oglplus/006_cartoon_sun.cpp

Shows how to render a rectangle with an animated sun drawing

Copyright 2008-2013 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 "example.hpp"

#include <cmath>

namespace oglplus {

class RectangleExample : public Example
{
private:
    // wrapper around the current OpenGL context
    Context gl;

    // Vertex shader
    VertexShader vs;

    // Fragment shader
    FragmentShader fs;

    // Program
    Program prog;

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

    // VBOs for the rectangle's vertices used also as the viewport coords
    Buffer verts;
public:
    RectangleExample(void)
    {
        // Set the vertex shader source and compile it
        vs.Source(
            "#version 330\n"
            "in vec2 Position;"
            "out vec2 vertPos;"
            "void main(void)"
            "{"
            "   gl_Position = vec4(Position, 0.0, 1.0);"
            "   vertPos = gl_Position.xy;"
            "}"
        ).Compile();

        // set the fragment shader source and compile it
        fs.Source(
            "#version 330\n"
            "uniform float Time;"
            "uniform vec2 SunPos;"
            "uniform vec3 Sun1, Sun2, Sky1, Sky2;"
            "in vec2 vertPos;"
            "out vec3 fragColor;"
            "void main(void)"
            "{"
            "   vec2 v = vertPos - SunPos;"
            "   float l = length(v);"
            "   float a = (sin(l)+atan(v.y, v.x))/3.1415;"
            "   if(l < 0.1)"
            "       fragColor = Sun1;"
            "   else if(int(18*(Time*0.1 + 1.0 + a)) % 2 == 0)"
            "       fragColor = mix(Sun1, Sun2, l);"
            "   else"
            "       fragColor = mix(Sky1, Sky2, l);"
            "}"
        ).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 rectangle
        rectangle.Bind();

        GLfloat rectangle_verts[8] = {
            -1.0f, -1.0f,
            -1.0f,  1.0f,
             1.0f, -1.0f,
             1.0f,  1.0f
        };
        // bind the VBO for the rectangle vertices
        verts.Bind(Buffer::Target::Array);
        // upload the data
        Buffer::Data(Buffer::Target::Array, rectangle_verts);
        // setup the vertex attribs array for the vertices
        (prog|"Position").Setup<Vec2f>().Enable();
        //
        // Uniforms can be typechecked
        // but note that the typechecking is a relatively
        // expensive operation
        Typechecked<Uniform<Vec3f>>(prog, "Sun1").Set(0.95f, 0.85f, 0.60f);
        Typechecked<Uniform<Vec3f>>(prog, "Sun2").Set(0.90f, 0.80f, 0.20f);
        Typechecked<Uniform<Vec3f>>(prog, "Sky1").Set(0.90f, 0.80f, 0.50f);
        Typechecked<Uniform<Vec3f>>(prog, "Sky2").Set(0.80f, 0.60f, 0.40f);
        //
        gl.Disable(Capability::DepthTest);
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
    }

    void Render(double time)
    {
        gl.Clear().ColorBuffer();

        auto angle = FullCircles(GLfloat(time * 0.05f));
        Uniform<GLfloat>(prog, "Time").Set(GLfloat(time));
        Uniform<Vec2f>(prog, "SunPos").Set(
            -Cos(angle),
            Sin(angle)
        );
        gl.DrawArrays(PrimitiveType::TriangleStrip, 0, 4);
    }

    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 RectangleExample);
}

} // namespace oglplus