oglplus/020_texture_projection.cpp

Shows how to project a texture 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 <oglplus/images/load.hpp>
#include <oglplus/dsa/ext/texture.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 in prog
    Lazy<Uniform<Vec3f>> light_pos;
    Lazy<Uniform<Mat4f>>
        projection_matrix,
        tex_projection_matrix,
        model_matrix;

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

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

    // The stained glass texture
    Texture tex;
public:
    CubeExample(void)
     : cube_instr(make_cube.Instructions())
     , cube_indices(make_cube.Indices())
     , light_pos(prog, "LightPos")
     , projection_matrix(prog, "ProjectionMatrix")
     , tex_projection_matrix(prog, "TexProjectionMatrix")
     , model_matrix(prog, "ModelMatrix")
    {
        // Set the vertex shader source
        vs.Source(
            "#version 330\n"
            "uniform mat4 ProjectionMatrix, CameraMatrix, ModelMatrix;"
            "uniform mat4 TexProjectionMatrix;"
            "in vec4 Position;"
            "in vec3 Normal;"
            "out vec3 vertNormal;"
            "out vec3 vertLight;"
            "out vec4 vertTexCoord;"
            "uniform vec3 LightPos;"
            "void main(void)"
            "{"
            "   vertNormal = ("
            "       ModelMatrix *"
            "       vec4(-Normal, 0.0)"
            "   ).xyz;"
            "   vertLight = ("
            "       vec4(LightPos, 0.0)-"
            "       ModelMatrix * Position"
            "   ).xyz;"
            "   vertTexCoord = "
            "       TexProjectionMatrix *"
            "       ModelMatrix *"
            "       Position;"
            "   gl_Position = "
            "       ProjectionMatrix *"
            "       CameraMatrix *"
            "       ModelMatrix *"
            "       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 vec4 vertTexCoord;"
            "out vec4 fragColor;"
            "void main(void)"
            "{"
            "   float l = length(vertLight);"
            "   float d = l != 0.0 ? dot("
            "       vertNormal, "
            "       normalize(vertLight)"
            "   ) / l : 0.0;"
            "   float i = 0.1 + 4.2*max(d, 0.0);"
            "   vec2 coord = vertTexCoord.st/vertTexCoord.q;"
            "   vec4 t  = texture(TexUnit, coord*0.5 + 0.5);"
            "   fragColor = vec4(t.rgb*i*sqrt(1.0-t.a), 1.0);"
            "}"
        );
        // 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();
        }

        // setup the texture
        gl.DirectEXT(Texture::Target::_2D, tex)
            .Image2D(images::LoadTexture("flower_glass"))
            .GenerateMipmap()
            .BorderColor(Vec4f(1.0f, 1.0f, 1.0f, 0.0f))
            .MinFilter(TextureMinFilter::LinearMipmapLinear)
            .MagFilter(TextureMagFilter::Linear)
            .WrapS(TextureWrap::ClampToBorder)
            .WrapT(TextureWrap::ClampToBorder)
            .Bind();

        UniformSampler(prog, "TexUnit").Set(0);
        Uniform<Mat4f>(prog, "CameraMatrix").Set(
            CamMatrixf::LookingAt(Vec3f(0.0f, 1.0f, 2.0f), Vec3f())
        );

        gl.ClearColor(0.1f, 0.1f, 0.1f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.Enable(Capability::DepthTest);
        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();
        //
        Vec3f lightPos(-1.0f, 2.0f, 2.0f);
        lightPos *= (1.0f - SineWave(time/5.0f)*0.4f);
        light_pos.Set(lightPos);

        tex_projection_matrix.Set(
            CamMatrixf::PerspectiveX(Degrees(15), 1.0, 1, 20) *
            CamMatrixf::LookingAt(lightPos, Vec3f())
        );

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

        cube.Bind();
        gl.CullFace(Face::Front);
        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