This is Info file solid2.info, produced by Makeinfo version 1.68 from
the input file solid2.texi.

START-INFO-DIR-ENTRY
* SOLID: (solid2).      Software Library for Interference Detection.
END-INFO-DIR-ENTRY

   This file documents the features and implementation of SOLID.

   Copyright (C) 1997-1999  Gino van den Bergen

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the section entitled "GNU Library General Public License" is
included exactly as in the original, and provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the section entitled "GNU Library General Public
License" and this permission notice may be included in translations
approved by the Free Software Foundation instead of in the original
English.


File: solid2.info,  Node: Top,  Next: Copying,  Up: (DIR)

   Introduction

   This manual documents how to install and use SOLID.

* Menu:

* Copying::	    GNU Library Public License says how you can copy
                    and share SOLID.
* Introduction::    What is it?
* Installation::    How to configure, compile and install SOLID.
* Trouble::         If you have trouble installing SOLID.
* Usage::           How the API is set up.
* Projects::	    Things Still Left to do
* Bugs::            Where to send bugs reports and questions.


File: solid2.info,  Node: Copying,  Next: Introduction,  Prev: Top,  Up: Top

GNU LIBRARY GENERAL PUBLIC LICENSE
**********************************

                         Version 2, June 1991

     Copyright (C) 1991 Free Software Foundation, Inc.
     59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
     Everyone is permitted to copy and distribute verbatim copies
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   That's all there is to it!


File: solid2.info,  Node: Introduction,  Next: Installation,  Prev: Copying,  Up: Top

Introduction
************

   SOLID is a library for collision detection of three-dimensional
objects undergoing rigid motion and deformation.  SOLID is designed to
be used in interactive 3D graphics applications, and is especially
suited for collision detection of objects and worlds described in VRML.
Some of its features are:

   * Object shapes are represented by primitive shapes (box, cone,
     cylinder, sphere), and complexes of polytopes (line segments,
     convex polygons, convex polyhedra). A single shape can be used to
     instantiate multiple objects.

   * Motion is specified by translations, rotations, and nonuniform
     scalings of the local  coordinate system of each moving object.
     These changes can be given absolute or relative to the previous
     frame. The local coordinate system can also be set according to an
     array of sixteen floats or doubles representing a 4x4 column-major
     matrix of an affine transformation, as used in OpenGL.

   * Deformations of complex shapes can be specified using
     client-defined vertex arrays.

   * Collision response is defined by the client by means of call-back
     functions. Response may be defined per object pair, for all pairs
     containing a specific object, and as default for all pairs of
     objects.

   * Response call-backs can use collision data describing the
     configuration of a pair of colliding objects. As collision data
     can be used: a point common to both objects, or the closest point
     pair of the objects from the previous frame. The latter response
     type can be used for approximating the collision plane in
     physics-based simulations.

   * Frame coherence is exploited by maintaining a set of pairs of
     proximate objects (incremental sweep and prune of axis-aligned
     bounding boxes), and caching separating axes for these pairs.
     This feature is optional and may be turned on/off at any time
     during a simulation.


File: solid2.info,  Node: Installation,  Next: Trouble,  Prev: Introduction,  Up: Top

Installing SOLID
****************

Requirements
============

   The library is written in standard C++ and relies heavily on the
STL. Currently, it compiles under GNU g++ version 2.8.1 and up.  The
library has a standard C API and can be linked to both C and C++
applications. In order to link it to C applications you need the
libstdc++ library.

Installation
============

   In case you have a recent GNU developers environment installed,
simply typing `make' in the root of the distribution directory will
build the library, a sample client and documentation.

   If you want to use another compiler, you should make the necessary
changes to the `Make-config' file in the root directory. See the
comments in this file for details.

   The auxiliary C++ classes in `include/3D' for performing affine
transformation in 3D have all their code inlined, so you do not need to
link a library in order to use them.


File: solid2.info,  Node: Trouble,  Next: Usage,  Prev: Installation,  Up: Top

Trouble in Installation
***********************

   Q: My compiler cannot figure out the templates used in the SOLID
source! What's the matter?

   A: Your compiler does not comply with the ISO standard for C++.
Install the GNU g++ compiler version 2.8.1 or higher for your platform.


File: solid2.info,  Node: Usage,  Next: Projects,  Prev: Trouble,  Up: Top

The SOLID API
*************

Building Shapes
===============

   The commands for creating and destroying shapes are
     DtShapeRef dtBox(DtScalar x, DtScalar y, DtScalar z);
     DtShapeRef dtCone(DtScalar radius, DtScalar height);
     DtShapeRef dtCylinder(DtScalar radius, DtScalar height);
     DtShapeRef dtSphere(DtScalar radius);
     DtShapeRef dtNewComplexShape();
     
     void dtDeleteShape(DtShapeRef shape);
   Shapes are referred to by values of `DtShapeRef'.  Currently, the
type `DtScalar' is defined as `double'.  The command `dtBox' creates a
rectangular parallelepiped centered at the origin and aligned with the
axes of the shape's local coordinate system.  The parameters specify
its extent along the respective coordinate axes.  The commands `dtCone'
and `dtCylinder' create respectively a cone and a cylinder centered at
the origin and whose central axis is aligned with the Y-axis of the
local coordinate system.  The cone's apex is at y = height / 2.  The
command `dtSphere' creates a sphere centered at the origin of the local
coordinate system.

   Other shape types based on point data, such as polygon soups,
simplicial complexes, (compositions of) convex polyhedra, are created
by the `dtNewComplexShape' command.  For constructing complex shapes
the following commands are used:
     DtShapeRef dtNewComplexShape();
     void dtEndComplexShape();
     
     void dtBegin(DtPolyType type);
     void dtEnd();
     void dtVertex(DtScalar x, DtScalar y, DtScalar z);
     
     void dtVertexBase(const void *base);
     void dtVertexIndex(DtIndex index);
     void dtVertexIndices(DtPolyType type, DtCount count, const DtIndex *indices);
     void dtVertexRange(DtPolyType type, DtIndex first, DtCount count);
   A complex shape is composed of d-dimensional polytopes, where d is
at most 3.  A d-polytope can be a simplex (point, line segment,
triangle, tetrahedron), a convex polygon, or a convex polyhedron.  The
type of d-polytope is specified by a value of `DtPolyType', defined as
     typedef enum DtPolyType {
       DT_SIMPLEX,
       DT_POLYGON,
       DT_POLYHEDRON
     } DtPolyType;
   A d-polytope is specified by enumerating its vertices. This can be
done in two ways. In the first way, the vertices are specified by value,
using the `dtVertex' command. The following example shows how the faces
of a pyramid are specified.
     DtShapeRef pyramid = dtNewComplexShape();
     
     dtBegin(DT_SIMPLEX);
     dtVertex(1.0, 0.0, 1.0);
     dtVertex(1.0, 0.0, -1.0);
     dtVertex(-1.0, 0.0, -1.0);
     dtVertex(-1.0, 0.0, 1.0);
     dtEnd();
     
     dtBegin(DT_SIMPLEX);
     dtVertex(1.0, 0.0, 1.0);
     dtVertex(1.0, 0.0, -1.0);
     dtVertex(0.0, 1.27, 0.0);
     dtEnd();
     
     ...
     
     dtEndComplexShape();
   In the second method, the vertices are stored in an array, and are
referred to by indices.  For each complex shape, we can specify a
single array.  A vertex array is specified by  the command
`dtVertexBase', which takes the address of the first element in the
array, referred to as the base of the array, as argument.  The command
`dtVertexIndex' is used for specifying vertices. See the following
example:
     DtScalar vertices[5 * 3] = {
       1.0, 0.0, 1.0,
       1.0, 0.0, -1.0,
       -1.0, 0.0, -1.0,
       -1.0, 0.0, 1.0,
       0.0, 1.27, 0.0
     };
     
     DtShapeRef pyramid = dtNewComplexShape();
     dtVertexBase(vertices);
     
     dtBegin(DT_SIMPLEX);
     dtVertexIndex(0);
     dtVertexIndex(1);
     dtVertexIndex(2);
     dtVertexIndex(3);
     dtEnd();
     
     dtBegin(DT_SIMPLEX);
     dtVertexIndex(0);
     dtVertexIndex(1);
     dtVertexIndex(4);
     dtEnd();
     
     ...
     
     dtEndComplexShape();
   Alternatively, the indices can be placed into an array and specified
using the command `dtVertexIndices', as in the following example:
     DtScalar vertices[5 * 3] = {
       1.0, 0.0, 1.0,
       1.0, 0.0, -1.0,
       -1.0, 0.0, -1.0,
       -1.0, 0.0, 1.0,
       0.0, 1.27, 0.0
     };
     
     DtIndex face0[4] = { 0, 1, 2, 3 };
     DtIndex face1[3] = { 0, 1, 4 };
     
     ...
     
     DtShapeRef pyramid = dtNewComplexShape();
     dtVertexBase(vertices);
     
     dtVertexIndices(DT_SIMPLEX, 4, face0);
     dtVertexIndices(DT_SIMPLEX, 3, face1);
     
     ...
     
     dtEndComplexShape();
   Finally, a polytope can be specified from a range of vertices using
the command `dtVertexRange'.  The range is specified by the first index
and the number of vertices.  In the following example a pyramid is
constructed as a convex polyhedron, which is the convex hull of the
vertices in the array.
     DtScalar vertices[5 * 3] = {
       1.0, 0.0, 1.0,
       1.0, 0.0, -1.0,
       -1.0, 0.0, -1.0,
       -1.0, 0.0, 1.0,
       0.0, 1.27, 0.0
     };
     
     DtShapeRef pyramid = dtNewComplexShape();
     dtVertexBase(vertices);
     dtVertexRange(DT_POLYHEDRON, 0, 5);
     dtEndComplexShape();

   Note that the vertices of a simplex need not be affinely independent,
and the vertices specifying a convex polyhedron need not be extreme
vertices of the convex hull.  However, in order to construct a proper
convex polygon, the vertices should be approximately coplanar and
specified in the order as they appear on the boundary.

Creating and Moving Objects
===========================

   An object is an instance of a shape.  The commands for creating,
moving and deleting objects are
     void dtCreateObject(DtObjectRef object, DtShapeRef shape);
     void dtDeleteObject(DtObjectRef object);
     void dtSelectObject(DtObjectRef object);
     
     void dtLoadIdentity();
     
     void dtLoadMatrixf(const float *m);
     void dtLoadMatrixd(const double *m);
     
     void dtMultMatrixf(const float *m);
     void dtMultMatrixd(const double *m);
     
     void dtTranslate(DtScalar x, DtScalar y, DtScalar z);
     void dtRotate(DtScalar x, DtScalar y, DtScalar z, DtScalar w);
     void dtScale(DtScalar x, DtScalar y, DtScalar z);
   An object is referred to by a `DtObjectRef', which is defined as
`void *'.  Any pointer type may be used to refer to an object. In
general, a pointer to a structure in the client application associated
with the collision object should be used.

   An object's motion is specified by changing the placement of the
local coordinate system of the shape.  Initially, the local coordinate
system of an object coincides with the world coordinate system.

   The "current object" is the last created or selected object.  The
placement of the current object is changed, either by translations,
rotations and nonuniform scalings, or by using an OpenGL 4x4
column-major matrix representing an affine transformation.  Placements
are specified absolute or relative to the previous placement.
Rotations are specified using quaternions.  Following example shows how
a pair of objects are given absolute placements.
     dtCreateObject(&object1, hammer);
     dtCreateObject(&object2, nail);
     
     dtSelectObject(&object1);
     dtLoadIdentity();
     dtTranslate(0, 1, 1);
     dtRotate(0, 0, 1, 0);
     
     dtSelectObject(&object2);
     dtLoadIdentity();
     dtTranslate(0, 1, 0);
     dtRotate(0, 0, 0, 1);

Who's Afraid of Quaternions?
----------------------------

   A quaternion is a four-dimensional vector. The set of quaternions of
length one (points on a four-dimensional sphere) map to the set of
orientations in three-dimensional space. Since in many applications an
orientation defined by either a rotation axis and angle or by a triple
of Euler angles is more convenient, the package includes code for
quaternion operations. The code is found in a library of C++ classes for
3D affine transformations. The classes are found in the `include/3D'
directory. All the code is inlined so you do not need to link a library
in order to use the classes.

   The quaternion class is found in the file `Quaternion.h'. The class
has constructors and methods for setting a quaternion. For example
     Quaternion q1(axis, angle);
     Quaternion q2(yaw, pitch, roll);
     
     ...
     
     q1.setRotation(axis, angle);
     q2.setEuler(yaw, pitch, roll);
     
     ...
     
     dtRotate(q1[X], q1[Y], q1[Z], q1[W]);
   Also included is a static method `Quaternion::random()', which
returns a random orientation.

Response Handling
=================

   Collision response in SOLID is handled by means of callback
functions.  The callback functions have the type `DtResponse' defined by
      typedef void (*DtResponse)(
        void *client_data,
        DtObjectRef object1,
        DtObjectRef object2,
        const DtCollData *coll_data)
   Here, `client_data' is a pointer to an arbitrary structure in the
client application, `object1' and `object2' are colliding objects, and
`coll_data' is the response data computed by SOLID.

   Currently, there are three types of response: "simple", "smart" and
"witnessed" response. For simple response the value of `coll_data' is
`NULL'.  For smart and witnessed response `coll_data' points to the
following structure
     typedef struct DtCollData {
       DtVector point1;
       DtVector point2;
       DtVector normal;
     } DtCollData;
   An object of this type represents a pair of points of the respective
objects. The points  `point1' and `point2' are given relative to the
local coordinate system of their respective objects `object1' and
`object2'. The `normal' field is used for smart response only.

   For witnessed response, the points represent a witness of the
collision.  As a result of this the global coordinates of the witness
points are equal.  For smart response, the points represent the closest
point pair of the objects at placements from the previous time frame.
The `normal' field contains the difference of the global coordinates of
the closest point pair, i.e., `normal = Global(point1) -
Global(point2)'.  We will discuss this type of response more thoroughly
further on.

   Response is defined as "default response" for all pairs of objects,
as "object response" for all pairs containing a given object, or as
"pair response" for a particular pair of objects. The commands for
defining and undefining response are
     void dtSetDefaultResponse(DtResponse response, DtResponseType type,
     			  void *client_data)
     void dtClearDefaultResponse()
     
     void dtSetObjectResponse(DtObjectRef obj, DtResponse response,
     			 DtResponseType type, void *client_data)
     void dtClearObjectResponse(DtObjectRef obj)
     void dtResetObjectResponse(DtObjectRef obj)
     
     void dtSetPairResponse(DtObjectRef obj1, DtObjectRef obj2,
     		       DtResponse response, DtResponseType type,
     		       void *client_data)
     void dtClearPairResponse(DtObjectRef obj1, DtObjectRef obj2)
     void dtResetPairResponse(DtObjectRef obj1, DtObjectRef obj2)
   A response is defined by either a `Set' or a `Clear' command.  The
`Clear' command defines the response to be nil (no response).

   Initially, the default response is nil and all pairs of objects have
a default response.  If for an object pair, one of the objects has an
object response defined, then this response overrules the default
response. A pair response overrules any object or default response.  If
for both objects there is an object response defined, then one of the
responses is chosen. In this case, one of the responses may be forced to
be chosen by defining it as a pair response.

   A response is undefined, i.e., reset to a more general setting, by
the `Reset' commands.  The command `dtResetPairResponse' resets the
response of a pair of objects to an object response, if one is defined
for an object in the pair, or otherwise to the default response.  The
command `dtResetObjectResponse' resets the responses of the object
pairs, for which no other object response or a pair response is
defined, to the default response.  Note that whenever an object is
deleted, the object response and all pair responses that are set for
this object are reset automatically.

   The `DtResponseType' is defined by
       typedef enum DtResponseType {
         DT_NO_RESPONSE,
         DT_SIMPLE_RESPONSE,
         DT_SMART_RESPONSE,
         DT_WITNESSED_RESPONSE
       } DtResponseType
   Setting the response type to `DT_NO_RESPONSE' is equivalent to
clearing the response.

   The response callback functions are executed for each colliding pair
of objects by calling
     int dtTest()
   This function returns the number of callback functions that are
executed.

Smart Response
--------------

   For physics-based simulations it is often necessary to have a
representation of the collision plane of a pair of colliding objects in
order to compute the reaction forces.  From a single configuration of
two colliding objects it is hard to compute a collision plane, since
there is no knowledge of how this configuration came about.  Therefore,
SOLID uses the configuration of the objects from the previous time
frame for approximating the collision plane.  If the objects were
disjoint in the previous time frame, then the vector defined by the
difference of the closest point pair of the objects is a good
approximation of the collision plane's normal.

   By selecting smart response for a pair of objects, the closest point
pair and the normal from the previous time frame are computed.  The
points `point1' and `point2' are given in local coordinates and the
`normal' relative to the global basis and pointing away from `object2'.
In order to compute these values, the configuration of objects must be
stored in each time frame. This is done by calling
     void dtProceed();
   Note that in order to guarantee that a non-zero normal can be found,
the `dtProceed' command may only be called if all object pairs for
which a smart response is defined, are disjoint!  The common way of
guarding this is by iteratively doing collision tests and changing the
placements until the objects are disjoint.  Note that it is possible
and often necessary to call `dtTest' multiple times before calling
`dtProceed'.

Deformable Models
=================

   SOLID handles deformations of complex shapes.  In this context
deformations are specified by changes of vertex positions.  Complex
shapes that are defined using a vertex array in the client application
may be deformed by changing the array elements, or specifying a new
array.  SOLID is notified of a change of vertices by the command
     void dtChangeVertexBase(DtShapeRef shape, const void *base);
   When using convex polygons or convex polyhedra as shape components,
the client should warrant that the vertex changes do not violate the
convexity and topology (planar graph embedding) of a component!

   Note that in order to use smart response for deformable shapes, the
change of vertices should be done by specifying a new array.  The
vertex array of the previous time frame should be kept intact,
otherwise SOLID can not determine the configuration of objects of the
previous time frame.  This is best handled by applying a `double
buffering' technique.  After a call to `dtProceed', the new vertex
positions are placed in the free buffer of a pair of vertex buffers,
and `dtChangeVertexBase' is called using this buffer, after which the
other buffer becomes the free buffer.

Caching
=======

   In computer animations there is usually a lot of frame coherence
(objects move smoothly).  In these cases, caching and reusing earlier
computations will yield a considerable performance improvement.  The
"caching" option of SOLID enables an incremental sort on the set of
objects, in order to reduce the number of pairwise intersection tests.
Moreover, when the cashing option is on, data from earlier intersection
tests is stored and used for faster determination of the intersection
status of a pair of objects.  Caching is enabled and disabled by
     void dtEnableCaching()
     void dtDisableCaching()
   Caching may be enabled or disabled at any time during a simulation.
This option is enabled by default.


File: solid2.info,  Node: Projects,  Next: Bugs,  Prev: Usage,  Up: Top

Projects and other things left to do
************************************

Coming Attractions
==================

   Look out for my thesis describing the design and performance
evaluation of SOLID, to appear in March, 1999.


File: solid2.info,  Node: Bugs,  Prev: Projects,  Up: Top

Bug Reports
***********

   Please send remarks, questions and bug reports to gino@win.tue.nl,
or write to Gino van den Bergen, Department of Mathematics and Computing
Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB
Eindhoven, The Netherlands.



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