oglplus/019_subsurf_scatter.cpp

Shows a very simple subsurface scattering on a 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 <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;
    Lazy<Uniform<GLint>> front_facing;

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

    // VBOs for the cube's vertices and normals
    Buffer verts, normals;

    // number of instances of the cube that we are going to draw
    int inst_count;
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")
     , front_facing(prog, "FrontFacing")
     , inst_count(32)
    {
        // Set the vertex shader source
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix, ModelMatrix;"
            "uniform vec3 LightPos;"
            "uniform int InstCount;"
            "uniform int FrontFacing;"
            "in vec4 Position;"
            "in vec3 Normal;"
            "out float vertMult;"
            "out vec3 vertColor;"
            "out vec3 vertWrapNormal;"
            "out vec3 vertNormal;"
            "out vec3 vertLight;"
            "void main(void)"
            "{"
            "   int inst = (FrontFacing != 0) ? "
            "       (InstCount - gl_InstanceID - 1):"
            "       gl_InstanceID;"
            "   vertMult = float(inst) / float(InstCount-1);"
            "   float sca = 1.0 - 0.3 * pow(vertMult, 2);"
            "   mat4 ScaleMatrix = mat4("
            "       sca, 0.0, 0.0, 0.0,"
            "       0.0, sca, 0.0, 0.0,"
            "       0.0, 0.0, sca, 0.0,"
            "       0.0, 0.0, 0.0, 1.0 "
            "   );"
            "   gl_Position = ModelMatrix * Position;"
            "   vertColor = Normal;"
            "   vec3 wrap = Position.xyz - Normal;"
            "   vertWrapNormal = "
            "       mat3(ModelMatrix)*"
            "       normalize(mix("
            "           Normal,"
            "           wrap,"
            "           mix(0.5, 1.0, vertMult)"
            "       ));"
            "   vertNormal = mat3(ModelMatrix)*Normal;"
            "   vertLight = LightPos-gl_Position.xyz;"
            "   gl_Position = "
            "       ProjectionMatrix *"
            "       CameraMatrix *"
            "       ScaleMatrix *"
            "       gl_Position;"
            "}"
        );
        // compile it
        vs.Compile();

        // set the fragment shader source
        fs.Source(
            "#version 330\n"
            "in float vertMult;"
            "in vec3 vertColor;"
            "in vec3 vertWrapNormal;"
            "in vec3 vertNormal;"
            "in vec3 vertLight;"
            "out vec4 fragColor;"
            "uniform int InstCount;"
            "void main(void)"
            "{"
            "   float l = dot(vertLight, vertLight);"
            "   float d = l > 0.0 ? dot("
            "       vertNormal, "
            "       normalize(vertLight)"
            "   ) / l : 0.0;"
            "   float s = max("
            "       dot(vertWrapNormal, vertLight)/l,"
            "       0.0"
            "   );"
            "   float intensity = clamp("
            "       0.2 + d * 3.0 + s * 5.5,"
            "       0.0,"
            "       1.0"
            "   );"
            "   fragColor = vec4("
            "       abs(vertColor) * intensity,"
            "       (2.5 + 1.5*d + 1.5*s) / InstCount"
            "   );"
            "}"
        );
        // 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();

        // bind the VBO for the cube vertices
        verts.Bind(Buffer::Target::Array);
        {
            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
        normals.Bind(Buffer::Target::Array);
        {
            std::vector<GLfloat> data;
            GLuint n_per_vertex = make_cube.Normals(data);
            // upload the data
            Buffer::Data(Buffer::Target::Array, data);
            VertexArrayAttrib attr(prog, "Normal");
            attr.Setup<GLfloat>(n_per_vertex);
            attr.Enable();
        }
        // the light position
        Uniform<Vec3f>(prog, "LightPos").Set(Vec3f(-3.0f, -2.0f, -3.0f));
        // and the instance count
        Uniform<GLint>(prog, "InstCount").Set(inst_count);
        //
        gl.ClearColor(0.5f, 0.6f, 0.5f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.Enable(Capability::DepthTest);
        gl.Enable(Capability::CullFace);
        gl.FrontFace(make_cube.FaceWinding());
        gl.Enable(Capability::Blend);
        gl.BlendFunc(BlendFn::SrcAlpha, BlendFn::OneMinusSrcAlpha);
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
        prog.Use();
        projection_matrix.Set(
            CamMatrixf::PerspectiveX(
                Degrees(70),
                double(width)/height,
                1, 20
            )
        );
    }

    void Render(double time)
    {
        gl.Clear().ColorBuffer().DepthBuffer();
        //
        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                3.0f,
                Degrees(time * 50),
                Degrees(SineWave(time / 16.0) * 80)
            )
        );
        // the model matrix
        model_matrix.Set(
            ModelMatrixf::RotationY(Degrees(time * 25))
        );
        // draw 36 instances of the cube
        // first the back faces
        gl.CullFace(Face::Front);
        front_facing.Set(0);
        cube_instr.Draw(cube_indices, inst_count);
        // then the front faces
        gl.CullFace(Face::Back);
        front_facing.Set(1);
        cube_instr.Draw(cube_indices, inst_count);
    }

    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