Filtering Texture Maps In Vex

[B.Walters]

No matter how extreme I set the values to, my image doesn't seem to blur. Neither am I seemingly able to change the filter method ("box", "point", etc), so I assume something is wrong with my code despite the fact that I don't get any errors and the shader successfully renders with a texture map:

Cf= texture(texmap, uv.x, uv.y, "filter", filter, "width", width);

Another related question: if I only wanted a specific channel (say the alpha channel), how would I access that?

[stevenong]

Hi,

You have to convert your image to .rat format for filtering to work.

I don't know the exact answer to your second question off the top of my head but you want to use a vector4 to represent RGBA then convert it to a vector3 (RGB) and a float(A).

Hope the above helps!

Cheers!

steven

[B.Walters]

Absolutely, thanks steven!

And if anybody knows of a more efficient way to get a specific channel from an image, please let me know as I'm still looking.

[Mario Marengo]

And if anybody knows of a more efficient way to get a specific channel from an image, please let me know as I'm still looking.

I don't know about more efficient, but, AFAIK, in VEX (and in H8), you can access the individual members of a compound type (like vector and vector4) with the "dot" operator. The predefined names for the four members of a vector4 type are {x,y,z,w} or {r,g,b,a}, so something like this should be possible:

// fetch the RGBA texture color
vector4 tx  = texture(...);

// or with an explicit cast, though it shouldn't be necessary 
// in a simple assignment:
// vector4 tx  = vector4(texture(...));

// then do stuff with the elements
vector  RGB = set(tx.r,tx.g,tx.b);
float   R   = tx.r;
float   G   = tx.g;
float   B   = tx.b;
float   A   = tx.a;

(untested...)

[stevenong]

Please use Mario's suggestion as he knows what he's talking about.

Cheers!

steven

[Mario Marengo]

Please use Mario's suggestion as he knows what he's talking about.

Thanks, but so do you!

...however, in all cases, I recommend we all give the last word to crunch's "little bird"...

[stu]

...however, in all cases, I recommend we all give the last word to crunch's "little bird"...

Too easy.