Alright, I've finally got time to continue working on this. Nothing new to see at the moment, sorry.

I have a question regarding matrices, maybe somebody can help? For all building elements I am storing a 4x4 matrix that contains scaling, translation and rotation data (I use the "SRT to Matrix" node). Now I will need to store additional information for some elements, such as extrusion length, floor type etc. I would like to store all of this additional data in the same 4x4 matrix because that would keep things neat and clean.

It appears that the LAST COLUMN of this matrix always says 0,0,0,1 - regardless of what values I choose in the "SRT to Matrix". Am I right in assuming that I can simply use these 4 slots to store scalar data without EVER destroying the SRT info?

I suppose you could as long as you are very careful to set those values back before using the matrix as a transform in any way because once you change those values, the matrix no longer represents a valid transformation. However, I don't think that all the packing and unpacking of matrices that would be required is any more "neat and clean" than storing separate attributes -- quite the opposite in fact.

I need to keep all these value arrays in sync. Every rule needs to update every array. I figured that maintaining only one matrix array is the best solution, but maybe separate arrays are better. I'll take a look, thank you!

I wouldn't store data in the transformation matrix, it seems predestined to bite you in the butt later on. And in doing so you will have moved from storing all data in an open, shared way to essentially storing data in a custom format that requires a translation layer.

Also, you may want more than three or four scalar values later on, or to store data of different types. You are almost certainly better storing data in multiple arrays and using an ID to keep everything in sync.

Yes, I think you're both right. That's how I'll do it. It's good that I cleared this up right away, because it's such an important part of the system, and having to change it all way down the line would be a nightmare.

Chris,

The 4 x 4 Matrix is called Homogeneous Transform Matrix. Here are some information concerning the matrix and its use in graphics:

http://blogoben.wordpress.com/
http://www710.univ-lyon1.fr/~jciehl/Public/OpenGL_PG/apf.html
http://math.hws.edu/graphicsnotes/c3/s1.html
http://www.cs.iastate.edu/~cs577/handouts/homogeneous-transform.pdf
http://graphics.ucsd.edu/courses/cse167_f05/CSE167_03.ppt

Cheers!

Dan

BTW, word of caution concerning matrices from Matt Lind at XSI List:



Good explaination of row and column vectors here:

http://www.cse.ttu.edu.tw/~jmchen/cg/docs/rendering%20pipeline/rendering/vector_matrix.html#transpose

P.S. OpenGL is column vertors based

Thanks for the links, Daniel!

Oh my god this is so great!! I too was thinking it would be possible to generate cities with ICE and was a bit dissapointed when i saw the videos on youtube that just deal with floor numbers.

I originally got really inspired when i saw this: http://www.youtube.com/watch?v=-d2-PtK4F6Y&feature=feedlik wich has nothing to with ICE - but is just damn cool.

You're really far along already!!

I'm gonna read your post more carefully and try to reproduce it but i just had to respond immediatly when i skimmed it - it's just great when someone has the same vision and has already done a lot of the legwork!

Yes, it's been a while since I posted an update. But I have kept on working on this. I've done a ton of stuff under the hood to ensure proper usability. I don't know how often I've modified my split compound now, but it's become a powerhouse, so that was worth it.

I'm planning on showing the current functionality in a video hopefully on Monday.

hey Chris this is looking awesome! I'll sure keep up reading this thread for updates