PDA

View Full Version : Nodal: Colors versus Alphas?



jeric_synergy
02-20-2011, 12:41 PM
Some monochromatic nodes have alpha channels, but I'm not understanding what the difference is between, say, the Turbulent Noise Color channel versus the Turbulent Noise Alpha channel.

I can see how the Color channel might present 3 identical values (since it's monochromatic), and the Alpha will always be 1 grayscale value.

For monochromatic nodes, is the data essentially the same? If you run a vector output into a scalar input, it's going to toss the 2nd and 3rd values, right?


Also, it would be nice if there were a facility to quickly see what the alpha channel of a given node looked like, without temporarily unwiring part of your network.

RebelHill
02-20-2011, 01:19 PM
because any of those nodes have colour... BG and FG colour values... none of them are monochromatic.

The alpha is simply an output that presents a mono version of the procedural as a scalar 0>1 for uses where you may want to use that. In this case, areas of teh procedural which are represented by teh FG colour appear as the 1 (white) value, and the BG colour areas 0 (black). however the actual gradient between the 2, and the level, is not influenced by either the setting of the BG or FG colour, nor the blending mode, but only by the texture parameters.

oh, and for previewing teh alpha, or other component, right click on the node ad set the preview type in its menu.

jeric_synergy
02-20-2011, 08:29 PM
1/2 "teh", 1/2 "the", LOL.

So, for those nodes, the "Alpha" is really simply the gray scale. Whereas, say, for "Grid", the alpha has nothing to do with the specific colors used, and instead is more of a pattern.

RMB Preview:Alpha!!! THANKS! :thumbsup: Now I just need the Cube preview and my life is complete!

Preview=BUMP.... whoa...Red and Green... time to hit the books some more.

jameswillmott
02-20-2011, 08:59 PM
Preview=BUMP.... whoa...Red and Green... time to hit the books some more.

Bump is a vector, a direction defined by three values. Colour is also a vector defined by three values, and you can visualise a vector as a colour where X is red, Y is green and Z is blue.

Normal maps do this ( although they remap -1 to 1 vector to 0 to 255 colour since not all image formats support negative values.)

dwburman
02-21-2011, 09:15 AM
so... You can have the BG and FG set to white but the alpha is unaffected. Cool. It IS affected by stuff plugged into the opacity channel.

RebelHill
02-21-2011, 09:39 AM
yes, bg and fg colour can be set to anything at all, as well as the blending mode between them, and the alpha is unaffected. This is the same for all procedural nodes, not just grid... the alpha isnt a greyscale representation of the colours, its jsut a greyscale representation of the actual procedural/pattern itself.