oglplus/023_reflected_cube.cpp

Shows how to draw a cube reflected in a horizontal plane

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/cage.hpp>

#include <cmath>

#include "example.hpp"

namespace oglplus {

class ReflectionExample : public Example
{
private:
    // the cube vertex attribute builder
    shapes::Cage make_cube;
    // here will be stored the indices used by the drawing instructions
    shapes::Cage::IndexArray cube_indices;
    // the instructions for drawing the cube
    shapes::DrawingInstructions cube_instr;

    // wrapper around the current OpenGL context
    Context gl;

    // Programs
    Program prog;
    static Program make_prog(void)
    {
        VertexShader vs;
        vs.Source(
            "#version 330\n"
            "in vec4 Position;"
            "in vec3 Normal;"
            "out vec3 vertColor;"
            "out vec3 vertNormal;"
            "out vec3 vertLight;"
            "uniform mat4 ProjectionMatrix, CameraMatrix, ModelMatrix;"
            "uniform vec3 LightPos;"
            "void main(void)"
            "{"
            "   gl_Position = ModelMatrix * Position;"
            "   vertColor = abs(normalize(Normal+vec3(1, 1, 1)));"
            "   vertNormal = mat3(ModelMatrix)*Normal;"
            "   vertLight = LightPos - gl_Position.xyz;"
            "   gl_Position = ProjectionMatrix * CameraMatrix * gl_Position;"
            "}"
        );
        vs.Compile();

        FragmentShader fs;
        fs.Source(
            "#version 330\n"
            "in vec3 vertColor;"
            "in vec3 vertNormal;"
            "in vec3 vertLight;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   float l = dot(vertLight, vertLight);"
            "   float d = l > 0.0 ? dot(vertNormal, normalize(vertLight)) / l : 0.0;"
            "   float i = 0.2 + max(d*3.2, 0.0);"
            "   fragColor = vec4(vertColor*i, 1.0);"
            "}"
        );
        fs.Compile();

        Program prog;
        prog.AttachShader(vs);
        prog.AttachShader(fs);
        prog.Link();

        return prog;
    }

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

    // A vertex array object for the cube
    VertexArray cube;
    // A vertex array object for the reflective plane
    VertexArray plane;

    // VBOs for the cube's vertices and normals
    Buffer cube_verts, cube_normals;
    // VBOs for the plane's vertices and normals
    Buffer plane_verts, plane_normals;
public:
    ReflectionExample(void)
     : make_cube(0.5,0.5,0.5, 0.1,0.1,0.1, 3,3,3)
     , cube_indices(make_cube.Indices())
     , cube_instr(make_cube.Instructions())
     , prog(make_prog())
     , projection_matrix(prog, "ProjectionMatrix")
     , camera_matrix(prog, "CameraMatrix")
     , model_matrix(prog, "ModelMatrix")
    {
        gl.Use(prog);

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

        // bind the VBO for the cube vertices
        gl.Bind(Buffer::Target::Array, cube_verts);
        {
            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);
            attr.Enable();
        }

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

        // bind the VAO for the plane
        gl.Bind(plane);

        // bind the VBO for the plane vertices
        gl.Bind(Buffer::Target::Array, plane_verts);
        {
            GLfloat data[4*3] = {
                -2.0f, 0.0f,  2.0f,
                -2.0f, 0.0f, -2.0f,
                 2.0f, 0.0f,  2.0f,
                 2.0f, 0.0f, -2.0f
            };
            // upload the data
            Buffer::Data(Buffer::Target::Array, 4*3, data);
            // setup the vertex attribs array for the vertices
            prog.Use();
            VertexArrayAttrib attr(prog, "Position");
            attr.Setup<Vec3f>();
            attr.Enable();
        }

        // bind the VBO for the cube normals
        gl.Bind(Buffer::Target::Array, plane_normals);
        {
            GLfloat data[4*3] = {
                -0.1f, 1.0f,  0.1f,
                -0.1f, 1.0f, -0.1f,
                 0.1f, 1.0f,  0.1f,
                 0.1f, 1.0f, -0.1f
            };
            // upload the data
            Buffer::Data(Buffer::Target::Array, 4*3, data);
            // setup the vertex attribs array for the normals
            prog.Use();
            VertexArrayAttrib attr(prog, "Normal");
            attr.Setup<Vec3f>();
            attr.Enable();
        }
        gl.Bind(NoVertexArray());

        Uniform<Vec3f>(prog, "LightPos").Set(1.5, 2.0, 2.5);
        //
        gl.ClearColor(0.2f, 0.2f, 0.2f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.ClearStencil(0);
    }

    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().StencilBuffer();
        // make the camera matrix orbiting around the origin
        // at radius of 3.5 with elevation between 15 and 90 degrees
        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                5.0,
                Degrees(time * 11),
                Degrees(15 + (-SineWave(0.25+time/12.5)+1.0)*0.5*75)
            )
        );
        ModelMatrixf identity;
        // make the model transformation matrix
        ModelMatrixf model =
            ModelMatrixf::Translation(0.0f, 1.5f, 0.0) *
            ModelMatrixf::RotationZ(Degrees(time * 43))*
            ModelMatrixf::RotationY(Degrees(time * 63))*
            ModelMatrixf::RotationX(Degrees(time * 79));
        // make the reflection matrix
        auto reflection = ModelMatrixf::Reflection(false, true, false);
        //
        gl.Disable(Capability::Blend);
        gl.Disable(Capability::DepthTest);
        gl.Enable(Capability::StencilTest);
        gl.ColorMask(false, false, false, false);
        gl.StencilFunc(CompareFunction::Always, 1, 1);
        gl.StencilOp(StencilOp::Keep, StencilOp::Keep, StencilOp::Replace);

        gl.Bind(plane);
        model_matrix.Set(identity);
        gl.DrawArrays(PrimitiveType::TriangleStrip, 0, 4);

        gl.ColorMask(true, true, true, true);
        gl.Enable(Capability::DepthTest);
        gl.StencilFunc(CompareFunction::Equal, 1, 1);
        gl.StencilOp(StencilOp::Keep, StencilOp::Keep, StencilOp::Keep);

        // draw the cube using the reflection program
        model_matrix.Set(reflection * model);
        gl.Bind(cube);
        cube_instr.Draw(cube_indices);

        gl.Disable(Capability::StencilTest);

        // draw the cube using the normal object program
        model_matrix.Set(model);
        cube_instr.Draw(cube_indices);

        // blend-in the plane
        gl.Enable(Capability::Blend);
        gl.BlendEquation(BlendEquation::Max);
        gl.Bind(plane);
        model_matrix.Set(identity);
        gl.DrawArrays(PrimitiveType::TriangleStrip, 0, 4);
    }

    bool Continue(double time)
    {
        return time < 60.0;
    }
};

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 ReflectionExample);
}

} // namespace oglplus