© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Chapter 4 – Object Manipulation in VRML

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Understanding Coordinate System  VRML defines the unit of measure of the world coordinate system to be metres  All other coordinate systems are built from transformations based from the world coordinate system  The VRML convention that one unit equals one meter  In VRML, we can create any number of coordinate systems

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Understanding Coordinate System  Each new coordinate system is positioned or translated relative to the origin of another coordinate system  When a new coordinate system is relative to another, we say that the new coordinate system is a child coordinate system that is nested within the within the parent coordinate system  The entire family tree of coordinate systems including any shape we build within those coordinate system is called the scene graph

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Understanding Coordinate System  Try to visualize the coordinate system as indicated in the diagram below

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Understanding Coordinate System  The ability to create coordinate systems is a very powerful feature of VRML  Consider the steps in placing the lamp on the table while the table is inside a room  We need to perform the following steps:  Create a lamp, building each of its components relative to a lamp coordinate system  Create a table, building each of its components relative to a table coordinate system

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Understanding Coordinate System  Place the lamp on the table by positioning the lamp coordinate system relative to the table coordinate system  Now the lamp coordinate system is a child of the table coordinate system  Create a room, building each of its components relative to a room coordinate system  Place the table (and its lamp) by positioning the table coordinate system relative to the room coordinate system

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Grouping Coordinate Systems  We need to use a Transform node to create a new coordinate system and specify the position or translation relative to a parent coordinate system  The Transform node is similar to the Group node in that it contains a list of child nodes  These child nodes could be Shape node, Group node or Transform nodes  All of the child nodes are built at the origin within the Transform node’s coordinate system

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Grouping Coordinate Systems  All of the child nodes are built at the origin within the Transform node’s coordinate system  If the position of that node changes, all its child nodes will change accordingly with the changed coordinate system  Like Shape and Group nodes, the Transform node may be the child of a parent Group or Transform node

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Grouping Coordinate Systems  The coordinate system of the parent node is the parent coordinate system of the Transform node coordinate system  If the root node is a Transform node, then the parent coordinate system is the world coordinate system of the VRML file

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING The Transform Node  The Transform node creates a new coordinate system relative to its parent node coordinate system Transform { children [ ]# exposedField MFNode translation # exposedFieldSFVec3f rotation # exposedFieldSFRotation scale # exposedFieldSFVec3f scaleOrientation # exposedFieldSFRotation bboxCenter # fieldSFVec3f bboxSize # fieldSFVec3f center # exposedFieldSFVec3f addChildren# eventInMFNode removeChildren# eventOutMFNode }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING The Transform Node  The value of the children exposed field specifies a list of child nodes to be included in the group  Typical values in the children are the Shape nodes, Group nodes and Transform nodes  The value of the translation exposed field specify the distances in X, Y, Z directions  The value of the translation exposed field can be changed by routing an event to the exposed field’s implied set_translation eventIn.  When the event is received, the translation field is set and the new translation is sent using the exposed field’s implied translation_changed eventOut.

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating 2.0 units along x-axis and building Cylinder #VRML V2.0 utf8 Transform { translation children [ Shape { appearance Appearance { material Material { } } geometry Cylinder { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating -2.0 units along x-axis and building Cylinder #VRML V2.0 utf8 Transform { translation children [ Shape { appearance Appearance { material Material { } } geometry Cylinder { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating 2.0 units along y-axis and building Cylinder #VRML V2.0 utf8 Transform { translation children [ Shape { appearance Appearance { material Material { } } geometry Cylinder { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating 2.0 units along z-axis and building Cylinder #VRML V2.0 utf8 Transform { translation children [ Shape { appearance Appearance { material Material { } } geometry Cylinder { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating along x-, y-, z-axis and building Cylinder #VRML V2.0 utf8 Transform { translation children [ Shape { appearance Appearance { material Material { } } geometry Cylinder { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Building Shapes in Multiple Coordinate Systems #VRML V2.0 utf8 Group { children [ # Draw the hut walls Shape { appearance DEF White Appearance { material Material { } } geometry Cylinder { height 2.0 radius 2.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Building Shapes in Multiple Coordinate Systems # Draw the hut roof Transform { translation children [ Shape { appearance USE White geometry Cone { height 2.0 bottomRadius 2.5 } ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Coordinate Systems #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Coordinate Systems # Left Column Transform { translation children Shape { appearance USE White geometry Cylinder { radius 0.3 height 6.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Coordinate Systems # Right Column Transform { translation children Shape { appearance USE White geometry Cylinder { radius 0.3 height 6.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Coordinate Systems # Archway span Transform { translation children Shape { appearance USE White geometry Box { size } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Coordinate Systems #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Coordinate Systems # First archway # Left Column DEF LeftColumn Transform { translation children DEF Column Shape { appearance USE White geometry Cylinder { radius 0.3 height 6.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Coordinate Systems # Right Column DEF RightColumn Transform { translation children USE Column }, # Archway span DEF ArchwaySpan Transform { translation children Shape { appearance USE White geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Coordinate Systems # Second archway Transform { translation children [ USE LeftColumn, USE RightColumn, USE ArchwaySpan ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating Shapes  In order to make the object more realistic, we must also control the orientation or rotation using the rotation field of the Transform node  A rotation axis is an imaginary line about which a coordinate system in rotated  A rotation axis can point to any direction in space  In order to specify a direction for a rotation axis, one could imagine drawing a line between two coordinates in space

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating Shapes  Usually, one coordinate corresponds to the origin. Therefore in specifying a rotation axis, (0, 1.0, 0) and (0, 2.0, 0) are all equivalent as they all point upwards  In addition to specifying a rotation axis, we must also indicate how much we want the new coordinate system to rotate about that axis and this value is measured in radian  By default, the centre of rotation is the origin of that coordinate system

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating Shapes  Using the Transform node, we could specify the 3D coordinates for rotation centre within a new coordinate system Transform { children [ ]# exposedField MFNode translation # exposedFieldSFVec3f rotation # exposedFieldSFRotation scale # exposedFieldSFVec3f scaleOrientation # exposedFieldSFRotation bboxCenter # fieldSFVec3f bboxSize # fieldSFVec3f center # exposedFieldSFVec3f addChildren# eventInMFNode removeChildren# eventOutMFNode }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating Shapes  The values of the rotation exposed field specify a rotation axis about which the new coordinate system and a rotation angle, measured in radian  The rotation exposed field value can be changed by routing an event to the exposed field’s implied set_rotation eventIn.  When the event is received, the rotation field is set and the new rotation is sent using the exposed field’s implied rotation_changed eventOut

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating in Different Direction #VRML V2.0 utf8 Transform { rotation children [ Shape { appearance Appearance { material Material { } } geometry Box { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating in Different Direction #VRML V2.0 utf8 Transform { rotation children [ Shape { appearance Appearance { material Material { } } geometry Box { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating in Different Direction #VRML V2.0 utf8 Transform { rotation children [ Shape { appearance Appearance { material Material { } } geometry Box { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating in Different Direction #VRML V2.0 utf8 Transform { rotation children [ Shape { appearance Appearance { material Material { } } geometry Box { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Rotated Coordinate Systems #VRML V2.0 utf8 Group { children [ # Arm 1 DEF Arm1 Shape { appearance Appearance { material Material { } } geometry Cylinder { height 1.0 radius 0.1 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Rotated Coordinate Systems # Arm 2 Transform { rotation children USE Arm1 }, # Arm 3 Transform { rotation children USE Arm1 } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Rotated Coordinate Systems #VRML V2.0 utf8 Group { children [ # Arm 1 DEF Arm1 Shape { appearance Appearance { material Material { } } geometry Cylinder { height 1.0 radius 0.1 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Rotated Coordinate Systems # Arm 2 DEF Arm2 Transform { rotation children USE Arm1 }, # Arm 3 DEF Arm3 Transform { rotation children USE Arm1 },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Rotated Coordinate Systems # Arms 4 and 5 Transform { rotation children [ USE Arm2, USE Arm3 ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Rotating Coordinate Systems #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Rotating Coordinate Systems # First archway # Left Column DEF LeftColumn Transform { translation children DEF Column Shape { appearance USE White geometry Cylinder { radius 0.3 height 6.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Rotating Coordinate Systems # Right Column DEF RightColumn Transform { translation children USE Column }, # Archway span DEF ArchwaySpan Transform { translation children Shape { appearance USE White geometry Box{ size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Rotating Coordinate Systems # Left Roof DEF LeftRoof Transform { translation rotation children DEF Roof Shape { appearance USE White geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Rotating Coordinate Systems # Right Roof DEF LeftRoof Transform { translation rotation children USE Roof } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating about a Center Point #VRML V2.0 utf8 Group{ children [ # Lamp base Shape { appearance DEF White Appearance { material Material { } } geometry Cylinder { radius 0.1 height 0.01 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Rotating about a Center Point # Base joint Transform { translation rotation center children [ # Lower arm Shape { appearance USE White geometry Cylinder { radius 0.01 height 0.3 } ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling Shapes  VRML also enables us to scale a coordinate system, increasing or decreasing the size relative to a parent coordinate system  Shapes created within the scaled coordinate system are built at the new scale of the coordinate system  By scaling coordinate systems, we can enlarge or shrink shapes or groups of shapes  A scale factor is used in scaling and this scale factor is a multiplication factor.  If the value of this scale factor is 0.5, then the original object will shrink in size by half

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling Shapes  The Transform node’s scale field uses three scale factors, one along the x-axis, one along the y-axis and one along the z-axis  By default, the centre of scaling is the original of that coordinate system  Now we could make use of the combination of translation, rotation and scaling within the same Transform node to achieve the effect that we want  The value of the scale exposed field specify the scale factors in the X, Y and Z directions for the new coordinate system

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling Shapes  All the scale factors have to be a positive value  Values between 0.0 and 1.0 would imply reduction and values above 1.0 would imply expansion  The value of the scaleOrientation field specify a rotation axis and angle which to rotate the new coordinate system prior to scaling, and then unrotate if after scaling  Like the rotation field, the first values specify the X, Y and Z components of a 3D coordinate in the new, translated coordinate system and last value specifies the rotation angle measured in radian

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling in Different Direction #VRML V2.0 utf8 Transform { scale children [ Shape { appearance Appearance { material Material { } } geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling in Different Direction #VRML V2.0 utf8 Transform { scale children [ Shape { appearance Appearance { material Material { } } geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling in Different Direction #VRML V2.0 utf8 Transform { scale children [ Shape { appearance Appearance { material Material { } } geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling in Different Direction #VRML V2.0 utf8 Transform { scale children [ Shape { appearance Appearance { material Material { } } geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling in Different Direction #VRML V2.0 utf8 Transform { scale children [ Shape { appearance Appearance { material Material { } } geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Scale Coordinate Systems #VRML V2.0 utf8 Group { children [ # Wing Transform { scale children Shape { appearance DEF White Appearance { material Material { } } geometry Cylinder { radius 1.0 height } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Constructing Multiple Scaled Coordinate Systems # Fuselage Transform { scale children Shape { appearance USE White geometry Sphere { } } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Scaled Coordinate Systems #VRML V2.0 utf8 Group { children [ # Wing DEF Wing Transform { scale children Shape { appearance DEF White Appearance { material Material { } } geometry Cylinder { radius 1.0 height } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Scaled Coordinate Systems # Fuselage DEF Fusalage Transform { scale children Shape { appearance USE White geometry Sphere { } } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Nesting Scaled Coordinate Systems # Wing detail and fusalage dome Transform { scale children [ USE Wing, USE Fusalage ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems # First archway DEF Archway Group { children [ # Left Column DEF LeftColumn Transform { translation children DEF Column Shape { appearance USE White geometry Cylinder { radius 0.3 height 6.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems # Right Column DEF RightColumn Transform { translation children USE Column }, # Archway span DEF ArchwaySpan Transform { translation children Shape { appearance USE White geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems # Left Roof DEF LeftRoof Transform { translation rotation children DEF Roof Shape { appearance USE White geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems # Right Roof DEF RightRoof Transform { translation rotation children USE Roof } ] }, # Left small archway Transform { translation scale children USE Archway },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Translating and Scaling Coordinate Systems # Right small archway Transform { translation scale children USE Archway } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling about a Center Point #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling about a Center Point # Tree Transform { translation scale center children [ # Trunk Shape { appearance USE White geometry Cylinder { radius 0.5 height 2.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Scaling about a Center Point # Branches Transform { translation children Shape { appearance USE White geometry Cone { bottomRadius 2.0 height 4.0 } ] } ] }

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Using a Scale Orientation #VRML V2.0 utf8 Group { children [ # Ground Shape { appearance DEF White Appearance { material Material { } } geometry Box { size } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Using a Scale Orientation # Tree Transform { translation scale scaleOrientation center children [ # Trunk Shape { appearance USE White geometry Cylinder { radius 0.5 height 2.0 } },

© TMC Computer School HC20203 VRML HIGHER DIPLOMA IN COMPUTING Using a Scale Orientation # Branches Transform { translation children Shape { appearance USE White geometry Cone { bottomRadius 2.0 height 4.0 } ] } ] }