+++ /dev/null
-\documentclass{article}
-\usepackage{fullpage}
-\usepackage{listings}
-\usepackage{graphicx}
-\begin{document}
-
-\author{Luke Lau}
-\title{CS4052 Assignment 1}
-\maketitle
-
-\lstset{basicstyle=\ttfamily}
-
-\section{Fragment shader colours}
-In order to get the fragment shader to use the position as the colour,
-I had to add an input \texttt{vec4} for the \texttt{vec4 color} that the vertex shader
-outputted. Since the inputs to the fragment shader are from the vertex shader, I had to
-use \texttt{color} and not \texttt{vColor}.
-\lstinputlisting[language=C++]{fragment.glsl}
-\begin{center}
- \includegraphics[width=0.8\textwidth]{part1}
-\end{center}
-
-
-\section{Two triangles}
-
-Two add two triangles, I had to increase the number of vertices drawn to 6
-
-\begin{lstlisting}[language=C++]
-glDrawArrays(GL_TRIANGLES, 0, 6);
-\end{lstlisting}
-
-And add 9 new coordinates and colours for them.
-
-\begin{lstlisting}[language=C++]
-GLfloat vertices[] = {
- 0.0f, -1.0f, 0.0f,
- 1.0f, -1.0f, 0.0f,
- 0.5f, 1.0f, 0.0f,
- -1.0f, -1.0f, 0.0f,
- 0.0f, -1.0f, 0.0f,
- -0.5f, 1.0f, 0.0f
-}
-GLfloat colors[] = {
- 0, 1, 0, 1,
- 1, 0, 0, 1,
- 0, 0, 1, 1,
- 0, 1, 0, 1,
- 1, 0, 0, 1,
- 0, 0, 1, 1
-};
-\end{lstlisting}
-
-\begin{center}
- \includegraphics[width=0.8\textwidth]{part2}
-\end{center}
-
-
-\section{Two triangles, two VAOs and two VBOs}
-
-In order to use two VAOs and two VBOs, I had to combine the VAO setup and the VBO setup
-into one function, since you need to bind the VBO at the time that you create the
-corresponding VAO.
-
-\begin{lstlisting}[language=C++]
-#define BUFFER_OFFSET(i) ((char *)NULL + (i))
-
-GLuint setupBuffers(GLfloat* vertices, GLuint progId) {
-
- GLfloat colors[] = {
- 0, 1, 0, 1,
- 1, 0, 0, 1,
- 0, 0, 1, 1
- };
-
- GLuint numVerts = 3;
-
- GLuint vbo;
- glGenBuffers(1, &vbo);
-
- GLuint vao;
- glGenVertexArrays(1, &vao);
-
- GLuint posId = glGetAttribLocation(progId, "vPosition");
- GLuint colorId = glGetAttribLocation(progId, "vColor");
-
- GLuint vertsLen = numVerts * 3 * sizeof(GLfloat);
- GLuint colorsLen = numVerts * 4 * sizeof(GLfloat);
-
- glBindBuffer(GL_ARRAY_BUFFER, vbo);
- glBufferData(GL_ARRAY_BUFFER, vertsLen + colorsLen, NULL, GL_STATIC_DRAW);
-
- glBufferSubData(GL_ARRAY_BUFFER, 0, vertsLen, vertices);
- glBufferSubData(GL_ARRAY_BUFFER, vertsLen, colorsLen, colors);
-
- glBindVertexArray(vao);
-
- glEnableVertexAttribArray(posId);
- glEnableVertexAttribArray(colorId);
-
- glVertexAttribPointer(posId, 3, GL_FLOAT, GL_FALSE, 0, 0);
- glVertexAttribPointer(colorId, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(numVerts * 3 * sizeof(GLfloat)));
-
- return vao;
-}
-\end{lstlisting}
-
-This could then be used like so:
-\begin{lstlisting}[language=C++]
-GLfloat vertices[2][9] = {
- {
- 0.0f, -1.0f, 0.0f,
- 1.0f, -1.0f, 0.0f,
- 0.5f, 1.0f, 0.0f
- },
-
- {
- -1.0f, -1.0f, 0.0f,
- 0.0f, -1.0f, 0.0f,
- -0.5f, 1.0f, 0.0f
- }
-};
-GLuint* vaos = new GLuint[2];
-vaos[0] = setupBuffers(vertices[0], progId);
-vaos[1] = setupBuffers(vertices[1], progId);
-\end{lstlisting}
-
-When drawing, the VAOs needed to be switched out:
-
-\begin{lstlisting}[language=C++]
-void display() {
- glClear(GL_COLOR_BUFFER_BIT);
- for (int i = 0; i < 2; i++) {
- glBindVertexArray(vaos[i]);
- glDrawArrays(GL_TRIANGLES, 0, 3);
- }
- glutSwapBuffers();
-}
-\end{lstlisting}
-
-\section{Two separate shaders}
-
-I modified the \texttt{compileShaders} function to load in the shader source from a file:
-\begin{lstlisting}[language=C++]
-GLuint compileShaders(char* vertexShader, char* fragmentShader) {
- GLuint progId = glCreateProgram();
-
- attachShader(progId, vertexShader, GL_VERTEX_SHADER);
- attachShader(progId, fragmentShader, GL_FRAGMENT_SHADER);
-
- glLinkProgram(progId);
- GLint success = 0;
- glGetProgramiv(progId, GL_LINK_STATUS, &success);
- if (!success) {
- GLchar log[1024];
- glGetProgramInfoLog(progId, sizeof(log), NULL, log);
- fprintf(stderr, "error linking: %s\n", log);
- exit(1);
- }
-
- return progId;
-}
-\end{lstlisting}
-
-Which meant I could easily swap out the programs used when setting up the buffers:
-
-\begin{lstlisting}[language=C++]
-progIds = new GLuint[2];
-
-GLuint progId1 = compileShaders((char*)"vertex.glsl", (char*)"fragment.glsl");
-vaos[0] = setupBuffers(vertices[0], progId1);
-progIds[0] = progId1;
-validateProgram(progId1);
-
-GLuint progId2 = compileShaders((char*)"vertex.glsl", (char*)"yellow.glsl");
-vaos[1] = setupBuffers(vertices[1], progId2);
-progIds[1] = progId2;
-validateProgram(progId2);
-\end{lstlisting}
-
-The new yellow shader looked like this:
-
-\lstinputlisting[language=C++]{yellow.glsl}
-
-I needed to switch programs during the display function:
-
-\begin{lstlisting}[language=C++]
-void display() {
- glClear(GL_COLOR_BUFFER_BIT);
- for (int i = 0; i < 2; i++) {
- glUseProgram(progIds[i]);
- glBindVertexArray(vaos[i]);
- glDrawArrays(GL_TRIANGLES, 0, 3);
- }
- glutSwapBuffers();
-}
-\end{lstlisting}
-
-\begin{center}
- \includegraphics[width=0.8\textwidth]{part4}
-\end{center}
-
-
-\end{document}
projects / opengl.git / blobdiff