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DESCRIPTION
OpenGL L03-Utilities
Citation preview
Mohammad Shaker
mohammadshaker.com
@ZGTRShaker
2014
OpenGL Graphics
L03 - Utilities
GLU Library Helper Functions
More Draw Functions
• Declare quadric variables first:GLUquadric *quadric = gluNewQudric();
• Now draw what you want:
– Drawing Sphere:
void gluSphere(GLUquadric *qudric, Gldouble radius, GLint slices,
GLint stacks);
– Drawing Cylinder:
void gluCylinder(GLUquadric *qudric,GLdouble baseRadius, GLdouble topRadius,
Gldouble height, GLint slices, GLint stacks);
– Drawing Disk:
void gluDisk(GLUquadric *qudric, GLdouble innerRad, GLdouble outerRad,
GLint slices, GLint loops);
Draw Functions Parameters
• qobj• The quadric object (created with gluNewQuadric).
• radius• The radius of the sphere.
• slices• The number of subdivisions around the z-axis (similar to lines of longitude).
• stacks• The number of subdivisions along the z-axis (similar to lines of latitude).
Draw Functions Parameters
Depth Buffer
Depth Buffer
• Without and with Depth Test enabled:
glDisable(GL_DEPTH_TEST) glEnable(GL_DEPTH_TEST)
Depth Buffer Example
void DrawTriangle(){
rtri+=0.2f;glPushMatrix();glLoadIdentity();glTranslatef(-1.5f,0.0f,-6.0f); glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);glColor3f(1.0f,0.0f,0.0f);glVertex3f( 0.0f, 1.0f, 0.0f); glColor3f(0.0f,1.0f,0.0f);glVertex3f(-1.0f,-1.0f, 0.0f);glColor3f(0.0f,0.0f,1.0f);glVertex3f( 1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
void DrawQuad(){
rquad-=0.15f;glPushMatrix();glLoadIdentity();glTranslatef(1.5f,0.0f,-6.0f)glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);glVertex3f(-1.0f, 1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
int DrawGLScene(GLvoid){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity();
DrawTriangle();DrawQuad();
return TRUE;}
Depth Buffer Example
void DrawTriangle(){
rtri+=0.2f;glPushMatrix();glLoadIdentity();glTranslatef(0f,0.0f,-6.0f); glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);glColor3f(1.0f,0.0f,0.0f);glVertex3f( 0.0f, 1.0f, 0.0f); glColor3f(0.0f,1.0f,0.0f);glVertex3f(-1.0f,-1.0f, 0.0f);glColor3f(0.0f,0.0f,1.0f);glVertex3f( 1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
void DrawQuad(){
rquad-=0.15f;glPushMatrix();glLoadIdentity();glTranslatef(0f,0.0f,-6.0f)glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);glVertex3f(-1.0f, 1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
int DrawGLScene(GLvoid){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity();
DrawTriangle();DrawQuad();
return TRUE;}
Just changed these two lines
Depth Buffer Example
void DrawTriangle(){
rtri+=0.2f;glPushMatrix();glLoadIdentity();glTranslatef(0f,0.0f,-6.0f); glRotatef(rtri, 0, 1, 0);
glBegin(GL_TRIANGLES);glColor3f(1.0f,0.0f,0.0f);glVertex3f( 0.0f, 1.0f, 0.0f); glColor3f(0.0f,1.0f,0.0f);glVertex3f(-1.0f,-1.0f, 0.0f);glColor3f(0.0f,0.0f,1.0f);glVertex3f( 1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
void DrawQuad(){
rquad-=0.15f;glPushMatrix();glLoadIdentity();glTranslatef(0f,0.0f,-6.0f)glRotatef(rquad, 1,0, 0);
glBegin(GL_QUADS);glVertex3f(-1.0f, 1.0f, 0.0f); glVertex3f( 1.0f, 1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f); glEnd();glPopMatrix();
}
int DrawGLScene(GLvoid){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity();
DrawTriangle();DrawQuad();
return TRUE;}
Depth Buffer Example
• Write the following in the DrawGLScene method:– glDisable(GL_DEPTH_TEST);
• Now look at what happened. Without Depth Test, OpenGL will draw the objects
according to their ordering in the code.
With Depth Test Without Depth Test
Handling Input
Handling Input
if (keys[‘C'])
{
//Do Something
}
if(keys[VK_SHIFT])
{
//Do Something
}
Handling Input
if (keys[‘C'])
{
Crouch();
}
if(keys[VK_SHIFT])
{
speed += 0.1f;
}
Using 3D Models
Model and Mesh
Model and Mesh
Model and Bone
Using 3D ModelsYou can use any 3D Model Loader
http://nehe.gamedev.net/tutorial/model_loading/16004/
Using Model_3DS
• You can import and export .3ds files from 3d Design Programs:– 3DS Max
– Maya
– Blender
– Google Sketch
– etc
• You can load and draw .3ds files by using Model_3DS class (or any other):
– Model_3DS.h
– Model_3DS.cpp
• You can garment (texture) 3ds models by using:
– 3Dtexture.h
– 3Dtexture.cpp
Using Model_3DS
• Add the following to the project directory:
– Model_3DS.h
– Model_3DS.cpp
– 3Dtexture.h
– 3Dtexture.cpp
• In Main.cpp– #include “Model_3DS.h”
Using Model_3DS
• Add the following to the project directory:
– Model_3DS.h
– Model_3DS.cpp
– 3Dtexture.h
– 3Dtexture.cpp
• In Main.cpp– #include “Model_3DS.h”
#include “Model_3DS.h”
Model_3DS model;
initGL() {
model = Model_3DS();
model.Load(“ModelFilePath”);
}
DrawGLScene() {
model.Draw();
}
Using Model_3DS
• Add the following to the project directory:
– Model_3DS.h
– Model_3DS.cpp
– 3Dtexture.h
– 3Dtexture.cpp
• In Main.cpp– #include “Model_3DS.h”
#include “Model_3DS.h”
Model_3DS model;
initGL() {
model = Model_3DS();
model.Load(“ModelFilePath”);
model.pos.x = 5;
model.scale= 2;
}
DrawGLScene() {
model.Objects[2].rot.y += 2;
model.Draw();
}
Using Model_3DS
• Add the following to the project directory:
– Model_3DS.h
– Model_3DS.cpp
– 3Dtexture.h
– 3Dtexture.cpp
• In Main.cpp– #include “Model_3DS.h”
#include “Model_3DS.h”
Model_3DS model;
initGL() {
model = Model_3DS();
model.Load(“ModelFilePath”);
model.pos.x = 5;
model.scale= 2;
}
DrawGLScene() {
model.Objects[2].rot.y += 2;
model.Draw();
}
You can control each mesh separately
Fog
Why using Fog?
Why using Fog?It’s cool!
Why using Fog?And it can Hide a “Close” Far Clipping Plane
Fog
glFog(property, value)
• Depth Cueing
– Specify a range for a linear fog ramp
• GL_FOG_LINEAR
• Environmental effects
– Simulate more realistic fog
• GL_FOG_EXP
• GL_FOG_EXP2
Fog
Displaying Text
Displaying Text
• “glutFont.h”
• “glutFont.cpp”
• DrawGLScene()
glPushMatrix( );
glTranslatef(0,-1.2,0);
DisplayString(0,0,GLUT_BITMAP_HELVETICA_18,“Hello, How are you?");
glPopMatrix( );
Collision Detection
Collision Detection
Collision Detection
• Approximation
Collision Detection
• Approximation
Collision Detection
• Approximation
Collision Detection
• Approximation
When to use What?
Collision Detection
• Approximation
A better way to combine both approaches
Collision DetectionHierarchical Modeling
Collision Detection
Collision Detection
Collision Detection
Collision DetectionIn hierarchical model you would use both the large
sphere, and the small spheres.
Collision DetectionQuad Tree Approach
Picking Objects in 3D Scene
Picking with Ghoscherhttp://ghoscher.me/2010/11/25/xna-picking-tutorial-part-i
Picking with Ghoscherhttp://ghoscher.me/2010/11/25/xna-picking-tutorial-part-i
Picking
• The picking region is usually specified in a piece of code like this:glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPickMatrix(x, y, width, height, viewport);
• The picking matrix is the rare situation where the standard projection matrix
(perspective or ortho) is multiplied onto a non-identity matrix.
• Each hit record contains:
• number of names per hit
• smallest and largest depth values
• all the names
Picking
• Programming steps
– Restrict “drawing” to small region near pointer
Use glupickmatrix() on projection matrix
– Enter selection mode; re-render scene
– Primitives drawn near cursor cause hits
– Exit selection; analyze hit records
Picking with Ray Castinghttp://antongerdelan.net/opengl/raycasting.html
Now why spheres?
Now why spheres?Hitting the body’s bounding sphere is easier and faster!
Lens Flarehttp://nehe.gamedev.net/tutorial/3d_lens_flare_with_occlusion_testing/16007/
Lens Flare
How to?
Lens FlareUsing Projection Matrix
Lens Flare – Using Projection Matrix
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