oglplus/001_triangle_glsl120.cpp

Shows the basic usage of OGLplus by drawing a blue triangle (using GLSL 120).

Copyright 2008-2013 Matus Chochlik. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#include <oglplus/gl.hpp>
#include <oglplus/all.hpp>

#include "example.hpp"

namespace oglplus {

class TriangleExample : public Example
{
private:
    // wrapper around the current OpenGL context
    Context gl;

    // Vertex shader
    VertexShader vs;

    // Fragment shader
    FragmentShader fs;

    // Program
    Program prog;

    // A vertex array object for the rendered triangle
    VertexArray triangle;
    // VBO for the triangle's vertices
    Buffer verts;
public:
    TriangleExample(void)
    {
        // Set the vertex shader source and compile it
        vs.Source(StrCRef(" \
            #version 120\n \
            attribute vec3 Position; \
            void main(void) \
            { \
                gl_Position = vec4(Position, 1.0); \
            } \
        ")).Compile();

        // set the fragment shader source and compile it
        fs.Source(StrCRef(" \
            #version 120\n \
            void main(void) \
            { \
                gl_FragColor = vec4(0.0, 0.0, 1.0, 1.0); \
            } \
        ")).Compile();

        // attach the shaders to the program
        prog.AttachShader(vs).AttachShader(fs);
        // link and use it
        prog.Link().Use();

        // bind the VAO for the triangle
        triangle.Bind();

        GLfloat triangle_verts[9] = {
            0.0f, 0.0f, 0.0f,
            1.0f, 0.0f, 0.0f,
            0.0f,-1.0f, 0.0f
        };
        // bind the VBO for the triangle vertices
        verts.Bind(Buffer::Target::Array);
        // upload the data
        // since triangle_vertices is a static array
        // it is not necessary to specify its element count
        Buffer::Data(Buffer::Target::Array, triangle_verts);
        // setup the vertex attribs array for the vertices
        (prog|"Position").Setup<Vec3f>().Enable();

        gl.ClearColor(0.5f, 0.5f, 0.5f, 0.0f);
        gl.Disable(Capability::DepthTest);
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
    }

    void Render(double)
    {
        gl.Clear().ColorBuffer();

        gl.DrawArrays(PrimitiveType::Triangles, 0, 3);
    }
};

void setupExample(ExampleParams& /*params*/){ }

std::unique_ptr<ExampleThread> makeExampleThread(
    Example& /*example*/,
    unsigned /*thread_id*/,
    const ExampleParams& /*params*/
){ return std::unique_ptr<ExampleThread>(); }

std::unique_ptr<Example> makeExample(const ExampleParams& /*params*/)
{
    return std::unique_ptr<Example>(new TriangleExample);
}

} // namespace oglplus