Texture sample not returning colors on the edges

Development Rendering
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1

I am trying to use a texture as a lookup for opacity for use in a material.
Basically I take a text object, gray scale texture that represent the values I want, and use Texture Sample to lookup a value by UV (Between 0.0 and 1.0)

For the purposes here I output the value as debug. The blueprint material I m using looks like this

135867-uvlookup.png
135867-uvlookup.png1221×389 115 KB

So for a UV value of zero I get 0.50, when the gradiant I am using should give me a 0.0 at the far left
Some other samples are

0.0 -> 0.5 //unexpected  
0.1 -> 0.0  
0.2 -> 0.03  
0.3 -> 0.07  
0.4 -> 0.12  
0.5 -> 0.21  
0.6 -> 0.32  
0.7 -> 0.44  
0.8 -> 0.60  
0.9 -> 0.80  
1.0 -> 0.50 //unexpected  
 
0.01 -> 0.00  
0.001 -> 0.24 //unexpected  
0.09 -> 0.99   
0.999 -> 0.75 //unexpected

Is there a better way to sample a texture by index? Why doesnt this work?

2

When using a texture as a lookup you need to modify the Texture sample Sampler Source to use Clamp, otherwise the neigne does automatic blending of the start and finish of the texture to allow it to wrap smoothly as visual. When its data CLAMP.

137993-clamp.png