Export POVray animations (demo_POST_povray.cpp)

Tutorial that teaches how to use the POSTPROCESS module to create animations with POVray.

When the simulation is run, a set of .pov and .ini files are saved on disk, so that one can use POVray later to do high-quality rendering of simulations.

• Learn how to attach chrono::ChVisualShape to rigid bodies.
• Learn how to output data for POVray.

Note: the same assets can be used to render animations in real-time in the interactive 3D view of Irrlicht, as explained in demo_IRR_assets.cpp

Example 1

Create a chrono::ChBody, and attach some 'assets' that define 3D shapes. These shapes can be shown by Irrlicht, OpenGL, or POV postprocessing. Note: these assets are independent from collision shapes.

 
    // Create a ChBody, and attach some 'assets'
    // that define 3D shapes. These shapes can be shown
    // by Irrlicht or POV postprocessing, etc...
    // Note: these assets are independent from collision shapes!
 
    // Create a rigid body as usual, and add it
    // to the physical system:
    auto floor = chrono_types::make_shared<ChBody>();
    floor->SetBodyFixed(true);
 
    // Define a collision shape
    auto floor_mat = chrono_types::make_shared<ChMaterialSurfaceNSC>();
 
    floor->GetCollisionModel()->ClearModel();
    floor->GetCollisionModel()->AddBox(floor_mat, 10, 0.5, 10, ChVector<>(0, -1, 0));
    floor->GetCollisionModel()->BuildModel();
    floor->SetCollide(true);
 
    // Add body to system
    sys.Add(floor);
 
    // ==Asset== attach a 'box' shape.
    auto boxfloor = chrono_types::make_shared<ChBoxShape>();
    boxfloor->GetBoxGeometry().Size = ChVector<>(10, 0.5, 10);
    boxfloor->SetColor(ChColor(0.3f, 0.3f, 0.6f));
    floor->AddVisualShape(boxfloor, ChFrame<>(ChVector<>(0, -1, 0)));
 

Example 2

Textures, colors, asset levels with transformations. This section shows how to add more advanced types of assets.

 
    // Textures, colors, asset levels with transformations.
 
    // Create the rigid body as usual (this won't move, it is only for visualization tests)
    auto body = chrono_types::make_shared<ChBody>();
    body->SetBodyFixed(true);
    sys.Add(body);
 
    // ==Asset== Attach a 'sphere' shape
    auto sphere = chrono_types::make_shared<ChSphereShape>();
    sphere->GetSphereGeometry().rad = 0.5;
    body->AddVisualShape(sphere, ChFrame<>(ChVector<>(-1, 0, 0)));
 
    // ==Asset== Attach also a 'box' shape
    auto mbox = chrono_types::make_shared<ChBoxShape>();
    mbox->GetBoxGeometry().Size = ChVector<>(0.2, 0.5, 0.1);
    body->AddVisualShape(mbox, ChFrame<>(ChVector<>(1, 0, 0)));
 
    // ==Asset== Attach also a 'cylinder' shape
    auto cyl = chrono_types::make_shared<ChCylinderShape>();
    cyl->GetCylinderGeometry().p1 = ChVector<>(2, -0.2, 0);
    cyl->GetCylinderGeometry().p2 = ChVector<>(2.2, 0.5, 0);
    cyl->GetCylinderGeometry().rad = 0.3;
    body->AddVisualShape(cyl);
 
    // ==Asset== Attach a 'Wavefront mesh' asset, referencing a .obj file:
    auto objmesh = chrono_types::make_shared<ChObjFileShape>();
    objmesh->SetFilename(GetChronoDataFile("models/forklift/body.obj"));
    objmesh->SetTexture(GetChronoDataFile("textures/bluewhite.png"));
    body->AddVisualShape(objmesh, ChFrame<>(ChVector<>(0, 0, 2)));
 
    // ==Asset== Attach an array of boxes, each rotated to make a spiral
    for (int j = 0; j < 20; j++) {
        auto smallbox = chrono_types::make_shared<ChBoxShape>();
        smallbox->GetBoxGeometry().Size = ChVector<>(0.1, 0.1, 0.01);
        smallbox->SetColor(ChColor(j * 0.05f, 1 - j * 0.05f, 0.0f));
        ChMatrix33<> rot(Q_from_AngY(j * 21 * CH_C_DEG_TO_RAD));
        ChVector<> pos = rot * ChVector<>(0.4, 0, 0) + ChVector<>(0, j * 0.02, 0);
        body->AddVisualShape(smallbox, ChFrame<>(pos, rot));
    }
 
    // ==Asset== Attach a video camera.
    // Note that a camera can also be attached to a moving object.
    auto camera = chrono_types::make_shared<ChCamera>();
    camera->SetAngle(50);
    camera->SetPosition(ChVector<>(-3, 4, -5));
    camera->SetAimPoint(ChVector<>(0, 1, 0));
    body->AddCamera(camera);
 

Example 3

Create a chrono::ChParticleCloud cluster, and attach 'assets' that define a single "sample" 3D shape. This will be shown N times in POV or Irrlicht.

 
    // Create a ChParticleClones cluster, and attach 'assets'
    // that define a single "sample" 3D shape. This will be shown
    // N times in Irrlicht.
 
    // Create the ChParticleClones, populate it with some random particles,
    // and add it to physical system:
    auto particles = chrono_types::make_shared<ChParticleCloud>();
 
    // Note: coll. shape, if needed, must be specified before creating particles
    auto particle_mat = chrono_types::make_shared<ChMaterialSurfaceNSC>();
 
    particles->GetCollisionModel()->ClearModel();
    particles->GetCollisionModel()->AddSphere(particle_mat, 0.05);
    particles->GetCollisionModel()->BuildModel();
    particles->SetCollide(true);
 
    // Create the random particles
    for (int np = 0; np < 100; ++np)
        particles->AddParticle(ChCoordsys<>(ChVector<>(ChRandom() - 2, 1, ChRandom() - 0.5)));
 
    // Do not forget to add the particle cluster to the system:
    sys.Add(particles);
 
    //  ==Asset== Attach a 'sphere' shape asset.. it will be used as a sample
    // shape to display all particles when rendering in 3D!
    auto sphereparticle = chrono_types::make_shared<ChSphereShape>();
    sphereparticle->GetSphereGeometry().rad = 0.05;
    particles->AddVisualShape(sphereparticle);
 

The POV exporter

The following part is very important because this is what makes this demo different from the demo_IRR_assets, that used Irrlicht. We need to create a postprocessor of type chrono::postprocess::ChPovRay and tell him that we are going to export our visualization assets:

 
    // Create an exporter to POVray
    ChPovRay pov_exporter = ChPovRay(&sys);
 
    // Important: set the path to the template:
    pov_exporter.SetTemplateFile(GetChronoDataFile("POVRay_chrono_template.pov"));
 
    // Set the path where it will save all .pov, .ini, .asset and .dat files, a directory will be created if not
    // existing
    pov_exporter.SetBasePath(GetChronoOutputPath() + "POVRAY_1");
 
    // Optional: change the default naming of the generated files:
    // pov_exporter.SetOutputScriptFile("rendering_frames.pov");
    // pov_exporter.SetOutputDataFilebase("my_state");
    // pov_exporter.SetPictureFilebase("picture");
 
    // --Optional: modify default light
    pov_exporter.SetLight(ChVector<>(-3, 4, 2), ChColor(0.15f, 0.15f, 0.12f), false);
 
    // --Optional: add further POV commands, for example in this case:
    //     create an area light for soft shadows
    //     create a Grid object; Grid() parameters: step, linewidth, linecolor, planecolor
    //   Remember to use \ at the end of each line for a multiple-line string.
    pov_exporter.SetCustomPOVcommandsScript(
        " \
    light_source {   \
      <2, 10, -3>  \
      color rgb<1.2,1.2,1.2> \
      area_light <4, 0, 0>, <0, 0, 4>, 8, 8 \
      adaptive 1 \
      jitter\
    } \
    object{ Grid(1,0.02, rgb<0.7,0.8,0.8>, rgbt<1,1,1,1>) rotate <0, 0, 90>  } \
    ");
 

The simulation loop

Now you have to write the usual while() loop to perform the simulation. Note that before running the loop you need to use pov_exporter.ExportScript(); , and for each timestep you must use pov_exporter.ExportData(); actually this is the instruction that creates the many .dat and .pov files in the output directory.

 
    //
    // RUN THE SIMULATION AND SAVE THE POVray FILES AT EACH FRAME
    //
 
    // 1) Create the two .pov and .ini files for POV-Ray (this must be done
    //    only once at the beginning of the simulation).
 
    pov_exporter.ExportScript();
 
    while (sys.GetChTime() < 1.5) {
        sys.DoStepDynamics(0.01);
 
        GetLog() << "time= " << sys.GetChTime() << "\n";
 
        // 2) Create the incremental nnnn.dat and nnnn.pov files that will be load
        //    by the pov .ini script in POV-Ray (do this at each simulation timestep)
        pov_exporter.ExportData();
    }
 
    // That's all! If all worked ok, this python script should
    // have created a  "rendering_frames.pov.ini"  file that you can
    // load in POV-Ray, then when you press 'RUN' you will see that
    // POV-Ray will start rendering a short animation, saving the frames
    // in the directory 'anim'.
 

Executing and rendering with POVray

Once you created your program, compile it, then:

• execute the demo_POST_povray1.exe
• on the console you will see a time counter showing that the system is load and it is being simulated
• when the program ends, you must open POVray and open the rendering_frames.pov.ini file, using the Open menu or button, or drag&drop (you can find this .ini file and other POVray as they are saved in the same directory of the executable)

• press the Run button in POVray to execute the .ini file , and you should see that POVray generates lot of frames, being saved in the directory anim.

Optional encoding into an AVI or MPEG animation

If you want to generate a .mpeg or .avi animation from the rendered .bmp images, we suggest to use the VirtualDub tool:

• drag&drop the first .jpg frame in its interface; it will automatically load all other frames in the timeline
• use menu Video/Compression... to setup the proper video codec (suggested: Xvid, DivX, mpeg4, etc.)
• use menu File/Save As Avi... to encode and save the animation on disk.

Listing

In the following we report the entire source code for reference.

// =============================================================================
// PROJECT CHRONO - http://projectchrono.org
//
// Copyright (c) 2014 projectchrono.org
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file at the top level of the distribution and at
// http://projectchrono.org/license-chrono.txt.
//
// =============================================================================
// Authors: Alessandro Tasora
// =============================================================================
//
// Demo code about using the assets system to create shapes that can be shown in
// the 3D postprocessing, by using POVray.
//
// =============================================================================
 
#include "chrono/assets/ChBoxShape.h"
#include "chrono/assets/ChCamera.h"
#include "chrono/assets/ChCylinderShape.h"
#include "chrono/assets/ChObjFileShape.h"
#include "chrono/assets/ChSphereShape.h"
#include "chrono/assets/ChTexture.h"
#include "chrono/physics/ChParticleCloud.h"
#include "chrono/physics/ChSystemNSC.h"
 
#include "chrono_postprocess/ChPovRay.h"
 
#include "chrono_thirdparty/filesystem/path.h"
 
using namespace chrono;
using namespace postprocess;
 
int main(int argc, char* argv[]) {
    GetLog() << "Copyright (c) 2017 projectchrono.org\nChrono version: " << CHRONO_VERSION << "\n\n";
 
    // Create a Chrono::Engine physical system
    ChSystemNSC sys;
 
    /* Start example */
 
    // Create an exporter to POVray
    ChPovRay pov_exporter = ChPovRay(&sys);
 
    // Important: set the path to the template:
    pov_exporter.SetTemplateFile(GetChronoDataFile("POVRay_chrono_template.pov"));
 
    // Set the path where it will save all .pov, .ini, .asset and .dat files, a directory will be created if not
    // existing
    pov_exporter.SetBasePath(GetChronoOutputPath() + "POVRAY_1");
 
    // Optional: change the default naming of the generated files:
    // pov_exporter.SetOutputScriptFile("rendering_frames.pov");
    // pov_exporter.SetOutputDataFilebase("my_state");
    // pov_exporter.SetPictureFilebase("picture");
 
    // --Optional: modify default light
    pov_exporter.SetLight(ChVector<>(-3, 4, 2), ChColor(0.15f, 0.15f, 0.12f), false);
 
    // --Optional: add further POV commands, for example in this case:
    //     create an area light for soft shadows
    //     create a Grid object; Grid() parameters: step, linewidth, linecolor, planecolor
    //   Remember to use \ at the end of each line for a multiple-line string.
    pov_exporter.SetCustomPOVcommandsScript(
        " \
    light_source {   \
      <2, 10, -3>  \
      color rgb<1.2,1.2,1.2> \
      area_light <4, 0, 0>, <0, 0, 4>, 8, 8 \
      adaptive 1 \
      jitter\
    } \
    object{ Grid(1,0.02, rgb<0.7,0.8,0.8>, rgbt<1,1,1,1>) rotate <0, 0, 90>  } \
    ");
 
    /* End example */
 
    /* Start example */
 
    // Create a ChBody, and attach some 'assets'
    // that define 3D shapes. These shapes can be shown
    // by Irrlicht or POV postprocessing, etc...
    // Note: these assets are independent from collision shapes!
 
    // Create a rigid body as usual, and add it
    // to the physical system:
    auto floor = chrono_types::make_shared<ChBody>();
    floor->SetBodyFixed(true);
 
    // Define a collision shape
    auto floor_mat = chrono_types::make_shared<ChMaterialSurfaceNSC>();
 
    floor->GetCollisionModel()->ClearModel();
    floor->GetCollisionModel()->AddBox(floor_mat, 10, 0.5, 10, ChVector<>(0, -1, 0));
    floor->GetCollisionModel()->BuildModel();
    floor->SetCollide(true);
 
    // Add body to system
    sys.Add(floor);
 
    // ==Asset== attach a 'box' shape.
    auto boxfloor = chrono_types::make_shared<ChBoxShape>();
    boxfloor->GetBoxGeometry().Size = ChVector<>(10, 0.5, 10);
    boxfloor->SetColor(ChColor(0.3f, 0.3f, 0.6f));
    floor->AddVisualShape(boxfloor, ChFrame<>(ChVector<>(0, -1, 0)));
 
    /* End example */
 
    /* Start example */
 
    // Textures, colors, asset levels with transformations.
 
    // Create the rigid body as usual (this won't move, it is only for visualization tests)
    auto body = chrono_types::make_shared<ChBody>();
    body->SetBodyFixed(true);
    sys.Add(body);
 
    // ==Asset== Attach a 'sphere' shape
    auto sphere = chrono_types::make_shared<ChSphereShape>();
    sphere->GetSphereGeometry().rad = 0.5;
    body->AddVisualShape(sphere, ChFrame<>(ChVector<>(-1, 0, 0)));
 
    // ==Asset== Attach also a 'box' shape
    auto mbox = chrono_types::make_shared<ChBoxShape>();
    mbox->GetBoxGeometry().Size = ChVector<>(0.2, 0.5, 0.1);
    body->AddVisualShape(mbox, ChFrame<>(ChVector<>(1, 0, 0)));
 
    // ==Asset== Attach also a 'cylinder' shape
    auto cyl = chrono_types::make_shared<ChCylinderShape>();
    cyl->GetCylinderGeometry().p1 = ChVector<>(2, -0.2, 0);
    cyl->GetCylinderGeometry().p2 = ChVector<>(2.2, 0.5, 0);
    cyl->GetCylinderGeometry().rad = 0.3;
    body->AddVisualShape(cyl);
 
    // ==Asset== Attach a 'Wavefront mesh' asset, referencing a .obj file:
    auto objmesh = chrono_types::make_shared<ChObjFileShape>();
    objmesh->SetFilename(GetChronoDataFile("models/forklift/body.obj"));
    objmesh->SetTexture(GetChronoDataFile("textures/bluewhite.png"));
    body->AddVisualShape(objmesh, ChFrame<>(ChVector<>(0, 0, 2)));
 
    // ==Asset== Attach an array of boxes, each rotated to make a spiral
    for (int j = 0; j < 20; j++) {
        auto smallbox = chrono_types::make_shared<ChBoxShape>();
        smallbox->GetBoxGeometry().Size = ChVector<>(0.1, 0.1, 0.01);
        smallbox->SetColor(ChColor(j * 0.05f, 1 - j * 0.05f, 0.0f));
        ChMatrix33<> rot(Q_from_AngY(j * 21 * CH_C_DEG_TO_RAD));
        ChVector<> pos = rot * ChVector<>(0.4, 0, 0) + ChVector<>(0, j * 0.02, 0);
        body->AddVisualShape(smallbox, ChFrame<>(pos, rot));
    }
 
    // ==Asset== Attach a video camera.
    // Note that a camera can also be attached to a moving object.
    auto camera = chrono_types::make_shared<ChCamera>();
    camera->SetAngle(50);
    camera->SetPosition(ChVector<>(-3, 4, -5));
    camera->SetAimPoint(ChVector<>(0, 1, 0));
    body->AddCamera(camera);
 
    /* End example */
 
    /* Start example */
 
    // Create a ChParticleClones cluster, and attach 'assets'
    // that define a single "sample" 3D shape. This will be shown
    // N times in Irrlicht.
 
    // Create the ChParticleClones, populate it with some random particles,
    // and add it to physical system:
    auto particles = chrono_types::make_shared<ChParticleCloud>();
 
    // Note: coll. shape, if needed, must be specified before creating particles
    auto particle_mat = chrono_types::make_shared<ChMaterialSurfaceNSC>();
 
    particles->GetCollisionModel()->ClearModel();
    particles->GetCollisionModel()->AddSphere(particle_mat, 0.05);
    particles->GetCollisionModel()->BuildModel();
    particles->SetCollide(true);
 
    // Create the random particles
    for (int np = 0; np < 100; ++np)
        particles->AddParticle(ChCoordsys<>(ChVector<>(ChRandom() - 2, 1, ChRandom() - 0.5)));
 
    // Do not forget to add the particle cluster to the system:
    sys.Add(particles);
 
    //  ==Asset== Attach a 'sphere' shape asset.. it will be used as a sample
    // shape to display all particles when rendering in 3D!
    auto sphereparticle = chrono_types::make_shared<ChSphereShape>();
    sphereparticle->GetSphereGeometry().rad = 0.05;
    particles->AddVisualShape(sphereparticle);
 
    /* End example */
 
    // Export all existing visual shapes to POV-Ray
    pov_exporter.AddAll();
 
    // (Optional: tell selectively which physical items you
    // want to render in the folllowing way...)
    //  pov_exporter.RemoveAll();
    //  pov_exporter.Add(floor);
    //  pov_exporter.Add(body);
    //  pov_exporter.Add(particles);
 
    /* Start example */
 
    //
    // RUN THE SIMULATION AND SAVE THE POVray FILES AT EACH FRAME
    //
 
    // 1) Create the two .pov and .ini files for POV-Ray (this must be done
    //    only once at the beginning of the simulation).
 
    pov_exporter.ExportScript();
 
    while (sys.GetChTime() < 1.5) {
        sys.DoStepDynamics(0.01);
 
        GetLog() << "time= " << sys.GetChTime() << "\n";
 
        // 2) Create the incremental nnnn.dat and nnnn.pov files that will be load
        //    by the pov .ini script in POV-Ray (do this at each simulation timestep)
        pov_exporter.ExportData();
    }
 
    // That's all! If all worked ok, this python script should
    // have created a  "rendering_frames.pov.ini"  file that you can
    // load in POV-Ray, then when you press 'RUN' you will see that
    // POV-Ray will start rendering a short animation, saving the frames
    // in the directory 'anim'.
 
    /* End example */
 
    return 0;
}