• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
stu_pidd_cow

[Assimp] Getting bind pose bone positions

4 posts in this topic

I'm trying to get my head around animation and Assimp. I'm trying to just get the bone positions in bind pose (no animation or anything like that). According to various sources, I should be able to use aiBone::mOffsetMatrix. The way I am doing it is (psuedo code):

MthVector4 v(0.0f, 0.0f, 0.0f, 1.0f);
MthMatrix invOffset = mOffsetMatrix;
invOffset.Inverse();
invOffset.Transform(v, v);
pos = (MthVector3&)v / v.w;

pos should give the position in model space, right? I've spent a while fiddling around with this stuff for a while but nothing looks right at all. So what is the correct way to do this?

 

Thanks.

0

Share this post


Link to post
Share on other sites

Ok, maybe a clearer question would be: What are aiBone::mOffsetMatrix and aiNode::mTransformation, what is the difference and when/how should I use them?

 

Thanks.

0

Share this post


Link to post
Share on other sites

To my knowledge, assimp does not store bind pose.

 

The skeleton you have is stored in whatever frame 1 is.

 

The offset matrix is what you need to multiply a vertex (taking the joint's weight into account) by in order to get it into the bone space of frame 1.

 

I love assimp, but i can't stand the datastructures / orgonization / matrix handedness they chose.

1

Share this post


Link to post
Share on other sites
I got headache when I have worked on skinning with Assimp. Uglydavis has right, no bind pose.

I had to take a look to Assimp model viewer source code to get it working.

The bone matrices should be computed like that (or reverted depending of your matrix convention):

BoneWorldTransform * BoneOffsetMatrix * InverseRootNodeWorldTransform

Root node, is the root node of the aiScene (not the skeleton root node).

Hope this helps ! Edited by DTR666
1

Share this post


Link to post
Share on other sites

What you're doing appears to be fine. If you need more help, you'll have to provide more information than "nothing looks right."

 

I'm not particularly familiar with Assimp, but, as mentioned above, the offset matrix transforms a position in root node space to bone space. For example, assume a mesh vertex is positioned (0, 20, 5) with respect to the root node. If a bone is positioned at (0, 19, 4) with respect to the root node, the offset matrix will transform the position to ( 0, 1, 1) (ignoring rotations and scaling).

 

According to the Assimp docs, mTransformation is a bone's orientation with respect to its parent bone.

Edited by Buckeye
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0