CS0045 Module 4

Allow applications to render primitives from vertex and vertex state data stored in blocks of memory

Vertex Arrays

Processes the vertices and cache the results for efficient reuse

Vertex Arrays

Version 1.5 introduced the __ __ feature, allowing applications to store data in high-performance server memory

Buffer Object

Suffix: b

Data Type: 8-bit integer

Typical Corresponding C-Language Type: signed char

OpenGL Type Definition: GLbyte

Suffix: s

Data Type: 16-bit integer

Typical Corresponding C-Language Type: signed short

OpenGL Type Definition: GLshort

Suffix: i

Data Type: 32-bit integer

Typical Corresponding C-Language Type: int

OpenGL Type Definition: GLint, GLsizei

Suffix: f

Data Type: 32-bit floating-point

Typical Corresponding C-Language Type: float

OpenGL Type Definition: GLfloat, GLclampf

Suffix: d

Data Type: 64-bit floating-point

Typical Corresponding C-Language Type: double

OpenGL Type Definition: GLdouble, GLclampd

Suffix: ub

Data Type: 8-bit unsigned integer

Typical Corresponding C-Language Type: unsigned char

OpenGL Type Definition: GLubyte

Suffix: us

Data Type: 16-bit unsigned integer

Typical Corresponding C-Language Type: unsigned short

OpenGL Type Definition: GLushort

Suffix: ui

Data Type: 32-bit unsigned integer

Typical Corresponding C-Language Type: unsigned int

OpenGL Type Definition: GLuint, GLenum, GLbitfield

#include <iostream>
#include <GL\glut.h>

using namespace std;

void defaultDisplay();
void point();
void triangle();

int main(int argc, char **argv){
    glutInit(&argc, argv);
    glutInitWindowSize(1024,768);
    glutInitWindowPosition(200,50);
    glutCreateWindow("My First OpenGL");
    glutDisplayFunc(defaultDisplay);
    glutMainLoop();

    return 0;
}

void triangle(){
    glBegin(GL_TRIANGLES);
    glVertex2f(0.0f, .75f);
    glVertex2f(-0.75f, 0.0f);
    glVertex2f(0.75f, 0.0f);
    glEnd();
}

void point(){
    glPointSize(20.0);
    glBegin(GL_POINTS);
    glVertex2f(-0.75f, -0.75f);
    glVertex2f(-0.75f, 0.75f);
    glVertex2f(0.75f, 0.75f);
    glVertex2f(0.75f, -0.75f);
    glEnd();
}

void defaultDisplay(){
    glClear(GL_COLOR_BUFFER_BIT);
    glColor4f(.16f, .72f, .08f, 1.0f);
    point();
    triangle();
    glFlush();
}

Sample Code: Drawing using glBegin() / glEnd()

Conversion to Vertex Array:

void triangle(){
    glBegin(GL_TRIANGLES);
    glVertex2f(0.0f, .75f);
    glVertex2f(-0.75f, 0.0f);
    glVertex2f(0.75f, 0.0f);
    glEnd();
}

void triangle() {

    //1. initialize an array holding vertex coordinates

    GLfloat trianglevertex[] = {
        0.0f, .75f, 0.0f;     /* <---- since we are working with a 2D primitive z axis is always at 0.0  */
        -0.75f, 0.0f, 0.0f;
        0.75f, 0.0f, 0.0f;
    };

    //2. activate and specify pointer to vertex array 
    glEnableClientState(GL_VERTEX_ARRAY);

    //3. specify the pointer to vertex array 
    glVertexPointer(3, GL_FLOAT, 0, trianglevertex);

    //4. execute drawArrays
    glDrawArrays(GL_TRIANGLES,0,3);

    //5. deactivate vertex array after drawing
    glDiasableClientState(GL_VERTEX_ARRAY);
}

void point() {
    glPointSize(20.0);

    GLfloat pointvertex[] = {
        -0.75f, -0.75f, 0.0f; 
        -0.75f, 0.75f, 0.0f;
        0.75f, 0.75f, 0.0f;
        0.75f, -0.75f, 0.0f;
    };

    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3, GL_FLOAT, 0, pointvertex);
    glDrawArrays(GL_POINTS,0,3);
    glDiasableClientState(GL_VERTEX_ARRAY);
}

Conversion to Vertex Array (GL_POINTS)

Define an array of vertex data

glVertexPointer()