MarbleShader
vtk-examples/Cxx/Shaders/MarbleShader
Description¶
This example shows how to add user functions to a VTK shader. The example's fragment shader uses an implementation of Ken Perlin's noise function. Perlin received a Technical Achievement Academy Award for his work procedural texture.
The file for the shader code is src/Testing/Data/Shaders/PerlinNoise.glsl.
Parameters¶
- veinfreq - controls the lowest frequency of the color veins e.g. 10
- veinlevels - how many "levels" of vein tendrils it has e.g. 2
- warpfreq - lowest frequency of the turbulent warping in the marble e.g. 10
- _ warping_ - controls how much turbulent warping there will be e.g. 0.5
- veincolor - the color of the veins e.g. white: 1 1 1
- sharpness - controls how sharp or fuzzy the veins are (higher = sharper) e.g. 8
Cite
Perlin's original Siggraph Paper: Perlin, K. 1985. "An Image Synthesizer." Computer Graphics 19(3).
Cite
This shader is inspired by Larry Gritz's veined marble shader.
Question
If you have a question about this example, please use the VTK Discourse Forum
Code¶
MarbleShader.cxx
#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOpenGLPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkShaderProgram.h>
#include <vtkSmartPointer.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkTriangleFilter.h>
#include <vtkTriangleMeshPointNormals.h>
#include <vtkVersion.h>
#include <vtksys/SystemTools.hxx>
#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>
#if VTK_VERSION_NUMBER >= 89000000000ULL
#define USE_SHADER_PROPERTIES 1
#include <vtkShaderProperty.h>
#endif
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
namespace {
// -----------------------------------------------------------------------
// Update uniform variables in the shader for each render. We do this with a
// callback for the UpdateShaderEvent
class ShaderCallback : public vtkCommand
{
public:
static ShaderCallback* New()
{
return new ShaderCallback;
}
vtkRenderer* Renderer;
float veincolor[3];
float veinfreq;
int veinlevels;
float warpfreq;
float warping;
float sharpness;
void Execute(vtkObject*, unsigned long, void* calldata) override
{
vtkShaderProgram* program = reinterpret_cast<vtkShaderProgram*>(calldata);
if (program)
{
program->SetUniform3f("veincolor", veincolor);
program->SetUniformf("veinfreq", veinfreq);
program->SetUniformi("veinlevels", veinlevels);
program->SetUniformf("warpfreq", warpfreq);
program->SetUniformf("warping", warping);
program->SetUniformf("sharpness", sharpness);
}
}
void Print(std::ostream& os)
{
os << "veincolor: " << veincolor[0] << ", " << veincolor[1] << ", "
<< veincolor[2] << std::endl;
os << "veinfreq: " << veinfreq << std::endl;
os << "veinlevels: " << veinlevels << std::endl;
os << "warpfreq: " << warpfreq << std::endl;
os << "warping: " << warping << std::endl;
os << "sharpness: " << sharpness << std::endl;
}
ShaderCallback()
{
this->Renderer = nullptr;
this->veincolor[0] = this->veincolor[1] = this->veincolor[2] = 1.0;
this->veinfreq = 10.0;
this->veinlevels = 2;
this->warpfreq = 1.0;
this->warping = .5;
this->sharpness = 8.0;
}
};
} // namespace
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName);
}
//----------------------------------------------------------------------------
int main(int argc, char* argv[])
{
if (argc < 2)
{
std::cout << "Usage: " << argv[0] << " PerlnNoise.glsl "
<< "[polydataFile] "
<< "[veincolor(1,1,1)] "
<< "[veinfreq(10)] "
<< "[veinlevels(2)] "
<< "[warpfreq(1)] "
<< "[warping(.5)] "
<< "[sharpness(8)]" << std::endl;
return EXIT_FAILURE;
}
auto polyData = ReadPolyData(2 ? argv[2] : "");
std::ifstream shaderFile(argv[1]);
std::ostringstream shaderCode;
shaderCode << shaderFile.rdbuf();
// Create a transform to rescale model
double center[3];
polyData->GetCenter(center);
double bounds[6];
polyData->GetBounds(bounds);
double maxBound =
std::max(std::max(bounds[1] - bounds[0], bounds[3] - bounds[2]),
bounds[5] - bounds[4]);
vtkNew<vtkNamedColors> colors;
vtkNew<vtkActor> actor;
vtkNew<vtkRenderer> renderer;
vtkNew<vtkOpenGLPolyDataMapper> mapper;
renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->SetSize(640, 480);
renderWindow->AddRenderer(renderer);
renderer->AddActor(actor);
vtkNew<vtkRenderWindowInteractor> interactor;
interactor->SetRenderWindow(renderWindow);
// Rescale polydata to [-1,1]
vtkNew<vtkTransform> userTransform;
userTransform->Translate(-center[0], -center[1], -center[2]);
userTransform->Scale(1.0 / maxBound, 1.0 / maxBound, 1.0 / maxBound);
vtkNew<vtkTransformPolyDataFilter> transform;
transform->SetTransform(userTransform);
transform->SetInputData(polyData);
vtkNew<vtkTriangleFilter> triangles;
triangles->SetInputConnection(transform->GetOutputPort());
vtkNew<vtkTriangleMeshPointNormals> norms;
norms->SetInputConnection(triangles->GetOutputPort());
mapper->SetInputConnection(norms->GetOutputPort());
mapper->ScalarVisibilityOff();
actor->SetMapper(mapper);
actor->GetProperty()->SetDiffuse(1.0);
actor->GetProperty()->SetDiffuseColor(
colors->GetColor3d("ivoryblack").GetData());
actor->GetProperty()->SetSpecular(.5);
actor->GetProperty()->SetSpecularPower(5);
// Modify the vertex shader to pass the position of the vertex
#if USE_SHADER_PROPERTIES
vtkShaderProperty* sp = actor->GetShaderProperty();
sp->AddVertexShaderReplacement(
"//VTK::Normal::Dec", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Dec\n" // we still want the default
" out vec4 myVertexMC;\n",
false // only do it once
);
#else
mapper->AddShaderReplacement(
vtkShader::Vertex,
"//VTK::Normal::Dec", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Dec\n" // we still want the default
" out vec4 myVertexMC;\n",
false // only do it once
);
#endif
#if USE_SHADER_PROPERTIES
sp->AddVertexShaderReplacement(
"//VTK::Normal::Impl", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Impl\n" // we still want the default
" myVertexMC = vertexMC;\n",
false // only do it once
);
#else
mapper->AddShaderReplacement(
vtkShader::Vertex,
"//VTK::Normal::Impl", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Impl\n" // we still want the default
" myVertexMC = vertexMC;\n",
false // only do it once
);
#endif
// Add the code to generate noise
// These functions need to be defined outside of main. Use the System::Dec
// to declare and implement
#if USE_SHADER_PROPERTIES
sp->AddFragmentShaderReplacement("//VTK::System::Dec",
false, // before the standard replacements
shaderCode.str(),
false // only do it once
);
#else
mapper->AddShaderReplacement(vtkShader::Fragment, "//VTK::System::Dec",
false, // before the standard replacements
shaderCode.str(),
false // only do it once
);
#endif
// Define varying and uniforms for the fragment shader here
#if USE_SHADER_PROPERTIES
sp->AddFragmentShaderReplacement(
"//VTK::Normal::Dec", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Dec\n" // we still want the default
" varying vec4 myVertexMC;\n"
" uniform vec3 veincolor = vec3(1.0, 1.0, 1.0);\n"
" uniform float veinfreq = 10.0;\n"
" uniform int veinlevels = 2;\n"
" uniform float warpfreq = 1;\n"
" uniform float warping = .5;\n"
" uniform float sharpness = 8.0;\n",
false // only do it once
);
#else
mapper->AddShaderReplacement(
vtkShader::Fragment, // in the fragment shader
"//VTK::Normal::Dec", // replace the normal block
true, // before the standard replacements
"//VTK::Normal::Dec\n" // we still want the default
" varying vec4 myVertexMC;\n"
" uniform vec3 veincolor = vec3(1.0, 1.0, 1.0);\n"
" uniform float veinfreq = 10.0;\n"
" uniform int veinlevels = 2;\n"
" uniform float warpfreq = 1;\n"
" uniform float warping = .5;\n"
" uniform float sharpness = 8.0;\n",
false // only do it once
);
#endif
#if USE_SHADER_PROPERTIES
sp->AddFragmentShaderReplacement(
"//VTK::Light::Impl", // replace the light block
false, // after the standard replacements
"//VTK::Light::Impl\n" // we still want the default calc
"\n"
"#define pnoise(x) ((noise(x) + 1.0) / 2.0)\n"
"#define snoise(x) (2.0 * pnoise(x) - 1.0)\n"
" vec3 Ct;\n"
" int i;\n"
" float turb, freq;\n"
" float turbsum;\n"
" /* perturb the lookup */\n"
" freq = 1.0;\n"
" vec4 offset = vec4(0.0,0.0,0.0,0.0);\n"
" vec4 noisyPoint;\n"
" vec4 myLocalVertexMC = myVertexMC;\n"
"\n"
" for (i = 0; i < 6; i += 1) {\n"
" noisyPoint[0] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[1] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[2] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[3] = 1.0;\n"
" offset += 2.0 * warping * (noisyPoint - 0.5) / freq;\n"
" freq *= 2.0;\n"
" }\n"
" myLocalVertexMC.x += offset.x;\n"
" myLocalVertexMC.y += offset.y;\n"
" myLocalVertexMC.z += offset.z;\n"
"\n"
" /* Now calculate the veining function for the lookup area */\n"
" turbsum = 0.0; freq = 1.0;\n"
" myLocalVertexMC *= veinfreq;\n"
" for (i = 0; i < veinlevels; i += 1) {\n"
" turb = abs (snoise (myLocalVertexMC));\n"
" turb = pow (smoothstep (0.8, 1.0, 1.0 - turb), sharpness) / "
"freq;\n"
" turbsum += (1.0-turbsum) * turb;\n"
" freq *= 1.5;\n"
" myLocalVertexMC *= 1.5;\n"
" }\n"
"\n"
" Ct = mix (diffuseColor, veincolor, turbsum);\n"
"\n"
" fragOutput0.rgb = opacity * (ambientColor + Ct + specular);\n"
" fragOutput0.a = opacity;\n",
false // only do it once
);
#else
mapper->AddShaderReplacement(
vtkShader::Fragment, // in the fragment shader
"//VTK::Light::Impl", // replace the light block
false, // after the standard replacements
"//VTK::Light::Impl\n" // we still want the default calc
"\n"
"#define pnoise(x) ((noise(x) + 1.0) / 2.0)\n"
"#define snoise(x) (2.0 * pnoise(x) - 1.0)\n"
" vec3 Ct;\n"
" int i;\n"
" float turb, freq;\n"
" float turbsum;\n"
" /* perturb the lookup */\n"
" freq = 1.0;\n"
" vec4 offset = vec4(0.0,0.0,0.0,0.0);\n"
" vec4 noisyPoint;\n"
" vec4 myLocalVertexMC = myVertexMC;\n"
"\n"
" for (i = 0; i < 6; i += 1) {\n"
" noisyPoint[0] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[1] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[2] = snoise(warpfreq * freq * myLocalVertexMC);\n"
" noisyPoint[3] = 1.0;\n"
" offset += 2.0 * warping * (noisyPoint - 0.5) / freq;\n"
" freq *= 2.0;\n"
" }\n"
" myLocalVertexMC.x += offset.x;\n"
" myLocalVertexMC.y += offset.y;\n"
" myLocalVertexMC.z += offset.z;\n"
"\n"
" /* Now calculate the veining function for the lookup area */\n"
" turbsum = 0.0; freq = 1.0;\n"
" myLocalVertexMC *= veinfreq;\n"
" for (i = 0; i < veinlevels; i += 1) {\n"
" turb = abs (snoise (myLocalVertexMC));\n"
" turb = pow (smoothstep (0.8, 1.0, 1.0 - turb), sharpness) / "
"freq;\n"
" turbsum += (1.0-turbsum) * turb;\n"
" freq *= 1.5;\n"
" myLocalVertexMC *= 1.5;\n"
" }\n"
"\n"
" Ct = mix (diffuseColor, veincolor, turbsum);\n"
"\n"
" fragOutput0.rgb = opacity * (ambientColor + Ct + specular);\n"
" fragOutput0.a = opacity;\n",
false // only do it once
);
#endif
vtkNew<ShaderCallback> myCallback;
myCallback->Renderer = renderer;
if (argc == 6)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
}
if (argc == 7)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
myCallback->veinfreq = atof(argv[6]);
}
if (argc == 8)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
myCallback->veinfreq = atof(argv[6]);
myCallback->veinlevels = atoi(argv[7]);
}
if (argc == 9)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
myCallback->veinfreq = atof(argv[6]);
myCallback->veinlevels = atoi(argv[7]);
myCallback->warpfreq = atof(argv[8]);
}
if (argc == 10)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
myCallback->veinfreq = atof(argv[6]);
myCallback->veinlevels = atoi(argv[7]);
myCallback->warpfreq = atof(argv[8]);
myCallback->warping = atof(argv[9]);
}
if (argc == 11)
{
myCallback->veincolor[0] = atof(argv[3]);
myCallback->veincolor[1] = atof(argv[4]);
myCallback->veincolor[2] = atof(argv[5]);
myCallback->veinfreq = atof(argv[6]);
myCallback->veinlevels = atoi(argv[7]);
myCallback->warpfreq = atof(argv[8]);
myCallback->warping = atof(argv[9]);
myCallback->sharpness = atof(argv[10]);
}
std::cout << "Input: " << (argc > 2 ? argv[2] : "Generated Sphere")
<< std::endl;
myCallback->Print(std::cout);
mapper->AddObserver(vtkCommand::UpdateShaderEvent, myCallback);
renderWindow->Render();
renderer->GetActiveCamera()->SetPosition(-.3, 0, .08);
renderer->GetActiveCamera()->SetFocalPoint(0, 0, 0);
renderer->GetActiveCamera()->SetViewUp(.26, 0.0, .96);
renderer->ResetCamera();
renderer->GetActiveCamera()->Zoom(1.5);
renderWindow->Render();
renderWindow->SetWindowName("MarbleShader");
renderWindow->Render();
interactor->Start();
transform->GetOutput()->GetBounds(bounds);
std::cout << "Range: "
<< " x " << bounds[1] - bounds[0] << " y " << bounds[3] - bounds[2]
<< " y " << bounds[5] - bounds[4] << std::endl;
return EXIT_SUCCESS;
}
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(const char* fileName)
{
vtkSmartPointer<vtkPolyData> polyData;
std::string extension =
vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
if (extension == ".ply")
{
vtkNew<vtkPLYReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".vtp")
{
vtkNew<vtkXMLPolyDataReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".obj")
{
vtkNew<vtkOBJReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".stl")
{
vtkNew<vtkSTLReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".vtk")
{
vtkNew<vtkPolyDataReader> reader;
reader->SetFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else if (extension == ".g")
{
vtkNew<vtkBYUReader> reader;
reader->SetGeometryFileName(fileName);
reader->Update();
polyData = reader->GetOutput();
}
else
{
vtkNew<vtkSphereSource> source;
source->SetPhiResolution(25);
source->SetThetaResolution(25);
source->Update();
polyData = source->GetOutput();
}
return polyData;
}
} // namespace
CMakeLists.txt¶
cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
project(MarbleShader)
find_package(VTK COMPONENTS
)
if (NOT VTK_FOUND)
message(FATAL_ERROR "MarbleShader: Unable to find the VTK build folder.")
endif()
# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(MarbleShader MACOSX_BUNDLE MarbleShader.cxx )
target_link_libraries(MarbleShader PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
TARGETS MarbleShader
MODULES ${VTK_LIBRARIES}
)
Download and Build MarbleShader¶
Click here to download MarbleShader and its CMakeLists.txt file. Once the tarball MarbleShader.tar has been downloaded and extracted,
cd MarbleShader/build
If VTK is installed:
cmake ..
If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
Build the project:
make
and run it:
./MarbleShader
WINDOWS USERS
Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.