How to make a sampler2D struct with dynamic values? - hlsl

Question

Here's my scenario:
texture diffuseMap;
sampler2D diffuseSampler = sampler_state {
Texture = <diffuseMap>;
Filter = MIN_MAG_MIP_LINEAR;
AddressU = WRAP;
AddressV = WRAP;
};
I would like to be able to change the diffuseSampler Filter value from within my C# application by passing a parameter to my effect. Here is how I pictured it:
#define __DiffuseFilterLinear 0x0
#define __DiffuseFilterAnisotropic 0x1
#define __DiffuseFilterNearest 0x2
int diffuseMapFilter; // Here's where I'll assign, via my application,
// a hex value corresponding to one of the three
// #defines above
Then, inside diffuseSampler, I would like to achieve the equivalent to setting the Filter value using conditionals, like so:
sampler2D diffuseSampler = sampler_state {
Texture = <diffuseMap>;
// Conditionals to pick the right Filter value
switch (diffuseMapFilter)
{
case __DiffuseFilterLinear:
Filter = MIN_MAG_MIP_LINEAR;
break;
case __DiffuseFilterAnisotropic:
Filter = ANISOTROPIC;
break;
case __DiffuseFilterNearest:
Filter = MIN_MAG_MIP_POINT;
break;
}
AddressU = WRAP;
AddressV = WRAP;
};
I know trying to insert a switch block inside a sampler struct is probably an heresy, but I think it illustrates what I am trying to do.
How can I set the diffuseSampler Filter value according to the diffuseMapFilter parameter?

Answer 1

A shader is consist of vertex shader and pixel shader. The stream of 3D model flows from application to the vertex shader, then to the pixel shader, finally to the frame buffer. a2v struct represents the data structure transferred from an application to a vertex shader, v2p from a vertex shader to a pixel shader, and p2f from a pixel shader to the frame buffer. Below program transforms a vertex's position into the position of clip space by view matrix.
struct a2v {
float4 Position : POSITION;
};
Inside the HLSL function, struct a2v specifies a vertex structure that represents the data of a vertice.
struct v2p {
float4 Position : POSITION;
};
struct v2p specifies a stream structure from vertex to pixel shader. Position is a four dimentional vector declared by float4. Furthermore, POSITION, called output semantic, indicates the initialized type of Position.
void main(in a2v IN, out v2p OUT, uniform float4x4 ModelViewMatrix)
{
OUT.Position = mul(IN.Position, ModelViewMatrix);
}
Here's a tutorial