I guess it would be very handy to be able to… “customize”(?) the generation of the automation curve in “curve” mode… Here is what I mean:
PS:
“can do” - is the only curve type we can produce in Renoise
“can NOT do” - are examples of the “wish-to-be-able-to-generate” curves.
about the first can-NOT-do curve:
I agree: concave curves should be available.
I have already reported this in the to-do list in our team-internal discussion thread.
about the second can-NOT do curve:
which kind of curve interpolation is that? I believe your sketch lacks of one point at local minimum (zero) and local maximum, otherwise you would not be able to interpolate the curve in an unambiguous way. Anyway, I understand that your point about th third sketch is that you would like to be able to change convexity of the envelope from a point to another. Wuold be cool, actually, but maybe too complex, since our envelope curves are not simple ADSR curves, but are n-Poles Bezier curves
yep… gotta admit that the second one is a little… “overheadous”, so I’m ready to agree for the first one at least 
As for the curve types… I think you are right - they are multipoles beziers… which however is not that hard to be implemented basing on the existing routines… IMHO
I didn’t make myself clear about this, sorry.
indeed I was not talking about implementation: I think it would be hard to make an user-friendly GUI to deal with multiple inflexion points; ADSR curves are easier to handle because you can only have four poles, and most of times the application let’s you specify concavity/convexity of attack and release only, while what you are asking is the ability to specify concavity/convexity of each group of two poles.
I see… But I’ve got an idea (simple enough to realize, I guess) of the curve “controlling” (with no need of any additional tools):
holding down some key user select curve segment between any two points and this segment get “inverted”. Just like this:
I want to combine curves and linears!
Yeah the curves in Logic and also Adobe Premiere Pro (not an audio app, but a curve is a curve) are excellent. SOOO nice to be able to drag the shapes around like rubber.
I would love something like this to be implemented in renoise
I can’t wait for future updates when the automation editor gets a big overhaul. It works fine right now, but could be so much better & more intuitive to work with imo. (drawing automation over more then 1 pattern, anyone?
Imo the resolution (amount of dots that can be placed within the automation ‘time’-grid) should be selectable regardless of the patternlength & trackspeed. If I’d for example like to have a resolution of 512 steps within a patternlength of 64 this is now impossible. You can zoom in, but can’t freely draw in dots 
Whatever curve options you want, even sudden steps (like a staircase with hard edges) are impossible without setting your patternlength to the maximum of 512.
hopefully scripting in renoise will be a succes, if one would be able to script automation envelopes over multiple patterns that would simply be orgasmic
Yeah it seems at the moment that the automation is kind only working in a SNAP mode. It would be nice to be able to freely draw where ever want on the window…
In reality it doesnt really make using renoise any worse for me now, as I dont really use automation a great deal, but it would be nice to have the option of free unquantised drawing
+1 For multiple curve types, the ones in acid pro are good, holding a key down and adjusting is a great idea though so that might be better than choosing from a list although both would be cool.
Yes I like this feature too, it really helps especially when your patterns are long.
And I agree that Automation panel lacks some flexibilities, it is logical that if curves are allowed, all types of them can be created. Along with Adobe Premiere Pro, 3D Studio MAX can also be a good example: each point’s tangent line can be customized and also there are some useful presets to create the prevalent form of curves just by a click.