Hi! I'm learning to use Houdini and am trying to use a ramp node in an attribute VOP subnetwork to colour some particles, but it doesn't behave in the way I expected it to.

Can anyone please explain how to use the Ramp Parameter node / its limitations? Perhaps it can't be used for arbitrary float values and only works with specific nodes before/after it.

The documentation explains "the Ramp Parameter node represents a ramp user interface. The input specifies an index into the ramp. The value of the ramp at that position is the node’s output"

My expectation is that if a node with an output of 0.5f is wired into the Ramp Parameter node's input, the output will be the value of the ramp at position 0.5 (half way along the curve in the parameter interface).

In this case, I am placing the Ramp node in-between vec to float / float to vec nodes on the 'red' channel (first input), with the ramp set to a value of 1 at position 0 and a value of 1 at position 1 - i.e., any input between 0 and 1 should result in an output of 1. Therefore, I expected the red channel to always be 1 (only see reds/oranges/yellows), but instead the red channel is always 0 (only see blues/greens).

I tried creating a minimum working example to demonstrate where I also placed a "Ramps" node before the float to vec to ensure the input was always in the range 0-1.





Any help would be much appreciated!

Thanks,
Joe