oglplus/017_clipped_torus.cpp

Shows how to do custom clipping

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/torus.hpp>

#include <cmath>

#include "example.hpp"

namespace oglplus {

class TorusExample : public Example
{
private:
    // helper object building torus vertex attributes
    shapes::Torus make_torus;
    // helper object encapsulating torus drawing instructions
    shapes::DrawingInstructions torus_instr;
    // indices pointing to torus primitive elements
    shapes::Torus::IndexArray torus_indices;

    // wrapper around the current OpenGL context
    Context gl;

    // Program
    Program prog;
    static Program make_prog(void)
    {
        VertexShader vs;
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, ModelMatrix, CameraMatrix;"
            "uniform vec4 ClipPlane;"
            "in vec4 Position;"
            "in vec2 TexCoord;"
            "out vec2 vertTexCoord;"
            "void main(void)"
            "{"
            "   vertTexCoord = TexCoord;"
            "   gl_Position = "
            "       ModelMatrix *"
            "       Position;"
            "   gl_ClipDistance[0] = dot(ClipPlane, gl_Position);"
            "   gl_Position = "
            "       ProjectionMatrix *"
            "       CameraMatrix *"
            "       gl_Position;"
            "}"
        );
        vs.Compile();

        FragmentShader fs;
        fs.Source(
            "#version 330\n"
            "in vec2 vertTexCoord;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   float i = ("
            "       int(vertTexCoord.x*36) % 2+"
            "       int(vertTexCoord.y*24) % 2"
            "   ) % 2;"
            "   if(gl_FrontFacing)"
            "       fragColor = vec4(1-i/2, 1-i/2, 1-i/2, 1.0);"
            "   else fragColor = vec4(0+i/2, 0+i/2, 0+i/2, 1.0);"
            "}"
        );
        fs.Compile();

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

        return prog;
    }

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

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

    // VBOs for the torus's vertices and tex-coordinates
    Buffer verts;
    Buffer texcoords;
public:
    TorusExample(void)
     : make_torus(1.0, 0.5, 36, 24)
     , torus_instr(make_torus.Instructions())
     , torus_indices(make_torus.Indices())
     , prog(make_prog())
     , projection_matrix(prog, "ProjectionMatrix")
     , camera_matrix(prog, "CameraMatrix")
     , model_matrix(prog, "ModelMatrix")
    {
        Uniform<Vec4f>(prog, "ClipPlane").Set(0.0, 0.0, 1.0, 0.0);

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

        // bind the VBO for the torus vertices
        verts.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_torus.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 torus UV-coordinates
        texcoords.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_torus.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);
            attr.Enable();
        }
        //
        gl.ClearColor(0.8f, 0.8f, 0.7f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.FrontFace(make_torus.FaceWinding());
        gl.Enable(Capability::DepthTest);
        gl.Enable(Functionality::ClipDistance, 0);
    }

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

    void Render(double time)
    {
        gl.Clear().ColorBuffer().DepthBuffer();
        //
        // set the matrix for camera orbiting the origin
        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                4.5,
                FullCircles(time / 10.0),
                Degrees(45.0 + SineWave(time / 7.0)*30.0)
            )
        );
        model_matrix.Set(ModelMatrixf::RotationX(FullCircles(time / 12.0)));

        torus_instr.Draw(torus_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 TorusExample);
}

} // namespace oglplus