------------------------
Erik Unemyr
E-mail: un...@et...

Student @ Chalmers University of Technology
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Re: [Plib-users] Texture scaling

[<le...@ci...>]

Quoting Erik Unemyr <un...@et...>:

> Hello,
> 
> I would like to change the scaling of a texture on an object.
> What would be the easiest way to do that?

Official SSG approach: put your object under (kid of) a ssgTextureTransform 
node, where you can issue the transformation you need to apply to the texture.

My preferred: set an object's pre-draw callback which apply the texture matrix:

glmatrixmode GL_TEXTURE;
glloadmatrix <your matrix> or glscale ...;
return 1;

and a post-draw callback to reset the texture matrix:

glmatrixmode GL_TEXTURE;
glloadidentitymatrix;
return 1;

I like the latter since you don't need to rearrange your scene graph, just need 
object's node pointer. So I use it for leaf objects (meshes).

Sorry for the pseudoGLcode, I can never remember exactly the call syntax when 
I'm far from my sources.

> Best regards,
> 
> Erik

Greetings -

Paolo 

-------------------------------------------
Paolo Leoncini
E-mail: p.l...@ci...
-------------------------------------------

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Re: [Plib-users] Texture scaling

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

Erik Unemyr wrote:
> Hello,
> 
> I would like to change the scaling of a texture on an object.
> What would be the easiest way to do that?
You could push/pop the texture transform matrix in the SSG draw
callback.

It's usually just easier to multiply the texture coordinates yourself,
unless there are truly VAST numbers of vertices that have to be
continually re-scaled, it's generally not worth the overhead to
do it with the texture matrix.

---------------------------- Steve Baker -------------------------
HomeEmail: <sjb...@ai...>    WorkEmail: <sj...@li...>
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