I am using Mesa 10.1.3 to be able to use OpenGL 3.3 on my Linux computer. I request a core profile when I create the window since only the core profile has OpenGL 3.3. But when I tried to write a simple program to display a triangle on the screen, I got nothing. So I thought I screwed up somewhere in the code but I rechecked it and it was correct. To test this, I tried running the program in Windows and it was working as it should. So I experimented a little bit more with the code; I multiplied the vertex location in the vertex shader by 0.001 and only then I was able to see my triangle, but even then, it was not working as it should. The triangle I see was a right angle triangle whereas I intended it to be an equilateral one (in Windows I see an equilateral triangle). So my guess is vertex location is somehow different when using OpenGL Core profile, but I don't quite know how to fix this. What am I doing wrong and what should I be doing?
By the way, this is my vertex shader looks like:
#version 330
in vec3 position;
void main()
{
gl_Position = vec4(0.001*position, 1.0);
}
Fragment shader:
#version 330
out vec4 fragColor;
void main()
{
fragColor = vec4(0.0, 1.0, 1.0, 1.0);
}
Shader class:
public Shader()
{
program = glCreateProgram();
if(program == 0)
{
System.err.println("Shader creation failed: Could not find valid memory location");
System.exit(1);
}
}
public void bind()
{
glBindAttribLocation(program, 0, "position");
glUseProgram(program);
}
public void addVertexShader(String text)
{
addProgram(text, GL_VERTEX_SHADER);
}
public void addFragmentShader(String text)
{
addProgram(text, GL_FRAGMENT_SHADER);
}
public void addGeometryShader(String text)
{
addProgram(text, GL_GEOMETRY_SHADER);
}
public void compile()
{
glLinkProgram(program);
if(glGetProgrami(program, GL_LINK_STATUS) == 0)
{
System.err.println(glGetProgramInfoLog(program, 1024));
System.exit(1);
}
glValidateProgram(program);
if(glGetProgrami(program, GL_VALIDATE_STATUS) == 0)
{
System.err.println(glGetProgramInfoLog(program, 1024));
System.exit(1);
}
}
public void addProgram(String text, int type)
{
int shader = glCreateShader(type);
if(shader == 0)
{
System.err.println("Shader creation failed");
System.exit(1);
}
glShaderSource(shader, text);
glCompileShader(shader);
if(glGetShaderi(shader, GL_COMPILE_STATUS) == 0)
{
System.err.println(glGetShaderInfoLog(shader, 1024));
System.exit(1);
}
glAttachShader(program, shader);
}
And my array of vertices which I'm creating the VBO with:
Vertex[] data = new Vertex[] {
new Vertex(new Vector3f(-0.1f, -0.1f, 0)),
new Vertex(new Vector3f(0, 1, 0)),
new Vertex(new Vector3f( 1, -1, 0))};
My draw method:
public void draw()
{
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
//Vertex is a class which only holds a Vector3f for position, currently, so size is set to 3
glVertexAttribPointer(0, 3, GL_FLOAT, false, Vertex.SIZE * 4, 0);
glDrawArrays(GL_TRIANGLES, 0, size);
glDisableVertexAttribArray(0);
}
And this is the result that I'm getting: