oglplus/018_stained_glass_cube.cpp

Shows how to draw a semi-transparent textured stained glass cube

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 <oglplus/images/load.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
    Lazy<Uniform<Mat4f>> projection_matrix, camera_matrix, model_matrix;

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

    // VBOs for the cube's vertex attributes
    Buffer verts, normals, texcoords;

    // The stained glass texture
    Texture tex;
public:
    CubeExample(void)
     : cube_instr(make_cube.Instructions())
     , cube_indices(make_cube.Indices())
     , projection_matrix(prog, "ProjectionMatrix")
     , camera_matrix(prog, "CameraMatrix")
     , model_matrix(prog, "ModelMatrix")
    {
        // Set the vertex shader source
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix, ModelMatrix;"
            "in vec4 Position;"
            "in vec3 Normal;"
            "in vec2 TexCoord;"
            "out vec3 vertNormal;"
            "out vec3 vertLight;"
            "out vec2 vertTexCoord;"
            "uniform vec3 LightPos;"
            "void main(void)"
            "{"
            "   gl_Position = ModelMatrix * Position;"
            "   vertNormal = mat3(ModelMatrix)*Normal;"
            "   vertLight = LightPos - gl_Position.xyz;"
            "   vertTexCoord = TexCoord;"
            "   gl_Position = ProjectionMatrix * CameraMatrix * gl_Position;"
            "}"
        );
        // compile it
        vs.Compile();

        // set the fragment shader source
        fs.Source(
            "#version 330\n"
            "uniform sampler2D TexUnit;"
            "in vec3 vertNormal;"
            "in vec3 vertLight;"
            "in vec2 vertTexCoord;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   float l = length(vertLight);"
            "   float d = l != 0.0 ? dot(vertNormal, normalize(vertLight))/l : 0.0;"
            "   float e = (d < 0? -0.7*d: d) * 3.0;"
            "   float i = 0.1 + e;"
            "   vec4 t  = texture(TexUnit, vertTexCoord);"
            "   fragColor = vec4(t.rgb*i, t.a);"
            "}"
        );
        // 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();

        verts.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.Positions(data);
            Buffer::Data(Buffer::Target::Array, data);
            VertexArrayAttrib attr(prog, "Position");
            attr.Setup<GLfloat>(n_per_vertex);
            attr.Enable();
        }

        normals.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.Normals(data);
            Buffer::Data(Buffer::Target::Array, data);
            VertexArrayAttrib attr(prog, "Normal");
            attr.Setup<GLfloat>(n_per_vertex);
            attr.Enable();
        }

        texcoords.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.TexCoordinates(data);
            Buffer::Data(Buffer::Target::Array, data);
            VertexArrayAttrib attr(prog, "TexCoord");
            attr.Setup<GLfloat>(n_per_vertex);
            attr.Enable();
        }

        // setup the texture
        tex << Texture::Target::_2D
            << images::LoadTexture("flower_glass")
            << TextureMipmap()
            << TextureMinFilter::LinearMipmapLinear
            << TextureMagFilter::Linear
            << TextureWrap::Repeat;

        //
        UniformSampler(prog, "TexUnit").Set(0);
        Uniform<Vec3f>(prog, "LightPos").Set(Vec3f(1.0f, 2.0f, 3.0f));
        //
        gl.ClearColor(0.1f, 0.1f, 0.1f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.Enable(Capability::DepthTest);
        gl.Enable(Capability::Blend);
        gl.BlendFunc(
            BlendFn::SrcAlpha,
            BlendFn::OneMinusSrcAlpha
        );

        gl.Enable(Capability::CullFace);
        gl.FrontFace(make_cube.FaceWinding());
    }

    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(),
                6.0 - SineWave(time / 6.0) * 3.0,
                FullCircles(time * 0.7),
                Degrees(SineWave(time / 30.0) * 90)
            )
        );

        // set the model matrix
        model_matrix.Set(
            ModelMatrixf::RotationX(FullCircles(time * 0.1))
        );

        cube.Bind();
        gl.CullFace(Face::Front);
        cube_instr.Draw(cube_indices);
        gl.CullFace(Face::Back);
        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