Transformation Matrix Tool

MartinRinehart

@chris fullmer said:

I have to say that one of my big confusions is that [the tutorial appendix] starts by talking about a 1x3 and a 3x3 matrix. While the information is true, it is confusing because SU uses the 4x4 matrix.

What I knew, and should have said, is that there really isn't a 4x4 matrix. If this were first done in an OO world we'd have a transformation object that combined a 3x3 scale/rotate array and a 3d translation vector.

The new version includes this bit of table art in the intro:

Thanks for helping make this clear.

thomthom

I have seen Wt to be other than 1.0

MartinRinehart

@chris fullmer said:

you state:

The translation vector's origin point is unspecified. SketchUp's translation is always relative to the [0,0,0] origin.

I think that is wrong inside of Components definition where it uses the def's origin as 0,0,0

I dunno. Try these two:

I'm not positive about SU, but I am positive that the Transformation Matrix hack was worth the effort. At least we can talk about these things.

MartinRinehart

@thomthom said:

I have seen Wt to be other than 1.0

I'd love to have an example!

thomthom

I don't remember exactly where I saw it. But I think Chris came across it recently while working on his Random Rotate and Scale plugin. I belive he'll be able to fill in the details here.

TIG

This is the whole story ?

Chris Fullmer

@martinrinehart said:

I'd love to have an example!

Take a component and use a uniform scaling method on it.

t = Geom::Transformation.scaling 0.5 my_comp.transform! t

They have applied uniform scaling by adjusting the 16th element. HOWEVER this caues problems with faceme components. Try it on one, and then orbit the model. The comonent gets all jumpy. This is a new bug in 7.1. The scaling method has worked the same way in previous version of SU, it is just how SU displays faceme's whose 16th element is not 1 has broke in 7.1. A bug has been filed and I'm begging them to get a fix out for 7.1 and not put it off until 8.0.

I'll take a closer look at the new explanataion Martin. I think it looks hopeful that I might get this learned yet!

Chris

MartinRinehart

According to Wikipedia, affine transformations never change Wt so it remains a 1. Perspective transformations do change it.

I mention this in hopes that someone who understands will explain it to the rest of us.

honoluludesktop

Martin, My apologies;-) at third glance, it is illustrated, now that I know what I am looking at:-) Thanks.

MartinRinehart

@honoluludesktop said:

Martin, My apologies;-)

Apologies not needed. Besides, you're the only guy here who has the correct version number on Win XP.