Intro to VRML Let s build something

Intro to VRML • Let’s build something! • The source code examples in this tutorial WORK!

VRML File Structure • Files start with a special comment – Gives version number, and character coding in the file #VRML V 2. 0 utf 8 World. Info { title “This is an example” info ["(C) Copyright 2012 someone special"] } DEF FBOX Shape { appearance Appearance { material Material { } } geometry Box { } }

VRML File Structure • World Info – Title of file, can be rendered by VRML viewers • Objects – Contents of the world #VRML V 2. 0 utf 8 World. Info { title “This is an example” info ["(C) Copyright 2012 someone special"] } DEF FBOX Shape { appearance Appearance { material Material { } } geometry Box { } }

Shape node Objects appearance field Shape { appearance Appearance { material Material { } } geometry Box { } } geometry field Shape node: A data structure containing two fields for describing an object. Causes a shape to be rendered.

Giving Objects Names • The shape object now has a name, FBOX. DEF FBOX Shape { appearance Appearance { material Material { } } geometry Box { } } • VRML is case sensitive.

Transformations • Translation – Moving an object to a new (x, y, z) coordinate – In VRML, center of object is moved by adding x, y, z changes • Rotation – Rotate object along one or more of the (x, y, z) coordinates by an amount of radians (an angle) • Scaling – Alter size of an object in one of three possible ways: along the x-coordinate, the y-coordinate, and/or z-coordinate – In VRML, scaling is applied by giving three scale factors: (Sx, Sy, Sz) • E. g. , (2, 2, 2) will double the size of an object, where as (1, 2, 3) will leave the x-coordinate unchanged, double scale of the object along the y-coordinate dimension, and triple the size of the object along the zcoordinate dimension

Coordinate System

Transform Nodes Transform node Scale by x=2, y= 0. 5, z=2 Transform { scale 2 0. 5 2 rotation 0 1 0 0. 78 translation 0 -1. 5 0 children [ USE FBOX ] } Rotate by. 78 radians (45 degrees) along y coordinate Don’t change x-coord, subtract 1. 5 from y, and don’t change z Transform node: A data structure giving rotations, translations, and scaling for an object. Operations carried out in sequence given, top to bottom. Transformations within a transform apply to the children of a node. Causes a transformed shape to be rendered.

Example 2 • Transform adds a second object • Places it below first one • Applies the given changes to second object Transform node #VRML V 2. 0 utf 8 DEF FBOX Shape { appearance Appearance { material Material { } } geometry Box { } } Transform { scale 2 0. 5 2 rotation 0 1 0 0. 78 translation 0 -1. 5 0 children [ USE FBOX ] }

Appearance nodes DEF FBOX Shape { appearance Appearance { material Material { } } geometry Box { } } • Can contain a material node or a texture node • Material nodes can contain six fields: – diffuse. Color: RGB color values, R, G, B between 0 and 1 • normal color of object – specular. Color: color values • color of highlights on shiny objects – emissive. Color: color values • object 'glows' with a light of its own of this color • doesn't cast light on other objects – ambient. Intensity: number between 0 and 1 • amount of ambient light that object reflects – shininess: number between 0 and 1 • How reflective the object is – transparency: number between 0 and 1 • How transparent the object is • Some VRML browsers will not support partly-transparent objects.

Example Shape { appearance Appearance { material Material { emissive. Color 0 0. 8 0 transparency 0. 5 } } geometry Box { } } • Glowing transparent green • Transparency of 1 means invisible; 0 means no transparency (default)

Texture nodes • Image. Texture – Cover an object with a still image – Specified as a JPEG or PNG file • Movie. Texture – Texture-maps an MPEG file onto an object • Pixel. Texture – Define your own textures via RGB or grayscale

#VRML V 2. 0 utf 8 #brickwall. wrl # demonstrates use of textures Shape { appearance DEF the. Texture Appearance { texture Image. Texture { url ["brick. jpg"] } # end texture } # end appearance geometry Box { size 1 2 3 } # end geometry } # end shape

More on Geometry Nodes • Box – Specified with X, Y, Z sizes • Cylinder – Radius, height, and flags controlling rendering of ends, and side • Sphere – Specified with radius • Cone – Bottom radius, and height, and flags controlling rendering of bottom & side • Text geometry Box { size 5. 5 3. 75 1. 0 } geometry Cylinder { radius 0. 5 height 10 top FALSE } geometry Sphere { radius 10, 000 } geometry Cone { bottom. Radius 5 height 10 bottom FALSE }

Flags for cylinder • There also three other fields, side, top, and bottom. • These are Boolean values (TRUE or FALSE), and tell the browser whether to display the appropriate section of the cylinder. • These default to TRUE, so you don't need to put them in at all most of the time. However, if you had a cylinder where an end was obscured by another object, it would be worth turning off that end, as it will reduce the amount of work for the browser, speeding up the execution of your world.

Prototypes: More on Code Reuse • So far, our statements have always resulted in rendered images in the VRML viewer • It is useful to specify graphical procedures that just declare shapes, and don’t render them • Parameters to these graphical procedures are also useful • One way to create procedures in VRML is through the PROTO (prototype) statement

PROTO Syntax PROTO <Prototype. Name> [ <Parameter Descriptions> ## syntax: ## field <parameter-type> <param-name> <defaults> ] { <Graphical Description> }

PROTO Parameter Types • • • SFBool – This is a single boolean value, which can take the value "TRUE" or "FALSE". SFColor & MFColor – SFColor is a field containing a single color, made up of three floating-point numbers between 0 and 1 corresponding to the red, green and blue values of that color, e. g. 0 1 0 is green. MFColor is a field containing multiple colors, e. g. [0 1 0, 1 0 0, 0 0 1]. SFFloat & MFFloat – SFFloat is a single floating-point value, e. g. 7. 5. And MFFloat is a number of floatingpoint values, e. g. [1. 0, 3. 4, 76. 54]. SFImage – SFImage is a two-dimensional image, either in colour or grey. It consists of: • Two integers, representing the width and height of the image. • One integer representing the number of components in the image. 1 is grey levels only, 2 is grays with transparency, 3 is RGB color, and 4 is RGB with transparency. – After these, there are width * height hexadecimal numbers, consisting of 2 digits for each component. So, 0 x. FF would be white in a 1 -component image, and 0 x. FF 00007 F would be half-transparent red in a 4 -component image. – Pixels are specified from left to right, bottom to top. SFInt 32 & MFInt 32 – A single or list of 32 -bit integer numbers. These can be in decimal or hexadecimal format. Hexadecimal numbers start with 0 x, e. g. 0 x. FF is 255 in decimal.

PROTO Parameter Types • SFNode & MFNode – • SFRotation & MFRotation – • A single or list of times. Times are specified as floating-point numbers representing the number of seconds elapsed since midnight on the 1 st January 1970. This make more sense when we cover events later on. SFVec 2 f & MFVec 2 f – • This type contains a list of characters in the utf-8 character set. ASCII is a subset of utf-8, so you needn't worry about different character sets or anything. A string (SFString) is specified as "Hello", in double quotes. A list (MFString) looks like this: ["Hello", "World"]. SFTime & MFTime – • These fields specify a rotation about an axis. It is made up of four floating-point numbers. The first three specify X Y and Z coordinates for the vector corresponding to the axis about which to rotate, and the fourth is the number of radians to rotate by. SFString & MFString – • SFNode is a single node, and MFNode is a list of nodes. Note that the children field in many nodes is of type MFNode. A single or list of 2 D vectors. A 2 D vector is a pair of floating-point numbers. SFVec 3 f & MFVec 3 f – A single or list of 3 D vectors. A 3 D vector is a triple of floating-point numbers.

Example Prototype: For Defining Graph Axes PROTO graph. Axis [ field SFVec 3 f dimensions 0 0 0 ] { Shape { appearance Appearance { material Material { } } geometry Box { size IS dimensions } } } • Defines a graphical procedure (prototype) called graph. Axis • Procedure has a formal parameter called dimensions, which is a vector of 3 floats • Parameter used with “IS” syntax

Problem • Define a prototype for a plot point with parameters for color and position

PROTO plot. Point [ field SFVec 3 f position 0 0 0 field SFColor color 1 1 1 ] { Transform { translation IS position children [ Shape { appearance Appearance { material Material { diffuse. Color IS color } } geometry Sphere { radius. 1 } } ] } } Solution

Navigation Is supposed to work as in HTML Anchor { children [ USE HEAD ] description "Back to the ITU Home Page" url “http: //www. itu. edu" }

Practice • Make a spaceship! • Make a house? Something?