oglplus/019_bpatch_tess.cpp

Shows tesellation of a cubic bezier patch

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 "example.hpp"

namespace oglplus {

class TessellationExample : public Example
{
private:
    Context gl;

    Program prog;

    Buffer positions;

    VertexArray vao;

    Lazy<Uniform<Mat4f>> projection_matrix, camera_matrix;
public:
    TessellationExample(void)
     : prog()
     , projection_matrix(prog, "ProjectionMatrix")
     , camera_matrix(prog, "CameraMatrix")
    {
        VertexShader vert(ObjectDesc("Vertex"));
        vert.Source(
            "#version 330\n"
            "uniform mat4 CameraMatrix;"

            "in vec4 Position;"
            "out vec4 vertPosition;"

            "void main(void)"
            "{"
            "   vertPosition = CameraMatrix * Position;"
            "}"
        );
        vert.Compile();
        prog << vert;

        TessControlShader teco(ObjectDesc("TessControl"));
        teco.Source(
            "#version 330\n"
            "#extension ARB_tessellation_shader: enable\n"
            "layout(vertices = 16) out;"

            "in vec4 vertPosition[];"
            "patch out vec3 tecoPosition[16];"

            "void main(void)"
            "{"
            "   if(gl_InvocationID == 0)"
            "   {"
            "       int tl = 1-int(100.0 / vertPosition[gl_InvocationID].z);"
            "       gl_TessLevelInner[0] = tl;"
            "       gl_TessLevelInner[1] = tl;"
            "       gl_TessLevelOuter[0] = tl;"
            "       gl_TessLevelOuter[1] = tl;"
            "       gl_TessLevelOuter[2] = tl;"
            "       gl_TessLevelOuter[3] = tl;"
            "   }"
            "   tecoPosition[gl_InvocationID] = "
            "       vertPosition[gl_InvocationID].xyz;"
            "}"
        );
        teco.Compile();
        prog << teco;

        TessEvaluationShader teev(ObjectDesc("TessEvaluation"));
        teev.Source(
            "#version 330\n"
            "#extension ARB_tessellation_shader: enable\n"
            "layout(quads, equal_spacing, ccw) in;"
            "uniform mat4 ProjectionMatrix;"
            "patch in vec3 tecoPosition[16];"

            "const mat4 B = mat4("
            "   -1, 3,-3, 1,"
            "    3,-6, 3, 0,"
            "   -3, 3, 0, 0,"
            "    1, 0, 0, 0 "
            ");"

            "mat4 Px, Py, Pz;"

            "void main(void)"
            "{"
            "   float u = gl_TessCoord.x, v = gl_TessCoord.y;"

            "   for(int j=0; j!=4; ++j)"
            "   for(int i=0; i!=4; ++i)"
            "   {"
            "       int k = j*4+i;"
            "       Px[j][i] = tecoPosition[k].x;"
            "       Py[j][i] = tecoPosition[k].y;"
            "       Pz[j][i] = tecoPosition[k].z;"
            "   }"

            "   mat4 Cx = B * Px * B;"
            "   mat4 Cy = B * Py * B;"
            "   mat4 Cz = B * Pz * B;"

            "   vec4 up = vec4(u*u*u, u*u, u, 1);"
            "   vec4 vp = vec4(v*v*v, v*v, v, 1);"

            "   vec4 tempPosition = vec4(dot(Cx * vp, up), dot(Cy * vp, up), dot(Cz * vp, up), 1.0);"

            "   gl_Position = ProjectionMatrix * tempPosition;"
            "}"
        );
        teev.Compile();
        prog << teev;

        FragmentShader frag(ObjectDesc("Fragment"));
        frag.Source(
            "#version 330\n"
            "out vec3 fragColor;"
            "void main(void)"
            "{"
            "   fragColor = vec3(0.1, 0.1, 0.1);"
            "}"
        );
        frag.Compile();
        prog << frag;

        prog.Link();
        prog.Use();

        vao.Bind();

        GLfloat patch_cp_pos[16*3] = {
            -2.0f,  0.0f, -2.0f,
            -1.0f,  0.0f, -3.0f,
             1.0f,  0.0f, -5.0f,
             2.0f,  0.0f, -2.0f,
            -1.0f,  0.0f, -1.0f,
             0.0f,  4.0f, -1.0f,
             1.0f,  4.0f, -1.0f,
             3.0f,  0.0f, -1.0f,
            -1.0f,  0.0f,  1.0f,
            -1.0f,  4.0f,  1.0f,
             0.0f,  4.0f,  1.0f,
             1.0f,  0.0f,  1.0f,
            -2.0f,  0.0f,  2.0f,
            -1.0f,  0.0f,  5.0f,
             1.0f,  0.0f,  3.0f,
             2.0f,  0.0f,  2.0f
        };
        positions.Bind(Buffer::Target::Array);
        Buffer::Data(Buffer::Target::Array, 16*3, patch_cp_pos);
        VertexArrayAttrib position_attr(prog, "Position");
        position_attr.Setup<Vec3f>();
        position_attr.Enable();

        gl.ClearColor(0.9f, 0.9f, 0.9f, 0.0f);
        gl.ClearDepth(1.0f);
        gl.PolygonMode(PolygonMode::Line);
        gl.PatchParameter(PatchParameter::PatchVertices, 16);
    }

    void Reshape(GLuint width, GLuint height)
    {
        gl.Viewport(width, height);
        projection_matrix.Set(
            CamMatrixf::PerspectiveX(
                Degrees(70),
                double(width)/height,
                1, 100
            )
        );
    }

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

        camera_matrix.Set(
            CamMatrixf::Orbiting(
                Vec3f(),
                30.0 - SineWave(time / 17.0)*25.0,
                Degrees(time * 47),
                Degrees(SineWave(time / 31.0) * 90)
            )
        );

        gl.DrawArrays(PrimitiveType::Patches, 0, 16);
    }
};

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 TessellationExample);
}

} // namespace oglplus