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pycvc_gl: render_png_camera — offscreen render with an explicit camera #159

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Merged
transfix merged 2 commits into from
Jul 26, 2026
Merged

pycvc_gl: render_png_camera — offscreen render with an explicit camera #159

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5bcf7e0
pycvc_gl: render_png_camera — offscreen render with an explicit camera
Jul 26, 2026
c2053b6
pycvc_gl: clang-format render_png_camera signatures
Jul 26, 2026
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33 changes: 33 additions & 0 deletions bindings/pycvc/pycvc_scene.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include <cvc/gl/SceneGraph.h>
#include <cvc/volume/bounding_box.h>
#include <stdexcept>
#include <vtkCamera.h>
#include <vtkNew.h>
#include <vtkPNGWriter.h>
#include <vtkProp.h>
Expand Down Expand Up @@ -75,6 +76,38 @@ void render_png(SceneGraph &sg, const std::string &path, int width, int height)
window->Finalize();
}

void render_png_camera(SceneGraph &sg, const std::string &path, int width, int height, double eye_x,
double eye_y, double eye_z, double focal_x, double focal_y, double focal_z,
double up_x, double up_y, double up_z, double view_angle, double clip_near,
double clip_far) {
// Like render_png, but sets an EXPLICIT camera (eye / focal / up + view angle +
// clip range) instead of ResetCamera() — so a caller can script a chase camera
// for frame-by-frame offscreen capture. Needs a GL context (offscreen is fine).
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> window;
window->SetOffScreenRendering(1);
window->AddRenderer(renderer);
window->SetSize(width, height);
sg.setRenderer(renderer);
sg.processEvents();
vtkCamera *cam = renderer->GetActiveCamera();
cam->SetPosition(eye_x, eye_y, eye_z);
cam->SetFocalPoint(focal_x, focal_y, focal_z);
cam->SetViewUp(up_x, up_y, up_z);
cam->SetViewAngle(view_angle);
cam->SetClippingRange(clip_near, clip_far);
window->Render();
vtkNew<vtkWindowToImageFilter> w2i;
w2i->SetInput(window);
w2i->Update();
vtkNew<vtkPNGWriter> writer;
writer->SetFileName(path.c_str());
writer->SetInputConnection(w2i->GetOutputPort());
writer->Write();
sg.setRenderer(nullptr);
window->Finalize();
}

void show(SceneGraph &sg, const std::string &title, int width, int height) {
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> window;
Expand Down
8 changes: 8 additions & 0 deletions bindings/pycvc/pycvc_scene.h
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Expand Up @@ -28,6 +28,14 @@ namespace pycvc {
// events + frames the camera first. Needs a GL context (offscreen is fine).
void render_png(SceneGraph &sg, const std::string &path, int width = 1024, int height = 768);

// Render one offscreen frame with an EXPLICIT camera (eye / focal-point / up +
// view angle + clip range) instead of auto-framing — for scripting a chase camera
// across a sequence of frames (e.g. capturing a drive to video). Offscreen is fine.
void render_png_camera(SceneGraph &sg, const std::string &path, int width, int height, double eye_x,
double eye_y, double eye_z, double focal_x, double focal_y, double focal_z,
double up_x, double up_y, double up_z, double view_angle = 30.0,
double clip_near = 1.0, double clip_far = 1e5);

// Open a blocking interactive window on `sg` (needs a display); returns when the
// window closes. Don't call this in the embedded case — the host owns the loop.
void show(SceneGraph &sg, const std::string &title = "pycvc_gl", int width = 1024,
Expand Down
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