From 6cbf05fce9821efdbbb141c6a0dbff6e6745fbc0 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Tue, 18 Sep 2018 11:09:23 +0100
Subject: [PATCH] Add yellow shader

---
 assignment1.cpp | 78 ++++++++++++++++++++++++++++---------------------
 yellow.glsl     |  5 ++++
 2 files changed, 50 insertions(+), 33 deletions(-)
 create mode 100644 yellow.glsl

diff --git a/assignment1.cpp b/assignment1.cpp
index fd55f4e..b3049f0 100644
--- a/assignment1.cpp
+++ b/assignment1.cpp
@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <fstream>
 #include <sstream>
+#include <vector>
 #ifdef __APPLE__
 #include <GL/glew.h>
 #else
@@ -14,10 +15,12 @@
 using namespace std;
 
 GLuint* vaos;
+GLuint* progIds;
 
 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);
 	}
@@ -50,11 +53,11 @@ void attachShader(GLuint progId, const char* filePath, GLenum type) {
 	glAttachShader(progId, shader);
 }
 
-GLuint compileShaders() {
+GLuint compileShaders(char* vertexShader, char* fragmentShader) {
 	GLuint progId = glCreateProgram();
 
-	attachShader(progId, "vertex.glsl", GL_VERTEX_SHADER);
-	attachShader(progId, "fragment.glsl", GL_FRAGMENT_SHADER);
+	attachShader(progId, vertexShader, GL_VERTEX_SHADER);
+	attachShader(progId, fragmentShader, GL_FRAGMENT_SHADER);
 
 	glLinkProgram(progId);
 	GLint success = 0;
@@ -66,26 +69,12 @@ GLuint compileShaders() {
 		exit(1);
 	}
 
-	glUseProgram(progId);
 	return progId;
 }
 
 #define BUFFER_OFFSET(i) ((char *)NULL + (i))
 
-GLuint* setupBuffers(GLuint progId) {
-	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 setupBuffers(GLfloat* vertices, GLuint progId) {
 
 	GLfloat colors[] = {
 		0, 1, 0, 1,
@@ -95,11 +84,11 @@ GLuint* setupBuffers(GLuint progId) {
 
 	GLuint numVerts = 3;
 
-	GLuint vbos[2];
-	glGenBuffers(2, vbos);
+	GLuint vbo;
+	glGenBuffers(1, &vbo);
 
-	GLuint* vaos = new GLuint[2];
-	glGenVertexArrays(2, vaos);
+	GLuint vao;
+	glGenVertexArrays(1, &vao);
 
 	GLuint posId = glGetAttribLocation(progId, "vPosition");
 	GLuint colorId = glGetAttribLocation(progId, "vColor");
@@ -107,30 +96,24 @@ GLuint* setupBuffers(GLuint progId) {
 	GLuint vertsLen = numVerts * 3 * sizeof(GLfloat);
 	GLuint colorsLen = numVerts * 4 * sizeof(GLfloat);
 
-
-	for(int i = 0; i < 2; i++) {
-		glBindBuffer(GL_ARRAY_BUFFER, vbos[i]);
+	glBindBuffer(GL_ARRAY_BUFFER, vbo);
 	glBufferData(GL_ARRAY_BUFFER, vertsLen + colorsLen, NULL, GL_STATIC_DRAW);
 
-		glBufferSubData(GL_ARRAY_BUFFER, 0, vertsLen, vertices[i]);
+	glBufferSubData(GL_ARRAY_BUFFER, 0, vertsLen, vertices);
 	glBufferSubData(GL_ARRAY_BUFFER, vertsLen, colorsLen, colors);
 	
-		glBindVertexArray(vaos[i]);
+	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 vaos;
+	return vao;
 }
 
-void init() {
-	GLuint progId = compileShaders();
-	vaos = setupBuffers(progId);
-	
+void validateProgram(GLuint progId) {
 	glValidateProgram(progId);
 	
 	GLint success;
@@ -143,6 +126,35 @@ void init() {
 	}
 }
 
+void init() {
+	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
+		}
+	};
+
+	vaos = new GLuint[2];
+	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);
+}
+
 int main(int argc, char** argv) {
 	glutInit(&argc, argv);
 	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_3_2_CORE_PROFILE);
diff --git a/yellow.glsl b/yellow.glsl
new file mode 100644
index 0000000..d1de908
--- /dev/null
+++ b/yellow.glsl
@@ -0,0 +1,5 @@
+#version 330
+out vec4 FragColor;
+void main() {
+	FragColor = vec4(1.0, 1.0, 0.0, 1.0);
+}
-- 
2.30.2