Update APIs to use opaque handle types instead of concrete types.

PiperOrigin-RevId: 906895053
Change-Id: Id61d437ea814e038f25d92375eb747a6c6775c32

src/experimental/filament/filament/filament_context.cc

@@ -87,7 +87,7 @@ FilamentContext::FrameHandle FilamentContext::Render(
   }
 
   bool render_began = false;
-  RenderTarget* current_target = nullptr;
+  mjrRenderTarget* current_target = nullptr;
   for (const RenderRequest& request : requests) {
     if (request.target != current_target && render_began) {
       renderer_->endFrame();
@@ -126,7 +126,8 @@ FilamentContext::FrameHandle FilamentContext::Render(
         scene_view_request.draw_mode = request.draw_mode;
         scene_view_request.viewport = {0, 0, request.width, request.height};
         scene_view_request.camera = request.camera;
-        request.scene->Render(renderer_, scene_view_request);
+        SceneView* scene_view = SceneView::downcast(request.scene);
+        scene_view->Render(renderer_, scene_view_request);
       }
     } else {
       if (read_requests.empty()) {
@@ -146,13 +147,16 @@ FilamentContext::FrameHandle FilamentContext::Render(
         break;
       }
       if (render_began) {
+        RenderTarget* render_target = RenderTarget::downcast(request.target);
+
         SceneView::RenderRequest scene_view_request;
         scene_view_request.draw_mode = request.draw_mode;
         scene_view_request.viewport = {0, 0, request.width, request.height};
         scene_view_request.camera = request.camera;
-        scene_view_request.target = request.target;
+        scene_view_request.target = render_target;
-        request.scene->Render(renderer_, scene_view_request);
+        SceneView* scene_view = SceneView::downcast(request.scene);
-        request.target->ReadColorPixels(renderer_, read_request.output,
+        scene_view->Render(renderer_, scene_view_request);
+        render_target->ReadColorPixels(renderer_, read_request.output,
                                         read_request.num_bytes);
       }
     }

src/experimental/filament/filament/filament_context.h

@@ -35,15 +35,18 @@
 namespace mujoco {
 
 // Manages the filament renderer and provides APIs for rendering scenes.
-class FilamentContext {
+class FilamentContext : public mjrfContext {
  public:
   explicit FilamentContext(const mjrFilamentConfig* config);
   ~FilamentContext();
 
+  FilamentContext(const FilamentContext&) = delete;
+  FilamentContext& operator=(const FilamentContext&) = delete;
+
   // Information needed to render a single image of a scene.
   struct RenderRequest {
     // The scene to render.
-    SceneView* scene = nullptr;
+    mjrScene* scene = nullptr;
 
     // The method (e.g. Color, Depth, Segmentation, etc.) to use for rendering.
     DrawMode draw_mode = DrawMode::Color;
@@ -58,12 +61,12 @@ class FilamentContext {
     // The render target into which to render the image. If nullptr, the image
     // will be rendered to the window (as previously configured in
     // mjrFilamentConfig::native_window).
-    RenderTarget* target = nullptr;
+    mjrRenderTarget* target = nullptr;
   };
 
   // Information needed to read pixels from a render target.
   struct ReadPixelsRequest {
-    RenderTarget* target = nullptr;
+    mjrRenderTarget* target = nullptr;
 
     // The buffer into which the read pixels will be written.
     uint8_t* output = nullptr;
@@ -107,8 +110,12 @@ class FilamentContext {
 
   ObjectManager* GetObjectManager() const { return object_manager_.get(); }
 
-  FilamentContext(const FilamentContext&) = delete;
+  static FilamentContext* downcast(mjrfContext* context) {
-  FilamentContext& operator=(const FilamentContext&) = delete;
+    return static_cast<FilamentContext*>(context);
+  }
+  static const FilamentContext* downcast(const mjrfContext* context) {
+    return static_cast<const FilamentContext*>(context);
+  }
 
  private:
   mjrFilamentConfig config_;

src/experimental/filament/filament/light.cc

@@ -56,9 +56,10 @@ Light::Light(filament::Engine* engine, const mjrLightParams& params)
     filament::IndirectLight::Builder builder;
     if (params.texture) {
       // Allow null textures for fallback lights.
-      builder.reflections(params.texture->GetFilamentTexture());
+      const Texture* texture = Texture::downcast(params.texture);
+      builder.reflections(texture->GetFilamentTexture());
       const Texture::SphericalHarmonics* spherical_harmonics =
-          params.texture->GetSphericalHarmonics();
+          texture->GetSphericalHarmonics();
       if (spherical_harmonics != nullptr) {
         builder.irradiance(3, *spherical_harmonics);
       }

src/experimental/filament/filament/light.h

@@ -21,6 +21,7 @@
 #include <utils/Entity.h>
 #include <mujoco/mujoco.h>
 #include "experimental/filament/filament/texture.h"
+#include "experimental/filament/render_context_filament.h"
 
 namespace mujoco {
 
@@ -31,7 +32,7 @@ struct mjrLightParams {
   // The type of light (e.g. spot, point, directional, etc.)
   mjrLightType type;
   // The texture to use for image lights.
-  const Texture* texture;
+  const mjrTexture* texture;
   // The color of the light.
   float color[3];
   // The intensity of the light, in candela.
@@ -53,7 +54,7 @@ struct mjrLightParams {
 void mjr_defaultLightParams(mjrLightParams* params);
 
 // Manages the filament Entities for a single mjvLight.
-class Light {
+class Light : public mjrLight {
  public:
   Light(filament::Engine* engine, const mjrLightParams& params);
   ~Light() noexcept;
@@ -84,6 +85,13 @@ class Light {
   void Enable();
   void Disable();
 
+  static Light* downcast(mjrLight* light) {
+    return static_cast<Light*>(light);
+  }
+  static const Light* downcast(const mjrLight* light) {
+    return static_cast<const Light*>(light);
+  }
+
  private:
   filament::Engine* engine_ = nullptr;
   filament::IndirectLight* ibl_ = nullptr;

src/experimental/filament/filament/mesh.h

@@ -31,6 +31,7 @@
 #include <filament/VertexBuffer.h>
 #include <math/vec4.h>
 #include <mujoco/mujoco.h>
+#include "experimental/filament/render_context_filament.h"
 
 // Functions for creating filament vertex and index buffers.
 namespace mujoco {
@@ -138,13 +139,16 @@ struct mjrMeshData {
 void mjr_defaultMeshData(mjrMeshData* data);
 
 // Owns a Vertex and Index buffer representing a geometry mesh.
-class Mesh {
+class Mesh : public mjrMesh {
  public:
   // Creates a Mesh from the given MeshData.
   Mesh(filament::Engine* engine, const mjrMeshData& data);
 
   ~Mesh();
 
+  Mesh(const Mesh&) = delete;
+  Mesh& operator=(const Mesh&) = delete;
+
   // Returns the filament IndexBuffer for the mesh.
   filament::IndexBuffer* GetFilamentIndexBuffer() const;
 
@@ -163,8 +167,12 @@ class Mesh {
   // Returns the bounds of the mesh.
   filament::Box GetBounds() const;
 
-  Mesh(const Mesh&) = delete;
+  static Mesh* downcast(mjrMesh* mesh) {
-  Mesh& operator=(const Mesh&) = delete;
+    return static_cast<Mesh*>(mesh);
+  }
+  static const Mesh* downcast(const mjrMesh* mesh) {
+    return static_cast<const Mesh*>(mesh);
+  }
 
  private:
   void BuildVertexBuffer(const mjrMeshData& data);

src/experimental/filament/filament/render_target.h

@@ -22,6 +22,7 @@
 #include <filament/Engine.h>
 #include <filament/Texture.h>
 #include "experimental/filament/filament/texture.h"
+#include "experimental/filament/render_context_filament.h"
 
 namespace mujoco {
 
@@ -35,7 +36,7 @@ struct mjrRenderTargetConfig {
 void mjr_defaultRenderTargetConfig(mjrRenderTargetConfig* config);
 
 // Manages a filament RenderTarget and the textures which are bound to it.
-class RenderTarget {
+class RenderTarget : public mjrRenderTarget {
  public:
   // Defines the types of textures to create for the color and depth
   // attachments.
@@ -62,6 +63,13 @@ class RenderTarget {
   // Returns the underlying filament render target.
   filament::RenderTarget* GetFilamentRenderTarget() const;
 
+  static RenderTarget* downcast(mjrRenderTarget* render_target) {
+    return static_cast<RenderTarget*>(render_target);
+  }
+  static const RenderTarget* downcast(const mjrRenderTarget* render_target) {
+    return static_cast<const RenderTarget*>(render_target);
+  }
+
  private:
   void Destroy();
 

src/experimental/filament/filament/renderable.h

@@ -29,6 +29,7 @@
 #include "experimental/filament/filament/math_util.h"
 #include "experimental/filament/filament/mesh.h"
 #include "experimental/filament/filament/object_manager.h"
+#include "experimental/filament/render_context_filament.h"
 
 namespace mujoco {
 
@@ -61,7 +62,7 @@ void mjr_defaultRenderableParams(mjrRenderableParams* params);
 // the user specifies the MaterialParams and MaterialTextures to use with the
 // ShadingModel. Its these properties that ultimately define the actual material
 // of the Renderable.
-class Renderable {
+class Renderable : public mjrRenderable {
  public:
   // Default filament values for priority and layer mask.
   static constexpr std::uint8_t kDefaultPriority = 4;
@@ -139,6 +140,13 @@ class Renderable {
   // Returns the filament Engine managing the renderables.
   filament::Engine* GetEngine();
 
+  static Renderable* downcast(mjrRenderable* renderable) {
+    return static_cast<Renderable*>(renderable);
+  }
+  static const Renderable* downcast(const mjrRenderable* renderable) {
+    return static_cast<const Renderable*>(renderable);
+  }
+
  private:
   struct Part {
     utils::Entity entity;

src/experimental/filament/filament/scene_view.h

@@ -32,6 +32,7 @@
 #include "experimental/filament/filament/renderable.h"
 #include "experimental/filament/filament/render_target.h"
 #include "experimental/filament/filament/texture.h"
+#include "experimental/filament/render_context_filament.h"
 
 namespace mujoco {
 
@@ -40,11 +41,14 @@ namespace mujoco {
 // The filament Scene is populated with the objects (e.g. lights, renderables,
 // skybox, etc.). It manages multiple views to support a variety of draw modes
 // (e.g. normal, depth, segmentation, etc.) as well as reflective surfaces.
-class SceneView {
+class SceneView : public mjrScene {
  public:
   SceneView(filament::Engine* engine);
   ~SceneView();
 
+  SceneView(const SceneView&) = delete;
+  SceneView& operator=(const SceneView&) = delete;
+
   // Adds/removes entities from the scene.
   void AddToScene(Light* light);
   void RemoveFromScene(Light* light);
@@ -90,8 +94,12 @@ class SceneView {
   ColorGradingOptions GetColorGradingOptions() const;
   void SetColorGradingOptions(const ColorGradingOptions& opts);
 
-  SceneView(const SceneView&) = delete;
+  static SceneView* downcast(mjrScene* scene) {
-  SceneView& operator=(const SceneView&) = delete;
+    return static_cast<SceneView*>(scene);
+  }
+  static const SceneView* downcast(const mjrScene* scene) {
+    return static_cast<const SceneView*>(scene);
+  }
 
  private:
   // Marks a renderable as reflective. Reflective renderables have to be

src/experimental/filament/filament/texture.h

@@ -15,13 +15,12 @@
 #ifndef MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_TEXTURE_H_
 #define MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_TEXTURE_H_
 
-#include <cstddef>
-
 #include <filament/Engine.h>
 #include <filament/Texture.h>
 #include <math/vec3.h>
 #include <mujoco/mjmodel.h>
 #include <mujoco/mujoco.h>
+#include "experimental/filament/render_context_filament.h"
 
 // Functions for creating filament textures.
 namespace mujoco {
@@ -84,7 +83,7 @@ struct mjrTextureConfig {
 void mjr_defaultTextureConfig(mjrTextureConfig* config);
 
 // Wrapper around a filament::Texture.
-class Texture {
+class Texture : public mjrTexture {
  public:
   // Flags for internal use.
   struct InternalFlags {
@@ -99,6 +98,9 @@ class Texture {
 
   ~Texture();
 
+  Texture(const Texture&) = delete;
+  Texture& operator=(const Texture&) = delete;
+
   // Uploads the given data to the texture.
   void Upload(const mjrTextureData& data);
 
@@ -117,8 +119,12 @@ class Texture {
     return has_spherical_harmonics_ ? &spherical_harmonics_ : nullptr;
   }
 
-  Texture(const Texture&) = delete;
+  static Texture* downcast(mjrTexture* texture) {
-  Texture& operator=(const Texture&) = delete;
+    return static_cast<Texture*>(texture);
+  }
+  static const Texture* downcast(const mjrTexture* texture) {
+    return static_cast<const Texture*>(texture);
+  }
 
  private:
   void ReleaseData();

src/experimental/filament/render_context_filament.h

@@ -29,6 +29,17 @@ extern "C" {
 // IMPORTANT: This API should still be considered experimental and is likely
 // change frequently.
 
+// Opaque types.
+struct mjrTexture {};
+struct mjrMesh {};
+struct mjrScene {};
+struct mjrLight {};
+struct mjrRenderable {};
+struct mjrRenderTarget {};
+
+// Opaque type for the filament rendering context.
+struct mjrfContext {};
+
 typedef enum mjrGraphicsApi_ {  // backend graphics API to use
   mjGRAPHICS_API_DEFAULT = 0,   // default based on platform
   mjGRAPHICS_API_OPENGL,        // OpenGL (desktop) / WebGL