GPv3: Render to Image

This PR refactors parts of the gpv3 engine and implements the `render_to_image` engine callback.

Pull Request: https://projects.blender.org/blender/blender/pulls/115904

source/blender/draw/engines/gpencil/gpencil_antialiasing.hh

@@ -44,7 +44,6 @@ class AntiAliasing {
   Framebuffer blend_weight_fb_ = {"blend_weight_fb"};
   PassSimple blend_weight_ps_ = {"blend_weight_ps"};
 
-  Framebuffer output_fb_ = {"output_fb"};
   PassSimple resolve_ps_ = {"resolve_ps"};
 
   bool draw_wireframe_ = false;
@@ -71,7 +70,7 @@ class AntiAliasing {
     anti_aliasing_enabled_ = true;  // GPENCIL_SIMPLIFY_AA(scene);
   }
 
-  void begin_sync(TextureFromPool &color_tx, TextureFromPool &reveal_tx)
+  void begin_sync(TextureFromPool &color_tx, Framebuffer &scene_fb, TextureFromPool &reveal_tx)
   {
     /* TODO(fclem): No global access. */
     const float *size = DRW_viewport_size_get();
@@ -83,7 +82,7 @@ class AntiAliasing {
     /* Resolve pass. */
     PassSimple &pass = resolve_ps_;
     pass.init();
-    pass.framebuffer_set(&output_fb_);
+    pass.framebuffer_set(&scene_fb);
     pass.state_set(DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_CUSTOM);
     pass.shader_set(shaders_.static_shader_get(ANTIALIASING_RESOLVE));
     /** \note use color_tx as dummy if AA is disabled. */
@@ -96,24 +95,21 @@ class AntiAliasing {
     pass.draw_procedural(GPU_PRIM_TRIS, 1, 3);
   }
 
-  void draw(Manager &manager, GPUTexture *dst_color_tx)
+  void draw(Manager &manager, const int2 render_resolution)
   {
-    int2 render_size = {GPU_texture_width(dst_color_tx), GPU_texture_height(dst_color_tx)};
-
     DRW_stats_group_start("Anti-Aliasing");
 
     if (anti_aliasing_enabled_) {
-      edge_detect_tx_.acquire(render_size, GPU_RG8);
+      edge_detect_tx_.acquire(render_resolution, GPU_RG8);
       edge_detect_fb_.ensure(GPU_ATTACHMENT_NONE, GPU_ATTACHMENT_TEXTURE(edge_detect_tx_));
       manager.submit(edge_detect_ps_);
 
-      blend_weight_tx_.acquire(render_size, GPU_RGBA8);
+      blend_weight_tx_.acquire(render_resolution, GPU_RGBA8);
       blend_weight_fb_.ensure(GPU_ATTACHMENT_NONE, GPU_ATTACHMENT_TEXTURE(blend_weight_tx_));
       manager.submit(blend_weight_ps_);
       edge_detect_tx_.release();
     }
 
-    output_fb_.ensure(GPU_ATTACHMENT_NONE, GPU_ATTACHMENT_TEXTURE(dst_color_tx));
     manager.submit(resolve_ps_);
     blend_weight_tx_.release();
 

source/blender/draw/engines/gpencil/gpencil_engine.cc

@@ -7,16 +7,25 @@
  */
 
 #include "BKE_gpencil_modifier_legacy.h"
+
 #include "BLI_listbase_wrapper.hh"
+
 #include "DEG_depsgraph_query.hh"
+
 #include "DNA_shader_fx_types.h"
+
 #include "DRW_engine.h"
 #include "DRW_render.h"
+
 #include "ED_screen.hh"
 #include "ED_view3d.hh"
+
 #include "GPU_capabilities.h"
+
 #include "IMB_imbuf_types.h"
 
+#include "RE_pipeline.h"
+
 #include "draw_manager.hh"
 #include "draw_pass.hh"
 
@@ -55,6 +64,10 @@ class Instance {
   TextureFromPool reveal_tx_ = {"gp_reveal_tx"};
   Framebuffer main_fb_ = {"gp_main_fb"};
 
+  /** Underlying scene pixel. Used to composite the output of the grease pencil render onto the
+   * scene (including merging the depth buffers). */
+  Framebuffer scene_fb_ = {"gp_scene_fb"};
+
   /** Texture format for all intermediate buffers. */
   eGPUTextureFormat texture_format_ = GPU_RGBA16F;
 
@@ -76,6 +89,8 @@ class Instance {
   /** Context. */
   Depsgraph *depsgraph_ = nullptr;
   Object *camera_ = nullptr;
+  Manager *manager_ = nullptr;
+  draw::View view_ = {"MainView"};
 
   /** \note Needs not to be temporary variable since it is dereferenced later. */
   std::array<float4, 2> clear_colors_ = {float4(0.0f, 0.0f, 0.0f, 0.0f),
@@ -88,9 +103,18 @@ class Instance {
         vfx(shaders),
         anti_aliasing(shaders){};
 
-  void init(Depsgraph *depsgraph, const View3D *v3d, const RegionView3D *rv3d)
+  void init(Depsgraph *depsgraph,
+            Manager *manager,
+            const DRWView *viewport_draw_view,
+            const View3D *v3d,
+            const RegionView3D *rv3d)
   {
     depsgraph_ = depsgraph;
+    manager_ = manager;
+    if (viewport_draw_view != nullptr) {
+      view_.sync(viewport_draw_view);
+    }
+
     const Scene *scene = DEG_get_evaluated_scene(depsgraph_);
 
     const bool is_viewport = (v3d != nullptr);
@@ -108,12 +132,9 @@ class Instance {
     anti_aliasing.init(v3d, scene);
   }
 
-  void begin_sync(Manager & /*manager*/)
+  void begin_sync()
   {
-    /* TODO(fclem): Remove global draw manager access. */
-    View main_view("GPencil_MainView", DRW_view_default_get());
-
-    objects.begin_sync(depsgraph_, main_view);
+    objects.begin_sync(depsgraph_, view_);
     layers.begin_sync();
     materials.begin_sync();
     lights.begin_sync(depsgraph_);
@@ -133,14 +154,15 @@ class Instance {
     materials.bind_resources(sub);
     lights.bind_resources(sub);
 
-    anti_aliasing.begin_sync(color_tx_, reveal_tx_);
+    anti_aliasing.begin_sync(color_tx_, scene_fb_, reveal_tx_);
   }
 
-  void object_sync(Manager &manager, ObjectRef &object_ref)
+  void object_sync(ObjectRef &object_ref)
   {
     switch (object_ref.object->type) {
       case OB_GREASE_PENCIL:
-        objects.sync_grease_pencil(manager, object_ref, main_fb_, depth_tx_, main_ps_);
+        objects.sync_grease_pencil(
+            *manager_, object_ref, main_fb_, scene_fb_, depth_tx_, main_ps_);
         break;
       case OB_LAMP:
         lights.sync(object_ref);
@@ -150,7 +172,7 @@ class Instance {
     }
   }
 
-  void end_sync(Manager & /*manager*/)
+  void end_sync()
   {
     objects.end_sync();
     layers.end_sync();
@@ -158,39 +180,68 @@ class Instance {
     lights.end_sync();
   }
 
-  void draw_viewport(Manager &manager,
-                     View &view,
-                     GPUTexture *dst_depth_tx,
-                     GPUTexture *dst_color_tx)
+  void render_sync(RenderEngine *engine, Depsgraph *depsgraph)
+  {
+    /* TODO: Remove old draw manager calls. */
+    DRW_cache_restart();
+
+    manager_->begin_sync();
+
+    begin_sync();
+
+    auto object_sync_render =
+        [](void *vedata, Object *ob, RenderEngine * /*engine*/, Depsgraph * /*depsgraph*/) {
+          Instance &inst = *reinterpret_cast<Instance *>(vedata);
+          ObjectRef ob_ref = DRW_object_ref_get(ob);
+          inst.object_sync(ob_ref);
+        };
+
+    /* HACK: We pass `this` here so we have access to the `Instance` in `object_sync_render`. */
+    DRW_render_object_iter(this, engine, depsgraph, object_sync_render);
+
+    end_sync();
+
+    manager_->end_sync();
+
+    /* TODO: Remove old draw manager calls. */
+    DRW_render_instance_buffer_finish();
+  }
+
+  void draw(GPUTexture *dst_color_tx, GPUTexture *dst_depth_tx, const int2 render_resolution)
   {
     if (!objects.scene_has_visible_gpencil_object()) {
       return;
     }
 
-    int2 render_size = {GPU_texture_width(dst_depth_tx), GPU_texture_height(dst_depth_tx)};
+    scene_fb_.ensure(GPU_ATTACHMENT_TEXTURE(dst_depth_tx), GPU_ATTACHMENT_TEXTURE(dst_color_tx));
 
-    depth_tx_.acquire(render_size, GPU_DEPTH24_STENCIL8);
-    color_tx_.acquire(render_size, texture_format_);
-    reveal_tx_.acquire(render_size, texture_format_);
+    depth_tx_.acquire(render_resolution, GPU_DEPTH24_STENCIL8);
+    color_tx_.acquire(render_resolution, texture_format_);
+    reveal_tx_.acquire(render_resolution, texture_format_);
     main_fb_.ensure(GPU_ATTACHMENT_TEXTURE(depth_tx_),
                     GPU_ATTACHMENT_TEXTURE(color_tx_),
                     GPU_ATTACHMENT_TEXTURE(reveal_tx_));
 
-    scene_buf_.render_size = float2(render_size);
+    scene_buf_.render_size = float2(render_resolution);
     scene_buf_.push_update();
 
-    objects.acquire_temporary_buffers(render_size, texture_format_);
+    objects.acquire_temporary_buffers(render_resolution, texture_format_);
 
-    manager.submit(main_ps_, view);
+    manager_->submit(main_ps_, view_);
 
     objects.release_temporary_buffers();
 
-    anti_aliasing.draw(manager, dst_color_tx);
+    anti_aliasing.draw(*manager_, render_resolution);
 
     depth_tx_.release();
     color_tx_.release();
     reveal_tx_.release();
   }
+
+  draw::View &view()
+  {
+    return view_;
+  }
 };
 
 }  // namespace blender::draw::greasepencil
@@ -219,9 +270,12 @@ static void gpencil_engine_init(void *vedata)
     ved->instance = new draw::greasepencil::Instance();
   }
 
+  draw::Manager *manager = DRW_manager_get();
   const DRWContextState *ctx_state = DRW_context_state_get();
+  const DRWView *default_view = DRW_view_default_get();
 
-  ved->instance->init(ctx_state->depsgraph, ctx_state->v3d, ctx_state->rv3d);
+  ved->instance->init(
+      ctx_state->depsgraph, manager, default_view, ctx_state->v3d, ctx_state->rv3d);
 }
 
 static void gpencil_draw_scene(void *vedata)
@@ -232,33 +286,29 @@ static void gpencil_draw_scene(void *vedata)
   }
   DefaultTextureList *dtxl = DRW_viewport_texture_list_get();
   const DRWView *default_view = DRW_view_default_get();
-  draw::Manager *manager = DRW_manager_get();
-  draw::View view("DefaultView", default_view);
-  ved->instance->draw_viewport(*manager, view, dtxl->depth, dtxl->color);
+  const float2 viewport_size = DRW_viewport_size_get();
+  ved->instance->view().sync(default_view);
+  ved->instance->draw(dtxl->color, dtxl->depth, int2(viewport_size));
 }
 
 static void gpencil_cache_init(void *vedata)
 {
-  draw::Manager *manager = DRW_manager_get();
-  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->begin_sync(*manager);
+  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->begin_sync();
 }
 
 static void gpencil_cache_populate(void *vedata, Object *object)
 {
-  draw::Manager *manager = DRW_manager_get();
-
   draw::ObjectRef ref;
   ref.object = object;
   ref.dupli_object = DRW_object_get_dupli(object);
   ref.dupli_parent = DRW_object_get_dupli_parent(object);
 
-  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->object_sync(*manager, ref);
+  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->object_sync(ref);
 }
 
 static void gpencil_cache_finish(void *vedata)
 {
-  draw::Manager *manager = DRW_manager_get();
-  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->end_sync(*manager);
+  reinterpret_cast<GPENCIL_NEXT_Data *>(vedata)->instance->end_sync();
 }
 
 static void gpencil_instance_free(void *instance)
@@ -271,11 +321,107 @@ static void gpencil_engine_free()
   blender::draw::greasepencil::ShaderModule::module_free();
 }
 
+/** Get the color and depth textures of the render result in the render layer. */
+static void get_render_result_textures(RenderEngine *engine,
+                                       RenderLayer *render_layer,
+                                       const draw::View &view,
+                                       const int2 render_resolution,
+                                       draw::Texture &r_color_tx,
+                                       draw::Texture &r_depth_tx)
+{
+  /* Create depth texture & color texture from render result. */
+  const char *viewname = RE_GetActiveRenderView(engine->re);
+  RenderPass *rpass_z_src = RE_pass_find_by_name(render_layer, RE_PASSNAME_Z, viewname);
+  RenderPass *rpass_col_src = RE_pass_find_by_name(render_layer, RE_PASSNAME_COMBINED, viewname);
+
+  float *pix_z = (rpass_z_src) ? rpass_z_src->ibuf->float_buffer.data : nullptr;
+  float *pix_col = (rpass_col_src) ? rpass_col_src->ibuf->float_buffer.data : nullptr;
+
+  if (!pix_z || !pix_col) {
+    RE_engine_set_error_message(engine,
+                                "Warning: To render grease pencil, enable Combined and Z passes.");
+  }
+
+  if (pix_z) {
+    /* Depth need to be remapped to [0..1] range. */
+    pix_z = static_cast<float *>(MEM_dupallocN(pix_z));
+
+    int pix_num = rpass_z_src->rectx * rpass_z_src->recty;
+
+    if (view.is_persp()) {
+      for (int i = 0; i < pix_num; i++) {
+        pix_z[i] = (-view.winmat()[3][2] / -pix_z[i]) - view.winmat()[2][2];
+        pix_z[i] = clamp_f(pix_z[i] * 0.5f + 0.5f, 0.0f, 1.0f);
+      }
+    }
+    else {
+      /* Keep in mind, near and far distance are negatives. */
+      float near = view.near_clip();
+      float far = view.far_clip();
+      float range_inv = 1.0f / fabsf(far - near);
+      for (int i = 0; i < pix_num; i++) {
+        pix_z[i] = (pix_z[i] + near) * range_inv;
+        pix_z[i] = clamp_f(pix_z[i], 0.0f, 1.0f);
+      }
+    }
+  }
+
+  /* FIXME(fclem): we have a precision loss in the depth buffer because of this re-upload.
+   * Find where it comes from! */
+  const eGPUTextureUsage usage = GPU_TEXTURE_USAGE_ATTACHMENT | GPU_TEXTURE_USAGE_HOST_READ;
+  r_depth_tx.ensure_2d(GPU_DEPTH_COMPONENT24, render_resolution, usage, pix_z);
+  r_color_tx.ensure_2d(GPU_RGBA16F, render_resolution, usage, pix_col);
+}
+
 static void gpencil_render_to_image(void * /*vedata*/,
-                                    RenderEngine * /*engine*/,
-                                    RenderLayer * /*layer*/,
+                                    RenderEngine *engine,
+                                    RenderLayer *render_layer,
                                     const rcti * /*rect*/)
 {
+  draw::greasepencil::Instance instance;
+  draw::Manager &manager = *DRW_manager_get();
+
+  Render *render = engine->re;
+  Depsgraph *depsgraph = DRW_context_state_get()->depsgraph;
+  Scene *scene = DRW_context_state_get()->scene;
+  Object *camera_original_ob = RE_GetCamera(render);
+  const char *viewname = RE_GetActiveRenderView(render);
+  const int2 render_resolution = int2(engine->resolution_x, engine->resolution_y);
+
+  instance.init(depsgraph, &manager, nullptr, nullptr, nullptr);
+
+  float4x4 viewinv, winmat;
+  Object *camera_eval = DEG_get_evaluated_object(depsgraph, camera_original_ob);
+  RE_GetCameraModelMatrix(render, camera_eval, viewinv.ptr());
+  float4x4 viewmat = math::invert(viewinv);
+  RE_GetCameraWindow(render, camera_eval, winmat.ptr());
+
+  instance.view().sync(viewmat, winmat);
+  instance.render_sync(engine, depsgraph);
+
+  draw::Texture color_tx;
+  draw::Texture depth_tx;
+  /* TODO: Support `R_BORDER` render mode. */
+  get_render_result_textures(
+      engine, render_layer, instance.view(), render_resolution, color_tx, depth_tx);
+
+  instance.draw(color_tx, depth_tx, render_resolution);
+
+  RenderPass *rp = RE_pass_find_by_name(render_layer, RE_PASSNAME_COMBINED, viewname);
+  if (!rp) {
+    return;
+  }
+  float *result = reinterpret_cast<float *>(color_tx.read<float4>(GPU_DATA_FLOAT));
+
+  if (result) {
+    BLI_mutex_lock(&engine->update_render_passes_mutex);
+    /* WORKAROUND: We use texture read to avoid using a frame-buffer to get the render result.
+     * However, on some implementation, we need a buffer with a few extra bytes for the read to
+     * happen correctly (see #GLTexture::read()). So we need a custom memory allocation. */
+    /* Avoid `memcpy()`, replace the pointer directly. */
+    RE_pass_set_buffer_data(rp, result);
+    BLI_mutex_unlock(&engine->update_render_passes_mutex);
+  }
 }
 
 extern "C" {

source/blender/draw/engines/gpencil/gpencil_object.hh

@@ -110,6 +110,7 @@ class ObjectModule {
   void sync_grease_pencil(Manager &manager,
                           ObjectRef &object_ref,
                           Framebuffer &main_fb,
+                          Framebuffer &scene_fb,
                           TextureFromPool &depth_tx,
                           PassSortable &main_ps)
   {
@@ -196,9 +197,10 @@ class ObjectModule {
       object_subpass.draw(geom, handle);
     }
 
+    /** Merging the object depth buffer into the scene depth buffer. */
     float4x4 plane_mat = get_object_plane_mat(*object);
     ResourceHandle handle_plane_mat = manager.resource_handle(plane_mat);
-    object_subpass.framebuffer_set(&DRW_viewport_framebuffer_list_get()->depth_only_fb);
+    object_subpass.framebuffer_set(&scene_fb);
     object_subpass.state_set(DRW_STATE_DEPTH_LESS | DRW_STATE_WRITE_DEPTH);
     object_subpass.shader_set(shaders_.static_shader_get(DEPTH_MERGE));
     object_subpass.bind_texture("depthBuf", (object_has_vfx) ? nullptr : &depth_tx);