oglplus/003_triangle.cpp

Shows the basic usage of OGLplus by drawing a simple transformed triangle.

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;

    // Array of VBOs [0] -> vertex coords, [1] -> vertex colors
    Array<Buffer> buffs;
public:
    TriangleExample(void)
     : buffs(2)
    {
        // Set the vertex shader source
        vs.Source(" \
            #version 330\n \
            in vec3 Position; \
            in vec3 Color; \
            uniform mat4 Matrix; \
            out vec4 vertColor; \
            void main(void) \
            { \
                gl_Position = Matrix * vec4(Position, 1.0); \
                vertColor = vec4(Color, 1.0); \
            } \
        ");
        // compile it
        vs.Compile();

        // set the fragment shader source
        fs.Source(" \
            #version 330\n \
            in vec4 vertColor; \
            out vec4 fragColor; \
            void main(void) \
            { \
                fragColor = vertColor; \
            } \
        ");
        // compile it
        fs.Compile();

        // attach the shaders to the program
        prog.AttachShader(vs);
        prog.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
        buffs[0].Bind(Buffer::Target::Array);
        // upload the data
        Buffer::Data(Buffer::Target::Array, triangle_verts);
        // setup the vertex attribs array for the vertices
        VertexArrayAttrib vert_attr(prog, "Position");
        vert_attr.Setup<Vec3f>();
        vert_attr.Enable();
        //

        GLfloat triangle_colors[9] = {
            1.0f, 0.0f, 0.0f,
            0.0f, 1.0f, 0.0f,
            0.0f, 0.0f, 1.0f
        };
        // bind the VBO for the triangle colors
        buffs[1].Bind(Buffer::Target::Array);
        // upload the data
        Buffer::Data(Buffer::Target::Array, triangle_colors);
        // setup the vertex attribs array
        VertexArrayAttrib color_attr(prog, "Color");
        color_attr.Setup<Vec3f>();
        color_attr.Enable();

        // set the transformation matrix
        Uniform<Mat4f> u1(prog, "Matrix");
        u1.Set(Mat4f(
             Vec4f(2.0f,  0.0f,  0.0f, -1.0f),
             Vec4f(0.0f,  2.0f,  0.0f, -1.0f),
             Vec4f(0.0f,  0.0f,  2.0f,  0.0f),
             Vec4f(0.0f,  0.0f,  0.0f,  1.0f)
        ));

        gl.ClearColor(1.0f, 1.0f, 1.0f, 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