Vertex buffer object

The following functions form the core of VBO access and manipulation:

In OpenGL 1.4:

glGenBuffersARB(sizei n, uint *buffers)

Generates a new VBO and returns its ID number as an unsigned integer. Id 0 is reserved.

glBindBufferARB(enum target, uint buffer)

Use a previously created buffer as the active VBO.

glBufferDataARB(enum target, sizeiptrARB size, const void *data, enum usage)

Upload data to the active VBO.

glDeleteBuffersARB(sizei n, const uint *buffers)

Deletes the specified number of VBOs from the supplied array or VBO id.

In OpenGL 2.1, OpenGL 3.x and OpenGL 4.x:

glGenBuffers(sizei n, uint *buffers)

Generates a new VBO and returns its ID number as an unsigned integer. Id 0 is reserved.

glBindBuffer(enum target, uint buffer)

Use a previously created buffer as the active VBO.

glBufferData(enum target, sizeiptrARB size, const void *data, enum usage)

Upload data to the active VBO.

glDeleteBuffers(sizei n, const uint *buffers)

Deletes the specified number of VBOs from the supplied array or VBO id.

In C, using OpenGL 2.1

//Initialise VBO - do only once, at start of program //Create a variable to hold the VBO identifier GLuint triangleVBO; //Vertices of a triangle (counter-clockwise winding) float data[] = {1.0, 0.0, 1.0, 0.0, 0.0, -1.0, -1.0, 0.0, 1.0}; //try float data[] = {0.0, 1.0, 0.0, -1.0, -1.0, 0.0, 1.0, -1.0, 0.0}; if the above doesn't work. //Create a new VBO and use the variable id to store the VBO id glGenBuffers(1, &triangleVBO); //Make the new VBO active glBindBuffer(GL_ARRAY_BUFFER, triangleVBO); //Upload vertex data to the video device glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW); //Make the new VBO active. Repeat here in case it has changed since initialisation glBindBuffer(GL_ARRAY_BUFFER, triangleVBO); //Draw Triangle from VBO - do each time window, view point or data changes //Establish its 3 coordinates per vertex with zero stride in this array; necessary here glVertexPointer(3, GL_FLOAT, 0, NULL); //Establish array contains vertices (not normals, colours, texture coords etc) glEnableClientState(GL_VERTEX_ARRAY); //Actually draw the triangle, giving the number of vertices provided glDrawArrays(GL_TRIANGLES, 0, sizeof(data) / sizeof(float) / 3); //Force display to be drawn now glFlush();

In C, using OpenGL 3.x and OpenGL 4.x

Vertex Shader:

/*----------------- "exampleVertexShader.vert" -----------------*/ #version 150 // Specify which version of GLSL we are using. // in_Position was bound to attribute index 0("shaderAttribute") in vec3 in_Position; void main() { gl_Position = vec4(in_Position.x, in_Position.y, in_Position.z, 1.0); } /*--------------------------------------------------------------*/

Fragment Shader:

/*---------------- "exampleFragmentShader.frag" ----------------*/ #version 150 // Specify which version of GLSL we are using. precision highp float; // Video card drivers require this line to function properly out vec4 fragColor; void main() { fragColor = vec4(1.0,1.0,1.0,1.0); //Set colour of each fragment to WHITE } /*--------------------------------------------------------------*/

Main OpenGL Program:

/*--------------------- Main OpenGL Program ---------------------*/ /* Create a variable to hold the VBO identifier */ GLuint triangleVBO; /* This is a handle to the shader program */ GLuint shaderProgram; /* These pointers will receive the contents of our shader source code files */ GLchar *vertexSource, *fragmentSource; /* These are handles used to reference the shaders */ GLuint vertexShader, fragmentShader; const unsigned int shaderAttribute = 0; /* Vertices of a triangle (counter-clockwise winding) */ float data[3][3] = { { 0.0, 1.0, 0.0 }, { -1.0, -1.0, 0.0 }, { 1.0, -1.0, 0.0 } }; /*---------------------- Initialise VBO - (Note: do only once, at start of program) ---------------------*/ /* Create a new VBO and use the variable "triangleVBO" to store the VBO id */ glGenBuffers(1, &triangleVBO); /* Make the new VBO active */ glBindBuffer(GL_ARRAY_BUFFER, triangleVBO); /* Upload vertex data to the video device */ glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_STATIC_DRAW); /* Specify that our coordinate data is going into attribute index 0(shaderAttribute), and contains three floats per vertex */ glVertexAttribPointer(shaderAttribute, 3, GL_FLOAT, GL_FALSE, 0, 0); /* Enable attribute index 0(shaderAttribute) as being used */ glEnableVertexAttribArray(shaderAttribute); /* Make the new VBO active. */ glBindBuffer(GL_ARRAY_BUFFER, triangleVBO); /*-------------------------------------------------------------------------------------------------------*/ /*--------------------- Load Vertex and Fragment shaders from files and compile them --------------------*/ /* Read our shaders into the appropriate buffers */ vertexSource = filetobuf("exampleVertexShader.vert"); fragmentSource = filetobuf("exampleFragmentShader.frag"); /* Assign our handles a "name" to new shader objects */ vertexShader = glCreateShader(GL_VERTEX_SHADER); fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); /* Associate the source code buffers with each handle */ glShaderSource(vertexShader, 1, (const GLchar**)&vertexSource, 0); glShaderSource(fragmentShader, 1, (const GLchar**)&fragmentSource, 0); /* Free the temporary allocated memory */ free(vertexSource); free(fragmentSource); /* Compile our shader objects */ glCompileShader(vertexShader); glCompileShader(fragmentShader); /*-------------------------------------------------------------------------------------------------------*/ /*-------------------- Create shader program, attach shaders to it and then link it ---------------------*/ /* Assign our program handle a "name" */ shaderProgram = glCreateProgram(); /* Attach our shaders to our program */ glAttachShader(shaderProgram, vertexShader); glAttachShader(shaderProgram, fragmentShader); /* Bind attribute index 0 (shaderAttribute) to in_Position*/ /* "in_Position" will represent "data" array's contents in the vertex shader */ glBindAttribLocation(shaderProgram, shaderAttribute, "in_Position"); /* Link shader program*/ glLinkProgram(shaderProgram); /*-------------------------------------------------------------------------------------------------------*/ /* Set shader program as being actively used */ glUseProgram(shaderProgram); /* Set background colour to BLACK */ glClearColor(0.0, 0.0, 0.0, 1.0); /* Clear background with BLACK colour */ glClear(GL_COLOR_BUFFER_BIT); /* Actually draw the triangle, giving the number of vertices provided by invoke glDrawArrays while telling that our data is a triangle and we want to draw 0-3 vertexes */ glDrawArrays(GL_TRIANGLES, 0, (sizeof(data) / 3) / sizeof(GLfloat)); /*---------------------------------------------------------------*/