Updated 10/17 request, reference to good 3d knee for Transformers hey tfw2005 artists... I'm just wondering if anyone has ever made a fully working knee joint or has reference pictures of one for a 3d model and animation I've been stuck on. Typically Transformers toys and comics use the one axis pin/cylinder system that caps at out about 100° max rotation... (such as featured TFW artist WeeWoo's RID Prime has and Don Figueroa and the IDW and DW artist draw) I'm looking for 150° rotation, currently using Gundam duel-knees as reference (EJ Su I've noticed has something similar)... but because of the large feet and lack of high ankles they aren't quite working as planned... too much dip through the floor at 30°... I'm sure other people have run into this snafu before... Any help or pointers or points in the right direction (reference pics!) highly appreciated! Thanks!
Another option is to allow the back of the lower leg to have a retractable or collapsable section, thus allowing partial penetration of the upper leg segment into the lower without leaving the lower leg with a gaping hole when the leg is straight.
That's what I do; often a combination of a sliding panel and a knee joint that can extend out of the lower leg to allow movement (I use that trick on shoulders and elbows too).
Update to Original Post Okay... thanks for the replys! However I probably should've made an image like this in the first place... I want to create a knee that's capable of 150° of rotation for an animation... that's the goal. Typically in even the best comics and fan art (and toys)... in both 3d and 2d a cylinder/pin hinge joint system is used for TF knees... which looks cool in stills, but is well... not enough for good animation purposes. I made a little drawing here... it shows your typical robot leg... I moved the pivot point around to show the issues that I've come across... With the Foward Pivot Point, floor collision is acceptable, but maximum rotation before mesh collision is only 50°... give or take 15 or so. With the Rear Pivot Point floor collision is too extensive, but the maximum rotation is perfect. HOWEVER the leg is actually extending... growing in size... significantly. That's no good... useable maybe though trick cameras and slight of hand... but not good enough... With the Centered Pivot Point floor collision is a bit too much, and the max rotation is around only 85°... this is what the majority of figures use... you can get creative with the geometry and get about 110° out of it (Classics OP and I from what I gathered Gemini is talking about) but that's barely enough for a realistic run cycle... sitting... kneeling... it's very limiting. With humans, our joints are capable of a bit of compression and over extension and our skin deforms... but with TF's being made of metals, that's just not an option. Mesh collision is a no. And I'm making a more simple G1 style guy (Optimus/Soundwave) nothing like the new TFTM'07 with super complex SDKs and scripts and what not... The floor issue is a problem for floor contacts I intend on using... raising the body up when the toe rolls looks silly... Transformers unlike Gundams don't usually have high ankles either... if they even have ankles at all. So yeh, there you have it. Without some second degree movement and shifting this system is well, hard to figure out. Even with the Dual Hinge, I haven't figured it out completely yet without giving the TF dancer legs and high ankles like a Gundam... Gundams rock... but they have female proportions... not what I'm going for right now. If you have a solution I'd appreciate a tip or two or namely, an image or playblast...
Remember, even if it seem that mesh collision will happen or meshes look too close together, you can always bevel or chamfer the corners to create more room.
