oglplus/013_striped_cubes.cpp

Shows how to draw rotating striped cubes using the Cube builder

Copyright 2008-2014 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 <oglplus/shapes/cube.hpp>

#include <cmath>

#include "example.hpp"

namespace oglplus {

class CubeExample : public Example
{
private:
    // helper object building cube vertex attributes
    shapes::Cube make_cube;
    // helper object encapsulating cube drawing instructions
    shapes::DrawingInstructions cube_instr;
    // indices pointing to cube primitive elements
    shapes::Cube::IndexArray cube_indices;

    // wrapper around the current OpenGL context
    Context gl;

    // Vertex shader
    VertexShader vs;

    // Fragment shader
    FragmentShader fs;

    // Program
    Program prog;

    // Uniforms
    Uniform<Mat4f> projection_matrix, camera_matrix, model_matrix;

    // A vertex array object for the rendered cube
    VertexArray cube;

    // VBOs for the cube's vertices and tex-coordinates
    Buffer verts;
    Buffer texcoords;
public:
    CubeExample(void)
     : cube_instr(make_cube.Instructions())
     , cube_indices(make_cube.Indices())
     , projection_matrix(prog)
     , camera_matrix(prog)
     , model_matrix(prog)
    {
        // Set the vertex shader source and compile it
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix, ModelMatrix;"
            "in vec4 Position;"
            "in vec2 TexCoord;"
            "out vec2 vertTexCoord;"
            "void main(void)"
            "{"
            "   vertTexCoord = TexCoord;"
            "   gl_Position = "
            "       ProjectionMatrix *"
            "       CameraMatrix *"
            "       ModelMatrix *"
            "       Position;"
            "}"
        ).Compile();

        // set the fragment shader source and compile it
        fs.Source(
            "#version 330\n"
            "in vec2 vertTexCoord;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   float i = int(("
            "       vertTexCoord.x+"
            "       vertTexCoord.y "
            "   )*8) % 2;"
            "   fragColor = mix("
            "       vec4(0, 0, 0, 1),"
            "       vec4(1, 1, 0, 1),"
            "       i"
            "   );"
            "}"
        ).Compile();

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

        // initialize the uniforms
        projection_matrix.BindTo("ProjectionMatrix");
        camera_matrix.BindTo("CameraMatrix");
        model_matrix.BindTo("ModelMatrix");

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

        // bind the VBO for the cube vertices
        verts.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.Positions(data);
            // upload the data
            Buffer::Data(Buffer::Target::Array, data);
            // setup the vertex attribs array for the vertices
            VertexArrayAttrib attr(prog, "Position");
            attr.Setup<GLfloat>(n_per_vertex).Enable();
        }

        // bind the VBO for the cube UV-coordinates
        texcoords.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.TexCoordinates(data);
            // upload the data
            Buffer::Data(Buffer::Target::Array, data);
            // setup the vertex attribs array for the vertices
            VertexArrayAttrib attr(prog, "TexCoord");
            attr.Setup<GLfloat>(n_per_vertex).Enable();
        }

        +Capability::DepthTest;
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
        prog.Use();
        projection_matrix.Set(
            CamMatrixf::PerspectiveX(
                Degrees(60),
                double(width)/height,
                1, 30
            )
        );
    }

    void Render(double time)
    {
        const GLfloat clear_color[4] = {0.8f, 0.8f, 0.7f, 0.0f};
        gl.ClearColorBuffer(0, clear_color);
        gl.ClearDepthBuffer(1.0f);
        //
        // set the matrix for camera orbiting the origin
        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                3.5,
                Degrees(time * 15),
                Degrees(SineWave(time / 6.3) * 45)
            )
        );
        model_matrix.Set(
            ModelMatrixf::Translation(-1.0, 0.0, 0.0) *
            ModelMatrixf::RotationZ(Degrees(time * 180))
        );
        cube_instr.Draw(cube_indices);
        model_matrix.Set(
            ModelMatrixf::Translation(+1.0, 0.0, 0.0) *
            ModelMatrixf::RotationY(Degrees(time * 90))
        );
        cube_instr.Draw(cube_indices);
    }

    bool Continue(double time)
    {
        return time < 30.0;
    }
};

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