oglplus/010_rgb_cube.cpp

Shows how to draw a RGB colored cube

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 CubeExample : 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 cube
    VertexArray cube;

    // VBOs for the cube's vertices and normals
    Buffer verts;
    Buffer normals;
public:
    CubeExample(void)
    {
        // Set the vertex shader source
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix;"
            "in vec4 Position;"
            "in vec3 Normal;"
            "out vec3 vertNormal;"
            "void main(void)"
            "{"
            "   vertNormal = Normal;"
            "   gl_Position = ProjectionMatrix *"
            "       CameraMatrix *"
            "       Position;"
            "}"
        );
        // compile it
        vs.Compile();

        // set the fragment shader source
        // (uses the absolute value of normal as color)
        fs.Source(
            "#version 330\n"
            "in vec3 vertNormal;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   fragColor = vec4(abs(vertNormal), 1.0);"
            "}"
        );
        // compile it
        fs.Compile();

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

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

        const GLfloat c[8][3] = {
            {-0.5f, -0.5f, +0.5f},
            {-0.5f, -0.5f, -0.5f},
            {-0.5f, +0.5f, -0.5f},
            {-0.5f, +0.5f, +0.5f},
            {+0.5f, -0.5f, +0.5f},
            {+0.5f, -0.5f, -0.5f},
            {+0.5f, +0.5f, -0.5f},
            {+0.5f, +0.5f, +0.5f}
        };
        const GLuint vertex_count = 6 * 2 * 3;
        const GLfloat cube_vertices[vertex_count * 3] = {
            c[0][0], c[0][1], c[0][2],
            c[2][0], c[2][1], c[2][2],
            c[1][0], c[1][1], c[1][2],
            c[0][0], c[0][1], c[0][2],
            c[3][0], c[3][1], c[3][2],
            c[2][0], c[2][1], c[2][2],

            c[0][0], c[0][1], c[0][2],
            c[1][0], c[1][1], c[1][2],
            c[4][0], c[4][1], c[4][2],
            c[1][0], c[1][1], c[1][2],
            c[5][0], c[5][1], c[5][2],
            c[4][0], c[4][1], c[4][2],

            c[1][0], c[1][1], c[1][2],
            c[2][0], c[2][1], c[2][2],
            c[5][0], c[5][1], c[5][2],
            c[2][0], c[2][1], c[2][2],
            c[6][0], c[6][1], c[6][2],
            c[5][0], c[5][1], c[5][2],

            c[4][0], c[4][1], c[4][2],
            c[5][0], c[5][1], c[5][2],
            c[6][0], c[6][1], c[6][2],
            c[4][0], c[4][1], c[4][2],
            c[6][0], c[6][1], c[6][2],
            c[7][0], c[7][1], c[7][2],

            c[2][0], c[2][1], c[2][2],
            c[3][0], c[3][1], c[3][2],
            c[7][0], c[7][1], c[7][2],
            c[2][0], c[2][1], c[2][2],
            c[7][0], c[7][1], c[7][2],
            c[6][0], c[6][1], c[6][2],

            c[0][0], c[0][1], c[0][2],
            c[4][0], c[4][1], c[4][2],
            c[3][0], c[3][1], c[3][2],
            c[3][0], c[3][1], c[3][2],
            c[4][0], c[4][1], c[4][2],
            c[7][0], c[7][1], c[7][2]
        };
        // bind the VBO for the cube vertices
        verts.Bind(Buffer::Target::Array);
        // upload the data
        Buffer::Data(
            Buffer::Target::Array,
            vertex_count * 3,
            cube_vertices
        );
        // setup the vertex attribs array for the vertices
        VertexArrayAttrib vert_attr(prog, "Position");
        vert_attr.Setup<Vec3f>();
        vert_attr.Enable();

        const GLfloat n[6][3] = {
            {-1.0f,  0.0f,  0.0f},
            { 0.0f, -1.0f,  0.0f},
            { 0.0f,  0.0f, -1.0f},
            { 1.0f,  0.0f,  0.0f},
            { 0.0f,  1.0f,  0.0f},
            { 0.0f,  0.0f,  1.0f}
        };
        GLfloat cube_normals[vertex_count * 3];
        for(GLuint f=0;f!=6;++f)
            for(GLuint v=0;v!=6;++v)
                for(GLuint ci=0;ci!=3;++ci)
                    cube_normals[(f*6+v)*3+ci] = n[f][ci];
        // bind the VBO for the cube normals
        normals.Bind(Buffer::Target::Array);
        // upload the data
        Buffer::Data(
            Buffer::Target::Array,
            vertex_count * 3,
            cube_normals
        );
        // setup the vertex attribs array for the vertices
        VertexArrayAttrib normal_attr(prog, "Normal");
        normal_attr.Setup<Vec3f>();
        normal_attr.Enable();
        //
        // set the matrix for camera at (1,1,1) looking at origin
        Uniform<Mat4f>(prog, "CameraMatrix").Set(
            CamMatrixf::LookingAt(
                Vec3f(2.0f, 2.0f, 2.0f),
                Vec3f()
            )
        );
        //
        gl.ClearColor(1.0f, 1.0f, 1.0f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.Enable(Capability::DepthTest);
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
        prog.Use();
        Uniform<Mat4f>(prog, "ProjectionMatrix").Set(
            CamMatrixf::PerspectiveX(
                Degrees(48),
                GLfloat(width)/height,
                1, 100
            )
        );
    }

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

        gl.DrawArrays(PrimitiveType::Triangles, 0, 6 * 2 * 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 CubeExample);
}

} // namespace oglplus