Cycles - Driver Node?

There are certain nodes within cycles that dont have inputs for some values.

For example on the colour ramp node - the position input box for a particular colour tag on the colour ramp.

You can however right click this and add a driver so that this value can be animated.

My question is - is there any way this driver can be linked to a cycles node (e.g. a value input node) so that it can be exposed to a node group input?

For animations it works, because the value only changes between frames. But as something you can put in a socket, it won’t work. Those variables stay constant in the nodetree during the whole frame render.

Yep - I don’t want the value to change - I just want to expose it to group input slots. It’s easier to change the value of a group input value - than to have to open up the node tree and modify the value in the colour ramp itself.

Then it’s possible with python nodes. :cool:
It won’t be a socket, but you can draw the interface of some node on the outside of the nodetree (for example, with the color ramp template)

I’ll have to have a read up on Python then :smiley:

i’m testing it now… unfortunatly changes to the color ramp through the interface are not updated automatically…

here what I have so far (you’ll need my addon for this):

  • make the nodegroup with the color ramp inside

  • with the nodegroup selected (not opened), press ‘SPACE’ and look for ‘Convert Nodegroup to PyNode’

  • give it a bl_name and a bl_label and press OK.

  • In the text editor, edit the scripted node (it’s in the addons folder, ‘\ShaderNodesExtra\Nodes’), change the line:

    #def draw_buttons(self, context, layout):


    def draw_buttons(self, context, layout):
        layout.template_color_ramp(self.node_tree.nodes[name of the colorramp node], 'color_ramp')
  • save the file, restart blender, and it should be working (look in the ‘custom nodes’ on add menu)

For updating, you can put ‘context.space_data.edit_tree.update_tag()’ above the ‘layout.template_color_ramp(…)’ line. It’s not the best approach but it works.