GIMPACT uses the Right Hand Coordinate System:

Figure 2.1. Right Hand Coordinate System

Object surfaces are often represented as discrete aproximations which consists on a set of vertices and triangular faces.

A trimesh has the following attributes:

Take the following trimesh example:

Figure 2.2. Trimesh.

Notice that:

GIMPACT design was developed in mind for taking advantage of multi-processing capabilities of modern computers and also for distributed architechture enviroment (GRID Processing).

For that reason GIMPACT implements a memory management system which allows getting access to data wich would comes from many memory sources (System memory, GPU video memory etc.) althougt it protects the memory access on concurrent processes. For example , in a modern PC we will found the following memory sources:

But at this moment, GIMPACT only suports system memory access. In next releases it will support paralele processing and SIMD instructions.

GIMPACT have these memory management systems: Buffers and Dynamic arrays.

3.1. Buffers

A buffer refers to a memory resource which belongs to a Memory Manager. At this moment there are these avaliable memory managers :

• G_BUFFER_MANAGER_SYSTEM : Corresponds to allocated data in system memory by the malloc() function. It should be destroyed by GIMPACT when the program terminates.
• G_BUFFER_MANAGER_SHARED : Corresponds to data allocated in user application, like a pointer to another array. Shared use. It must be managed, initialized and released by the user.

GIMPACT requires to initialize its internal structures before using its memory routines.

	Important
	Before using GIMPACT, call this function gimpact_init() for initializing its internal structures.

	Important
	At end call gimpact_terminate() for releasing memory resources.

For creating memory buffers you would use the following methods:

• The generic way for creating buffers is using the gim_create_buffer() function, where buffer_manager_id is an Memory Manager Identifieres (G_BUFFER_MANAGER_SYSTEM, G_BUFFER_MANAGER_SHARED).
• For uploading memory to a buffer, use gim_upload_to_buffer()
• If you want to create a simple buffer on system memory, use gim_create_common_buffer().
• If you want to create a simple buffer from an existing data, use: gim_create_shared_buffer_from_data().

For accessing buffers like accessing to an array, use BUFFER ARRAYS. There is an example in BUFFER ARRAYS Details

GIMPACT supports collisions between moving trimeshes and deformable bodies. On each interval simulations could modify the state of the trimesh, applying a linear transformation or changing their vertices directly. Then Trimeshes will update their structures quickly in a execution time near to O(log(n)) .

5.2. Linear Transformations

GIMPACT have matrix transformations with these types:mat2f,mat3f y mat4f. Matrices are row oriented:

Figure 2.3. Linear Transformation.

Para saber como aplicar transformaciones lineales a los vertices de una superficie triángular, vease TRIMESH.

For accelerating the collision process it is necessary to avoid expensive calculations detecting which pairs of objects won't intersect.

So it is necessary to approximate objects geometry to simple shapes like spheres or rectangular boxes:

Figure 3.1. Shape interference.

1.1. Rectangular Boxes :AABB

AABB means Axis Aligned Bounding Box, which is used for approximating the space ocupied by a solid object:

Figure 3.2. AABB.

1.2.  Finding Interferences on a Room

One of the most common collision problems is finding which pairs of objects are near to intersect. This stage of process is known as Broad Phase, which consists of verify very quickly which objects could intersect, by evaluating AABB collisions. With this previus verification is posible to avoid expensive calculations implied on detailed collisions per triangle based.

See how is posible to avoid executing collision commands when objects won't intersect, independently of their geometric shape.

Figure 3.3. Object Interferences.

For avoid executing NxN compairisons, GIMPACT uses a sweep based technique which orders AABB corners, reducing the complexity to O(log(N)); In many cases we have a linear complexity of O(N). This technique is known as Box Prunning.

See how to find collision pairs on gim_aabbset_self_intersections(). Also visit BOX_PRUNNING

See gim_trimesh_trimesh_collision().

See gim_trimesh_sphere_collision().

See gim_trimesh_capsule_collision().

Will be implemented in next releases of GIMPACT.

Will be implemented in next releases of GIMPACT.

May be implemented in next releases of GIMPACT, but since trimeshes can be convex polyhedrons it won't be strictly necessary.

Integrating GIMPACT with ODE has had successfully results. Now is possible to make physical collisions between moving trimeshes correctly:

Figure 4.1. ODE physics with GIMPACT trimesh collision.

Download the new version of ODE with GIMPACT at: ode-gimpact.zip.

	Important
	CODE::BLOCKS IDE with MingW compiler are highly recommended for building ODE-GIMPACT sources. Download a copy of CODE::BLOCKS 1.0 RC3 from: CODE::BLOCKS.zip. Download a copy of MingW 3.4.5. compiler from: Mingw345.zip.

	Important
	Some additional commands must be called for supporting the new changes to ODE. At the beginning of the application, dInitODE() must be called. At the end, dCloseODE() must be called.

Gammaleon is a 3D engine which integrates physics on its simulations. Organizes the worlds in Rooms and Sectors.

Figure 4.2. Gammaleon Physics collision.

Gammaleon uses ODE and GIMPACT for implement complex physics simulations. Its most outstanding features are:

Download Gammaleon at: gammaleon.zip.

	Important
	CODE::BLOCKS IDE with MingW compiler are highly recommended for building Gammaleon sources. Download a copy of CODE::BLOCKS 1.0 RC3 from: CODE::BLOCKS.zip. Download a copy of MingW 3.4.5. compiler from: Mingw345.zip.

CODE::BLOCKS has been the most successfull Free IDE for C/C++ programming. It is highly recommended for building GIMPACT sources, although Mingw compiler is strongly used:

Documentation in process.

Documentation in process.