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IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL &...

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IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics C / C++ Graphics Programming with Programming with OpenGL & OpenGL & OpenSceneGraph OpenSceneGraph Erik Brisson [email protected]
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Page 1: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

C / C++ Graphics Programming withC / C++ Graphics Programming with OpenGL & OpenSceneGraph OpenGL & OpenSceneGraph

Erik Brisson

[email protected]

Page 2: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

C / C++ Graphics ProgrammingC / C++ Graphics Programming

OpenGL– Program from scratch– Access to all graphics card features– Available on virtually all platforms

OpenSceneGraph– Higher level, built on OpenGL– Program using scene graph paradigm– Lots of utility functions

Page 3: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Tutorial OverviewTutorial Overview

C.G. Paradigm – models, lighting, transforms, etc. OpenGL

– Overview of OpenGL– Window/events (freeglut)– Hands-on

OpenSceneGraph– Overview– Hands-on

Page 4: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Human view of physical worldHuman view of physical world

Page 5: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Human view of imageHuman view of image

Page 6: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Computer graphics paradigmComputer graphics paradigm

Page 7: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

C.G. paradigm with lightC.G. paradigm with light

Page 8: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

C.G. basic calculationC.G. basic calculation

Page 9: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Result is a digital imageResult is a digital image

Page 10: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Resulting imageResulting image

Page 11: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Model geometry – two cuboidsModel geometry – two cuboids

Page 12: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Model geometry - Model geometry - approximationapproximation

Page 13: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Polygonal modelsPolygonal models

Page 14: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Overview: lights, cameras, …Overview: lights, cameras, …

Page 15: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Coordinate SystemsCoordinate Systems

Page 16: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Camera View (Frustum)Camera View (Frustum)

Page 17: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Get examples; build one, build Get examples; build one, build allallLog on to katana

% cp –r /scratch/ogltut .

% cd ogltut

% make ex_green_tri

% ./ex_green_tri

% make all

(note that after tutorial, examples will be available via the web, but not in the location above. Go to http://scv.bu.edu/documentation/presentations/intro_to_Ope

nGL/ogltut )

Page 18: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

ExampleExample

In ex_green_tri.c

void mydraw(void){ glColor3f( 0.0, 1.0, 0.0); glBegin(GL_POLYGON); glVertex3f( 0.0, 0.0, -5.0); glVertex3f( 1.0, 0.0, -5.0); glVertex3f( 1.0, 2.0, -5.0); glEnd();}

Page 19: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

RGB color spaceRGB color space

glColor3f( 0.0, 1.0, 0.0); gives green

Colorsas RGB (red, green, blue)as RGBA (red, green, blue, alpha)

Light is additive, exampleswhite = (1.0, 1.0, 1.0);yellow = (1.0, 1.0, 0.0);

Page 20: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenGL functionsOpenGL functions

% man glColor

void glColor3d( GLdouble red, GLdouble green, GLdouble blue )void glColor3s( GLshort red, GLshort green, GLshort blue )void glColor3ub( GLubyte red, GLubyte green, GLubyte blue )void glColor4d( GLdouble red, GLdouble green, GLdouble blue, GLdouble alpha )

Page 21: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Try this yourself -Try this yourself -

% cp ex_green_tri.c play.c

(A)Make the triangle magenta (purple)solution: soln_magenta_tri.c

(B) Then make it into a rectanglesolution: soln_magenta_rect.c

(C) Then make the vertices different colorssolution: soln_multicolor_rect.c

Page 22: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenGL – primitivesOpenGL – primitives

Page 23: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenGL – primitive exampleOpenGL – primitive example

Let’s look at ex_quad.c

Page 24: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Stepping back: the main loopStepping back: the main loop

int main(int argc, char **argv)

{

int i;

glutInit(&argc, argv);

glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);

glutCreateWindow("ex_quad");

glutDisplayFunc(display);

init();

glutMainLoop();

return 0;

}

Page 25: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

GLUT - The OpenGL Utility Toolkit

Actually, we are using freeglut, a completely OpenSourced alternative to the OpenGL Utility Toolkit (GLUT

Allows creation and management of windows containing OpenGL contexts on a wide range of platforms

Provides event management: read mouse, keyboard and joystick functions.

An 'idle' routine and timers A simple, cascading pop-up menu facility Utility routines to generate various solid and wire frame objects Support for bitmap and stroke fonts Miscellaneous window management functions Freeglut does not require glutMainLoop() !

Page 26: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Example of changes in display()

Run ex_quad_motion

void mydraw(void)

{

static int nframe = 0;

float xoffset;

xoffset = sin((double)nframe/240.0);

drawstuff(xoffset);

nframe++;

}

Page 27: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Better way: OpenGL transformations

void mydraw(void) [ex_translate.c]

{

static float time = 0.0;

float xoffset;

time = glutGet(GLUT_ELAPSED_TIME) / 1000.0;

xoffset = sin((double)(M_PI*time));

glPushMatrix();

glTranslatef(xoffset, 0.0, 0.0);

drawstuff();

glPopMatrix();

glutPostRedisplay();

}

Page 28: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Rotation using OpenGL transform

void mydraw(void) [ex_rotate.c]

{

static float time = 0.0;

float xoffset;

time = glutGet(GLUT_ELAPSED_TIME) / 1000.0;

xoffset = sin((double)(M_PI*time));

glPushMatrix();

glTranslatef(xoffset, 0.0, 0.0);

drawstuff();

glPopMatrix();

glutPostRedisplay();

}

Page 29: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Translation and rotation in 2DTranslation and rotation in 2D

(B) Rotate (B) Rotate by 45 degreesby 45 degrees TranslateTranslate by (7.0, 4.0)by (7.0, 4.0)

(A) Translate(A) Translate by (5.0, 1.0)by (5.0, 1.0)

Page 30: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Composition of transformationsComposition of transformations

Rotate 45 degrees CCW Translate (2, 0) Rotate 45 degrees CCW Translate (2, 0)

Page 31: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Composition of transformationsComposition of transformations

Translate (2, 0) Rotate 45 degrees CCW Translate (2, 0) Rotate 45 degrees CCW

Page 32: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

CompareCompare

Rotate firstRotate firstThen translateThen translate

Translate firstTranslate firstThen rotateThen rotate

Page 33: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Rotations in 3DRotations in 3D

Page 34: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Translations in 3DTranslations in 3DSphereSphere translated bytranslated by (-3.0, 2.0, -4.5)(-3.0, 2.0, -4.5) Blue cubeBlue cube translated bytranslated by (2.0, 0.0, -4.0)(2.0, 0.0, -4.0) rotated 60 degrotated 60 deg around y-axisaround y-axis

Purple cubePurple cube translated bytranslated by (0.0, 0.0, 0.0)(0.0, 0.0, 0.0)

Page 35: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Camera location setupCamera location setupgluLookat(xeye, yeye, zeye, xat, yat, zat, xup, yup, zup)

Page 36: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Camera perspective setupCamera perspective setup

Page 37: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Full view / transform pipeline

Page 38: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Your turnYour turn

Modify ex_lookat.c so that you can so the sphere through the hole in the torus.

Now change it so that “z” is up.

Page 39: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Other transformations - scalingOther transformations - scaling

Page 40: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Multiple transformations

Example in ex_multi_transform.c

Page 41: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Transform Exercise

Modify ex_multi_transform.c so that there are bouncing tetrahedra on all four corners of the platform.

Solution: soln_four_bounce.c

Page 42: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Transform Challenge

Modify ex_rotate.c so strips rotate about the vertical axis going through x=2.0 and z = 0.0

Solution: soln_rotate_challenge.c

Page 43: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Back to lightingBack to lighting

V_eye = P_eye - PV_light = P_light - P

V_eye = (4, 1, 10) - (5, 2, 3) = (-1, -1, 7)V_light = (3, 7, 2) – (5, 2, 3) = (-2, 5, -1)

Page 44: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Unit shading vectorsUnit shading vectors

n = surface normal vectoru_light = unit vector to light pointu_eye = unit vector to view point

Page 45: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

ShadingShadingambient

diffuse

specular

Page 46: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Shading at vertices, Shading at vertices, interpolationinterpolation

Page 47: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Flat shading vs Gouraud Flat shading vs Gouraud shadingshading

Page 48: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

C.G. example - texture mapC.G. example - texture map

Page 49: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Texture map fullTexture map full

++

Page 50: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenGL Helpful MaterialsOpenGL Helpful Materials

http://www.opengl.org http://www.freeglut.org Examples from this tutorial

– http://scv.bu.edu/documentation/presentations/intro_to_OpenGL/ogltut

Examples from opengl.org– http://scv.bu.edu/documentation/presentations/

intro_to_OpenGL/opengl.org_examples/

Many books on OpenGL

Page 51: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenSceneGraphOpenSceneGraph

Open source OpenGL based Similar to SGI Performer Many utility functions

– Notably, 3-D file readers

Page 52: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Get examples; build allGet examples; build all

Log on to katana

% cp –r /scratch/osgtut .

% cd osgtut

% make all

(note that after tutorial, examples will be available via the web, but not in the location above. On the web: http://scv.bu.edu/documentation/presentations/intro_to_OSG/osgtut )

Page 53: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Setting environment variablesSetting environment variables

Instead of using “run_osg” can do this:

% setenv OSG_NOTIFY_LEVEL FATAL

% setenv LD_LIBRARY_PATH \

/usr/local/OpenSceneGraph/lib

% ex_cone

Page 54: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

First osg exampleFirst osg example

Try running: % run_osg ex_simple_viewer cow.obj ex_simple_viewer.cpp // load the nodes from the commandline arguments. osg::Node* model = osgDB::readNodeFile(argv[1]);

// initialize the viewer and set the scene to render osgViewer::Viewer viewer; viewer.setSceneData(model); viewer.setCameraManipulator(new osgGA::TrackballManipulator());

// normal viewer usage. return viewer.run();

Page 55: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

A few improvementsA few improvements

ex_simple_viewer_better.cpp

// tilt the scene to give better default eye position rootnode->setMatrix(osg::Matrix::rotate (osg::inDegrees(30.0f),1.0f,0.0f,0.0f));

// run optimization over the scene graph osgUtil::Optimizer optimzer; optimzer.optimize(rootnode);

Page 56: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Example, making geometryExample, making geometry

ex_cone.cpp // Create a vector to represent the "center of the cone" Vec3 vcen(xcen, ycen, zcen); Cone* cone = new Cone(vcen, radius, height);

// Create a drawable object based on the cone ShapeDrawable *drawable = new ShapeDrawable(cone); drawable->setColor(Vec4(color[0], color[1], color[2], color[3])); Geode* geode = new Geode(); geode->addDrawable(drawable);

Page 57: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Example, combining geometryExample, combining geometry

ex_arrow.cpp

MatrixTransform* arrow = new MatrixTransform;arrow->setMatrix(Matrix::scale(1.0, 1.0, 1.0));arrow->addChild(cone);arrow->addChild(cylinder);

Page 58: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Your turnYour turn

% cp ex_arrow.c play_long_arrow.cpp Modify to make the arrow twice as long % make play_long_arrow Solution: soln_long_arrow.cpp

Page 59: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

A bit more about scaling & transformsA bit more about scaling & transforms

Page 60: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

Solving this scaling problemSolving this scaling problem

ex_vec_arrow.cppmake_vec_arrow(shaft_radius, total_length, r, g, b)

cone_radius = 2*shaft_radius; cone_height = cone_radius; shaft_length = total_length - cone_height; cylinder = make_cylinder(0.0, 0.0, shaft_length/2.0, shaft_radius, shaft_length, r, g, b, 1.0); cone = make_cone(0.0, 0.0, shaft_length + cone_height/4.0, cone_radius, cone_height, r, g, b, 1.0); vec_arrow = new Group; vec_arrow->addChild(cylinder); vec_arrow->addChild(cone);

Page 61: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

ExerciseExercise

% cp ex_vec_arrow.c play_axes.cpp Modify play_axes.cpp to display three unit-length arrows

at the origin – First is RED point in the +X direction– Second is GREEN point in the +Y direction– Third is BLUE point in the +Z direction

% make play_axes.cpp Solution: soln_axes.cpp

Page 62: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

ExerciseExercise

% cp ex_animated_arrow.c play_two_animated_arrows.cpp Modify play_two_animated_arrows.cpp so that the cyan

(blue-green) arrow is tangent to (pointing in) the direction of motion

% make play_two_animated_arrows.cpp Solution: soln_two_animated_arrows.cpp

Page 63: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

““Cloning”Cloning”

ex_twin_arrows.cpp

transform1 = new MatrixTransform(Matrix::translate(2, 2, 0));transform1->addChild(arrow);transform2 = new MatrixTransform(Matrix::translate(-2, -2, 0));transform2->addChild(arrow);rootnode->addChild(transform1);rootnode->addChild(transform2);

Page 64: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

ExerciseExercise

Modify the last example, so that you can animate the PositionAttitudeTransform “arrow” and see what happens …

Solution is left to you

Page 65: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

OpenSceneGraph resourcesOpenSceneGraph resources

http://www.openscenegraph.org– http://www.openscenegraph.org/documentation/

OpenSceneGraphReferenceDocs/

Examples– katana: /usr/local/OpenSceneGraph/examples– http://scv.bu.edu/documentation/presentations/

intro_to_OSG/osgtut

Books– OpenSceneGraph Quick Start Guide– OpenSceneGraph Reference Guides

New book– OpenSceneGraph 3.0: Beginner's Guide

Page 66: IS&T Tutorial: Graphics Prog - OpenGL and OSG C / C++ Graphics Programming with OpenGL & OpenSceneGraph Erik Brisson ebrisson@bu.edu.

IS&T Tutorial: Graphics Prog - OpenGL and OSG

SCV relatedSCV related

Please fill out an online evaluation of this tutorial:

scv.bu.edu/survey/tutorial_evaluation.html

System help

[email protected], [email protected] Web-based tutorials

www.bu.edu/tech/research/tutorials Consultation by appointment

Erik Brisson ([email protected])


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