Hello all,

I have code that needs to render regions of my object differently depending on their location. I am trying to use a colour map to define these regions, then get a value (0-14) representing this region by sampling the texture.

The problem is when I sample from my colour map, I get collisions. Ie, two regions with different colours in the colourmap get the same value returned from the sampler.

I've tried various formats of my colour map. I set the colours for each region to be "5" apart in each case;

• Indexed colour
• RGB, RGBA: region 1 will have RGB 5,5,5. region 2 will have RGB 10,10,10 and so on.
• HSV Greyscale: region 1 will have HSV 0,0,5. region 2 will have HSV 0,0,10 and so on.

The tex2D sampler returns a value [0..1]. To get the "region number" I multiply this by 100 and divide by 5, expecting a number [0..20]. (But currently only using 0-14)

I am using Shader Model 2 and FX Composer.

//Colour map
texture gColourmapTexture <
    string ResourceName = "Globe_Colourmap_Regions_Greyscale.png";
    string ResourceType = "2D";
>;
sampler2D gColourmapSampler : register(s1) = sampler_state {
Texture = <gColourmapTexture>;
#if DIRECT3D_VERSION >= 0xa00
    Filter = MIN_MAG_MIP_LINEAR;
#else /* DIRECT3D_VERSION < 0xa00 */
    MinFilter = Linear;
    MipFilter = Linear;
    MagFilter = Linear;
#endif /* DIRECT3D_VERSION */
    AddressU = Clamp; 
    AddressV = Clamp;
};

...
//Then later, in a method
float region = tex2D(gColourmapSampler,In.UV).x;
//at this point I do not think it matters which of xyz components I pick; even in HSV they're all the same for my image. 

region *= 100;  //Now in range [0..100]
region /= 5;    //Now in range [0..20]

float3 levels[21];

//*Code populating "levels" array with what is essentially colour information *
levels[1] = ...
levels[2] = ...

//Chose which level this region has, by looking up its region number
float3 Level = levels[region];