Rink a Dink Redux - Morphing Shapes - Question

[Jobbo]

Rink a Dink Redux by Paradroid of Lemon is amazing!!!

More than any other recent demo this has inspired me to revisit coding on the Amiga.

One effect that really impresses me is the morphing tetrahedron shapes which were apparently inspired by the same effect in the C64 demo Edge Of Disgrace.

This is the part I mean at the 4:00 mark: [ Show youtube player ]

I'd really like to do something similar myself but I have one really nagging question: How do you generate those shapes and the animation?

I've started to replicate the same animation in Blender, but I'm a Blender noob and also OMG those shapes make my brain hurt!

I can carry on with this approach, but I just wondered if anyone knows more about how the animation for that effect was created either on the Amiga or C64.

Really I would also be interested to hear just how much people think it's real time or not on both platforms? The C64 version especially just seems completely impossible to me, but then I know very little about C64 coding.

[a/b]

Switch objects, new object has some of the points at the same 3D coords (so it looks like the old object), morph points to new coords.
Not sure if that's how it's done but that how I would do it.

[Jobbo]

Sure, that's what I imagine the run-time does. Not sure if the lerping is real-time or precalculated but don't imagine that matters much.

What I was really getting at is how did they create the animation data? Is there some beautiful formula that I'm not aware of to calculate the mesh for the next morph target in each stage. For now I'm just doing it in Blender with a clunky combination of subdividing to figure out the target verts and then just manually moving the vertices on a cloned shape, eventually ending up with one mesh that can morph from a to b.

But I don't did this for the first of the morphs, it's going to be painful doing that for all the stages the shape goes through.

[a/b]

Ah, now I understand what you meant...
Not being very artsy myself I would do this in Blender:
- replicate points in object1
- move them away in the directions of where they should be in object2, so you have a rough approximation
- save as object1
- create the precise object2
- save as object2
And then write a simple tool that would load both and:
- loop through points of object1 (correct vertex order and polygon definitions) and for each find the closest point in object2 (wrong order/definitions but correct 3d coords)
- replace approximate coords from object1 with correct coords from object2

[Jobbo]

Yeah, that is something like what I'm already part way through doing.

But it's the creating of the target shapes that is quite mind melting!

[Jobbo]

For anyone curious I was eventually able to write an obj exporter to generate the same shape sequence.

Interestingly enough I also learned these are derived from what are known as the Platonic Solids, which are quite fascinating when you read the background.