well, it depends on the actual shader that you are sending it to of course... and whether it is a vector4 or a vector3 or whatever type...
Basically a vector can be thought of as a data structure that contains sets of numbers... 3 in the case of a vector3 and 4 nithe case of a vector 4....
They are usually named - x, y, z, w -- with "w" being the 4th in a vector4.
They are generally used to set variables inside shaders that represent angles that something is looking at or pointing at, or where something is positioned, aswell as things like texture co-ordinates...
For example, in one of the Advanced Terrain shaders that I use(it was written by Green Gandalf btw) there is an effect constant called "lightDir" which tells the shader which direction the light is coming from on the terrain, you set that constant with the call to dbSetEffectConstantVector .. passing it a vector..
you might make a vector like so :
int iNull = dbMakeVector4(1);
then you would set it's values :
dbSetVector4(1, 1.0, 1.0, 1.0, 1.0); - notice the first integer value is the "ID" of the vector(in GDK 3D maths objects like vectors and matrices have ID's like 3d objects do), the following 4 paramerters represent the x, y, z and w values.
once the vector is set, it is passed to a function like so :
dbSetEffectConstantVector(1, "lightDir", 1); the parameters for that command are :
the first integer is the ID of the effect
the second character array is the contant name within the shader
the third and last parameter is the ID of the vector you are sending to the shader.
It is not only Vectors that are used with shaders though, we can also send them Matrix values from a matrix object with :
dbSetEffectConstantMatrix(); it has similar syntax to the vector one, it just takes a matrix object instead, however, matrices in shaders are generally used for things like projection matrix calculations and things...
Hope this answers your question, im pretty new to shaders myself so i may be off on some of the info.
If it ain't broke.... DONT FIX IT !!!
