oglplus/012_checker_sphere.cpp

Shows how to draw a checkered sphere using the Sphere 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/sphere.hpp>

#include <cmath>

#include "example.hpp"

namespace oglplus {

class SphereExample : public Example
{
private:
    // helper object building sphere vertex attributes
    shapes::Sphere make_sphere;
    // helper object encapsulating sphere drawing instructions
    shapes::DrawingInstructions sphere_instr;
    // indices pointing to sphere primitive elements
    shapes::Sphere::IndexArray sphere_indices;

    // wrapper around the current OpenGL context
    Context gl;

    // Program
    Program prog;

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

    // VBOs for the sphere's vertices and tex-coordinates
    Buffer verts;
    Buffer texcoords;

    // Uniform variables
    Lazy<Uniform<Mat4f>> projection_matrix;
    Lazy<Uniform<Mat4f>> camera_matrix;
public:
    SphereExample(void)
     : sphere_instr(make_sphere.Instructions())
     , sphere_indices(make_sphere.Indices())
     , projection_matrix(prog, "ProjectionMatrix")
     , camera_matrix(prog, "CameraMatrix")
    {
        // Vertex shader
        VertexShader vs;
        // Set the vertex shader source and compile it
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix;"
            "layout(location = 0) in vec4 Position;"
            "layout(location = 1) in vec2 TexCoord;"
            "out vec2 vertTexCoord;"
            "void main(void)"
            "{"
            "   vertTexCoord = TexCoord;"
            "   gl_Position = "
            "       ProjectionMatrix *"
            "       CameraMatrix *"
            "       Position;"
            "}"
        ).Compile();

        // Fragment shader
        FragmentShader fs;
        // 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*18) % 2+"
            "       int(vertTexCoord.y*14) % 2"
            "   ) % 2;"
            "   fragColor = vec4(1-i/2, 1-i/2, 1-i/2, 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 sphere
        sphere.Bind();

        // bind the VBO for the sphere vertices
        verts.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_sphere.Positions(data);
            // upload the data
            Buffer::Data(Buffer::Target::Array, data);
            // setup the vertex attribs array for the vertices
            // (prog|0) is equivalent to VertexArrayAttrib(prog, VertexAtribSlot(0))
            (prog|0).Setup<GLfloat>(n_per_vertex).Enable();
        }

        // bind the VBO for the sphere UV-coordinates
        texcoords.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_sphere.TexCoordinates(data);
            // upload the data
            Buffer::Data(Buffer::Target::Array, data);
            // setup the vertex attribs array for the vertices
            // (prog|1) is equivalent to VertexArrayAttrib(prog, VertexAtribSlot(1))
            (prog|1).Setup<GLfloat>(n_per_vertex).Enable();
        }
        //
        gl.ClearColor(0.8f, 0.8f, 0.7f, 0.0f);
        gl.ClearDepth(1.0f);
        Capability::DepthTest << true;
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
        prog.Use();
        projection_matrix.Set(
            CamMatrixf::PerspectiveX(
                Degrees(60),
                double(width)/height,
                1, 20
            )
        );
    }

    void Render(double time)
    {
        gl.Clear().ColorBuffer().DepthBuffer();
        //
        // set the matrix for camera orbiting the origin
        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                3.5,
                Degrees(time * 135),
                Degrees(SineWave(time / 20.0) * 90)
            )
        );

        sphere_instr.Draw(sphere_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 SphereExample);
}

} // namespace oglplus