What Blender Export should I use?

molma100 · **Joined:** Sat Apr 09, 2011 8:12 pm **Posts:** 11

im wondering how i would setup my mesh to have collision in bullet...

is there an export script(or whatever its called) in blender that i can use for Bullet Physics?

if so then please post a link, and i also wanna know how i would update my Blender to use this export..

Erwin Coumans · **Posted:** Wed Apr 20, 2011 5:18 am

The best is to use the built-in .bullet export in the Blender game engine, called through a Python command (the actual Bullet export happens in C/C++, unlike the common Python export scripts)

This requires Blender 2.57 (or later). Setup the collision shapes, rigid body info, constraints, soft body etc for the Blender game engine (BGE), hook up a BGE python script to a controller and run the BGE using the 'P' key/or menu. Here is the script:

Code:

import PhysicsConstraints;
PhysicsConstraints.exportBulletFile("testFile.bullet")

See also exportBulletFile.blend in this archive:
http://bulletphysics.com/ftp/pub/test/i ... iles-2.zip

It will export most collision shape types, rigid body info, constraints and soft body data in a .bullet file.
Thanks,
Erwin

molma100 · **Joined:** Sat Apr 09, 2011 8:12 pm **Posts:** 11

Hey i believe i have everything setup satisfyingly, but:

Erwin Coumans wrote:

hook up a BGE python script to a controller and run the BGE using the 'P' key/or menu. Here is the script:

i didnt completely understand what you were talking about. sorry, im not ultimately used to the new blender interface yet, you think you could give a few details?

also im glad for the answer

EDIT: i looked up some information and i figured out how to export it yay

now im wondering how i would use this in c++...

Erwin Coumans · **Posted:** Thu Apr 21, 2011 5:01 am

You can use btBulletWorldImporter.

See Bullet/Demos/SerializeDemo, it can load your .bullet file.
Thanks,
Erwin

molma100 · **Joined:** Sat Apr 09, 2011 8:12 pm **Posts:** 11

hey i got the importer to work, thanks to you xD but now im having another peoblem..

when i start my game, everything fine: gravity works and everything...

the only problem now, is that once my character falls, he falss through the landscape ._.

im wondering if something is wrong with the physics(i DID notice the box i set was moving slowly while on the plane in blender, i thought it was friction or whatever :/)

EDIT: hey i did some trial and error, and i found out that when i search for how many rigid bodies there are in the .bullet file, it says theres none...

is there a way to add them with the python code?

iwg_eric · **Joined:** Sat Apr 30, 2011 2:28 pm **Posts:** 8

Where did you find the .bullet file after running the script to export the file? I'm using Blender 2.57 and I believe the script is running (I see the print in the console and I added a print at the end which I also see in the console), but I can't find the .bullet file anywhere.

Thanks.

Erwin Coumans · **Posted:** Mon May 02, 2011 9:57 pm

The file should go in the current working directory, typically next to the Blender.exe, unless you start it from a debugger etc.

You can chose an absolute path, for example under windows:

Code:

PhysicsConstraints.exportBulletFile("c:/testFile.bullet")

Thanks,
Erwin

iwg_eric · **Joined:** Sat Apr 30, 2011 2:28 pm **Posts:** 8

Thanks, Erwin. Based on your response, I noticed that I was using "\" instead of "/" when I tried the absolute path. The file is being created now.

Thanks again.

vidjogamer · **Joined:** Thu Apr 29, 2010 11:59 pm **Posts:** 13

I am trying your script in Blender 2.6 and it says the module doesnt exist...

Do you know if it was it taken out? Renamed?

Edit, my apologies. It seems you cannot run the script from the text editor window and that you must run it in game. Thanks Erwin.

jacket · **Joined:** Thu Oct 01, 2009 1:23 pm **Posts:** 3

Erwin Coumans wrote:

You can use btBulletWorldImporter.

See Bullet/Demos/SerializeDemo, it can load your .bullet file.
Thanks,
Erwin

I got this export to work from Blender 2.62, but I've been trying to find a way to identify the object by it's Blender name.

According to the Bullet binary serialization doc:

http://bulletphysics.org/mediawiki-1.5.8/index.php/Bullet_binary_serialization#Setting_and_Getting_the_name_for_bodies.2C_shapes_and_constraints

Quote:

Setting and Getting the name for bodies, shapes and constraints

The Dynamica Maya plugin and Blender create unique names for all objects. This is useful to recognize objects, shapes and constraints, for example to bind them with graphics objects.
When saving the file, the btDefaultSerializer is created, and all names are registered using the registerNameForPointer method.
When loading the .bullet file, the m_name field is part of the structures: btCollisionObjectData, btRigidBodyData, btCollisionShapeData and btTypedConstraintData.
Also the 'btBulletWorldImporter::createRigidBody' methods passes this nams as one of the arguments, when available.

However, the name is always exactly the same as the collision shape name, rather than a unique Blender name. This code:

Code:

   int i;
   for (i=0; i < m_dynamicsWorld->getNumCollisionObjects(); i++)
   {
      btCollisionObject* obj = m_dynamicsWorld->getCollisionObjectArray()[i];
      btRigidBody* body = btRigidBody::upcast(obj);
      
      printf("  object name = %s\n", body->getRootCollisionShape()->getName());
...

produces:

Quote:

object name = Box

for every box collision shape.

jacket · **Joined:** Thu Oct 01, 2009 1:23 pm **Posts:** 3

Ok, I figured it out. It's not part of the btRigidBody object, but it must be extracted from the btBulletWorldImporter object:

Code:

   class btBulletWorldImporter*      m_fileLoader;
       ...

   int i;
   for (i=0; i < m_fileLoader->getNumRigidBodies(); i++)
   {
      btCollisionObject* coll =  m_fileLoader->getRigidBodyByIndex(i);
      btRigidBody* body = btRigidBody::upcast(coll);
      
      printf("  object name = %s\n", m_fileLoader->getNameForPointer(body));   // The Blender object name
        ...

jacket wrote:

Erwin Coumans wrote:

You can use btBulletWorldImporter.

See Bullet/Demos/SerializeDemo, it can load your .bullet file.
Thanks,
Erwin

I got this export to work from Blender 2.62, but I've been trying to find a way to identify the object by it's Blender name.

According to the Bullet binary serialization doc:

http://bulletphysics.org/mediawiki-1.5.8/index.php/Bullet_binary_serialization#Setting_and_Getting_the_name_for_bodies.2C_shapes_and_constraints

Quote:

Setting and Getting the name for bodies, shapes and constraints

The Dynamica Maya plugin and Blender create unique names for all objects. This is useful to recognize objects, shapes and constraints, for example to bind them with graphics objects.
When saving the file, the btDefaultSerializer is created, and all names are registered using the registerNameForPointer method.
When loading the .bullet file, the m_name field is part of the structures: btCollisionObjectData, btRigidBodyData, btCollisionShapeData and btTypedConstraintData.
Also the 'btBulletWorldImporter::createRigidBody' methods passes this nams as one of the arguments, when available.

However, the name is always exactly the same as the collision shape name, rather than a unique Blender name. This code:

Code:

   int i;
   for (i=0; i < m_dynamicsWorld->getNumCollisionObjects(); i++)
   {
      btCollisionObject* obj = m_dynamicsWorld->getCollisionObjectArray()[i];
      btRigidBody* body = btRigidBody::upcast(obj);
      
      printf("  object name = %s\n", body->getRootCollisionShape()->getName());
...

produces:

Quote:

object name = Box

for every box collision shape.

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What Blender Export should I use?

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