Blend Op Primary Transforms

[Mcronin]

OK, the the Blend Op apparently has primary and secondary transforms, how do I get at the primary ones? blend/tx seems to point at the secondary. The primary transforms are the result of the blend operation, and those are the ones I need. I'd like to use the Blend Op and I'm only interested in three specific channels so parenting is out. Anyone know how to reference them?

[edward]

Blend VOP? Blend SOP? Blend Obj?

[FrankFirsching]

You can use the expressions "origin" and "originoffset" along with a null-object at the world-origin. Since the function origin only returns the values for translation and rotation, one has to do some complicated stuff with the originoffset-expression to compute the scale-values. Here is it for scaleX:

vlength(vector3(originoffset("Origin", "[0,0,0]", "blend1", "[1,0,0]", "TX"), originoffset("Origin", "[0,0,0]", "blend1", "[1,0,0]", "TY"), originoffset("Origin", "[0,0,0]", "blend1", "[1,0,0]", "TZ"))-vtorigin("Origin", "blend1"))

Unfortunately there is no vtoriginoffset, which would make this expression much easier.

BlendedButNotParented.hip

[edward]

As a sidenote in H6, you can simply give it the empty string "" to mean worldspace without always making sure you have some dummy object in the origin.

[FrankFirsching]

thanks edward. very good to know. I think it's high time to switch to version 6 for me.

[Mcronin]

I'm sorry, yeah, the Blend Obj. Thanks for the file Frank, but I'm getting a failed to load error with it. What version is it from?

Maybe a better explanation of what I'm trying to do will help.

I'm trying to set something up, Kinda like the IK/FK blending, but what this will do is provide a hud slider that will allow an animator to blend between an automatic handle and a handle they can key. I figure that the sequence blend is a good way to go, but I think I have to reference the channels because I don't want to blend them all. The user handle allows the user to control all transform channels, the automatic handle controls only three. I don't want to blend them all, the blend type requires two sliders and it "pops", so I would like to use sequence blend, but no matter how I parent or reference the channels I know how to access, it's just not right. I get double transforms, half transforms, and/or blending between channels I don't want. I don't mind using expressions, I just don't want to use some kludge like multiplying channels by .5 or 2.

I'll take a look at origin and originoffset. I only need tranaslate and rotate channels so it might work out. I'm not particularly good with CHOPs but I'm wondering if maybe there's a way to do it there. What do you guys think?

[FrankFirsching]

I'm using Houdini 5.5.305. Don't know, why you can't open it. I didn't do anything weired. Just expressions.

But I have another idea: why don't you use the blend-operation of the OP and set the "Weight 1" to 1-ch("blendw2"). This way you emulate the behavior of the sequence-mode with 2 inputs. But using this mode you are able to turn off the transform-flags, you are not interrested in. Now it should be possible to parent your blended node to the blend-OP.

In case you don't want or can't do so, here are the expressions I used for translation and rotation:

translation:
origin("Origin", "blend1", "TX")
origin("Origin", "blend1", "TY")
origin("Origin", "blend1", "TZ")
rotation:
origin("Origin", "blend1", "RX")
origin("Origin", "blend1", "RY")
origin("Origin", "blend1", "RZ")

[edward]

I'd stick to the Sequence Blend mode within the Blend Object so that you can make use of "Shortest Path Rotation Blending". After that you can use the expressions as mentioned by Frank to get at the result. If you need more complex control of the resulting transform, then I would recommend using the Object CHOP.

[Mcronin]

Thaks guys, if this works out it should be pretty cool! Thanks for all the help.

BTW I wasn't sure if this was the right forum to put this in. If I have more questions like this should I put them in General or Character or put them here?

[edward]

Personally, I don't see how this relates to VEX so I'd vote for any non-VEX forum

[Mcronin]

Yeah, the only reason why I put it here was because I figured the solution was probably going to involve some typing I guess next time it'll be general or character.