**System Information**

GNULinux (fedora 22) intel cpu, nvidia gpu

**Blender Version**

Broken: (example: 2.69.7 e5e1010

Worked: ?

**Short description of error**

when Vector Curves are not linear, and we have a point at 0,0 feeding in zero doesn't give zero but some non zero output. I'm unable to predict or understand what the math going on here is supposed to be...

**Exact steps for others to reproduce the error**

- download the attached .blend{F262008}
- open it in blender
- turn on viewport rendering
- try plugging in R then G then B into the Emission Strength, you get a black cube
- the same for Y and Z, but if you plug in X you get some greyness
- plug in Y, you should get a black cube again
- now create a point in the middle of the Y curve and move it away from the linear curve
- You now get a grey cube!

what I expect is the cube to stay black since the input is zero/zero/zero and all the curves have a point at zero, zero