Why don't these GLSL shaders work? - c++

Question

I'm trying to render a spiral as all red using the shaders to override the colours. For some reason they compile and link but do nothing.
See the following code
fragmentshader.glsl
#version 430
out vec4 outColor;
in vec4 color;
void main(){
outColor = color;
}
vertexshader.glsl
#version 430
in layout(location=0) vec2 position;
out vec4 color;
void main(){
gl_Position = vec4(position, 0.0, 1.0);
color = vec4(1.0, 0.0f, 0.0f, 1.0f);
}
Window.cpp
#include <GL\glew.h>
#include <glm\glm.hpp>
#include <glm\gtc\matrix_transform.hpp>
#include "MeGLWindow.h"
#include <iostream>
#include <fstream>
#define Pi 3.14159265358979
#define E 2.718281828F
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600
#define MAX_SPIRAL 25000
std::string readFile(const char* relPath);
void installShaders();
bool checkShaderStatus(GLuint shaderID);
bool checkProgramStatus(GLuint programID);
GLuint programID;
void MeGLWindow::initializeGL() {
glewInit();
glEnable(GL_DEPTH_TEST);
installShaders();
const int verts_num = MAX_SPIRAL * 2;
GLfloat verts[50000];
GLuint myBufferID;
float a = 0.06f;
float b = 0.06f;
float cx = 0.0;
float cy = 0.0;
int z = 0;
for (int i = 0; i < MAX_SPIRAL; i++) {
float ang = (Pi / 720) * i;
float factor = pow(E, b * ang);
float x = cx + (a * (cos(ang)) * factor);
float y = cy - (a * (sin(ang)) * factor);
verts[2 * i] = x;
verts[(2 * i) + 1] = y;
}
glGenBuffers(1, &myBufferID);
glBindBuffer(GL_ARRAY_BUFFER, myBufferID);
glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
}
void MeGLWindow::paintGL() {
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glViewport(0, 0, width(), height());
glDrawArrays(GL_POINTS, 0, 2*25000);
}
void installShaders() {
GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER);
GLuint fragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);
const char* adapter[1];
std::string file = readFile("vertexshader.glsl");
const char* vertexFile = file.c_str();
adapter[0] = vertexFile;
glShaderSource(vertexShaderID, 1, adapter, 0);
file = readFile("fragmentshader.glsl");
const char* fragmentFile = file.c_str();
adapter[0] = fragmentFile;
glShaderSource(fragmentShaderID, 1, adapter, 0);
glCompileShader(vertexShaderID);
glCompileShader(fragmentShaderID);
if (!checkShaderStatus(vertexShaderID) || !checkShaderStatus(fragmentShaderID)) {
return;
}
programID = glCreateProgram();
glAttachShader(programID, vertexShaderID);
glAttachShader(programID, fragmentShaderID);
glLinkProgram(programID);
if (!checkProgramStatus(programID)) {
return;
}
glUseProgram(programID);
}
main.cpp
#include <Qt\qapplication.h>
#include "MeGLWindow.h"
int main(int argc, char* argv[]) {
QApplication app(argc, argv);
MeGLWindow meWindow;
meWindow.show();
return app.exec();
}
The vertices in the spiral should be red according to the linked shaders! What am i doing wrong? Please help!

Answer 1

No error checking on the shader program. Or rather, you check for errors, but don't signal the application that the program creation failed in any way.
You don't provide the source for checkProgramStatus, but if you checking for GL_LINK_STATUS, you're doing so before you link the problem.
It's not clear how you're initializing OpenGL from the code provided, but you're not setting a VAO, which is required for the core profile.