make scaled_principal_point_offset an opaque instance variable to pre…

…vent new drjit kernel from being generated on every iteration when film parameters are changed; fix mitsuba-renderer#908

src/sensors/perspective.cpp

@@ -190,9 +190,9 @@ class PerspectiveCamera final : public ProjectiveCamera<Float, Spectrum> {
         m_image_rect.expand(Point2f(pmax.x(), pmax.y()) / pmax.z());
         m_normalization = 1.f / m_image_rect.volume();
         m_needs_sample_3 = false;
-
+	m_scaled_principal_point_offset = m_film->size() * m_principal_point_offset / m_film->crop_size();
         dr::make_opaque(m_camera_to_sample, m_sample_to_camera, m_dx, m_dy, m_x_fov,
-                        m_image_rect, m_normalization, m_principal_point_offset);
+                        m_image_rect, m_normalization, m_principal_point_offset, m_scaled_principal_point_offset);
     }
 
     std::pair<Ray3f, Spectrum> sample_ray(Float time, Float wavelength_sample,
@@ -209,13 +209,10 @@ class PerspectiveCamera final : public ProjectiveCamera<Float, Spectrum> {
         ray.time = time;
         ray.wavelengths = wavelengths;
 
-        Vector2f scaled_principal_point_offset =
-            m_film->size() * m_principal_point_offset / m_film->crop_size();
-
         // Compute the sample position on the near plane (local camera space).
         Point3f near_p = m_sample_to_camera *
-                         Point3f(position_sample.x() + scaled_principal_point_offset.x(),
-                                 position_sample.y() + scaled_principal_point_offset.y(),
+                         Point3f(position_sample.x() + m_scaled_principal_point_offset.x(),
+                                 position_sample.y() + m_scaled_principal_point_offset.y(),
                                  0.f);
 
         // Convert into a normalized ray direction; adjust the ray interval accordingly.
@@ -246,13 +243,10 @@ class PerspectiveCamera final : public ProjectiveCamera<Float, Spectrum> {
         ray.time = time;
         ray.wavelengths = wavelengths;
 
-        Vector2f scaled_principal_point_offset =
-            m_film->size() * m_principal_point_offset / m_film->crop_size();
-
         // Compute the sample position on the near plane (local camera space).
         Point3f near_p = m_sample_to_camera *
-                         Point3f(position_sample.x() + scaled_principal_point_offset.x(),
-                                 position_sample.y() + scaled_principal_point_offset.y(),
+                         Point3f(position_sample.x() + m_scaled_principal_point_offset.x(),
+                                 position_sample.y() + m_scaled_principal_point_offset.y(),
                                  0.f);
 
         // Convert into a normalized ray direction; adjust the ray interval accordingly.
@@ -290,12 +284,9 @@ class PerspectiveCamera final : public ProjectiveCamera<Float, Spectrum> {
         if (dr::none_or<false>(active))
             return { ds, dr::zeros<Spectrum>() };
 
-        Vector2f scaled_principal_point_offset =
-            m_film->size() * m_principal_point_offset / m_film->crop_size();
-
         Point3f screen_sample = m_camera_to_sample * ref_p;
-        ds.uv = Point2f(screen_sample.x() - scaled_principal_point_offset.x(),
-                        screen_sample.y() - scaled_principal_point_offset.y());
+        ds.uv = Point2f(screen_sample.x() - m_scaled_principal_point_offset.x(),
+                        screen_sample.y() - m_scaled_principal_point_offset.y());
         active &= (ds.uv.x() >= 0) && (ds.uv.x() <= 1) && (ds.uv.y() >= 0) &&
                   (ds.uv.y() <= 1);
         if (dr::none_or<false>(active))
@@ -409,6 +400,7 @@ class PerspectiveCamera final : public ProjectiveCamera<Float, Spectrum> {
     Float m_x_fov;
     Vector3f m_dx, m_dy;
     Vector2f m_principal_point_offset;
+    Vector2f m_scaled_principal_point_offset;
 };
 
 MI_IMPLEMENT_CLASS_VARIANT(PerspectiveCamera, ProjectiveCamera)