Introducing the download Framebuffer call on the context to capture a snapshot

interface/src/Application.cpp

@@ -2998,18 +2998,8 @@ PickRay Application::computePickRay(float x, float y) const {
 }
 
 QImage Application::renderAvatarBillboard(RenderArgs* renderArgs) {
-/*    auto primaryFramebuffer = DependencyManager::get<FramebufferCache>()->getPrimaryFramebuffer();
-    glBindFramebuffer(GL_FRAMEBUFFER, gpu::GLBackend::getFramebufferID(primaryFramebuffer));
 
-    // clear the alpha channel so the background is transparent
+    const int BILLBOARD_SIZE = 64;
-    glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE);
-    glClearColor(0.0, 0.0, 0.0, 0.0);
-    glClear(GL_COLOR_BUFFER_BIT);
-    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_FALSE);
-    */
-
- //   const int BILLBOARD_SIZE = 64;
-    const int BILLBOARD_SIZE = 256;
     _glWidget->makeCurrent();
 
     auto primaryFbo = DependencyManager::get<FramebufferCache>()->getPrimaryFramebuffer();
@@ -3020,26 +3010,18 @@ QImage Application::renderAvatarBillboard(RenderArgs* renderArgs) {
         batch.setFramebuffer(primaryFbo);
         renderArgs->_context->render(batch);
     }
-            renderArgs->_renderMode = RenderArgs::MIRROR_RENDER_MODE;
+    renderArgs->_renderMode = RenderArgs::NORMAL_RENDER_MODE;
-    renderRearViewMirror(renderArgs, QRect(0, /*_glWidget->getDeviceHeight() - BILLBOARD_SIZE*/ 0,
+    renderRearViewMirror(renderArgs, QRect(0, 0, BILLBOARD_SIZE, BILLBOARD_SIZE), true);
-                               BILLBOARD_SIZE, BILLBOARD_SIZE),
-                         false);
-        renderArgs->_renderMode = RenderArgs::NORMAL_RENDER_MODE;
 
-    auto selfieFbo = DependencyManager::get<FramebufferCache>()->getSelfieFramebuffer();
     {
         auto mirrorViewport = glm::ivec4(0, 0,BILLBOARD_SIZE, BILLBOARD_SIZE);
         gpu::Batch batch;
-       // batch.blit(primaryFbo, mirrorViewport, selfieFbo, mirrorViewport);
         batch.setFramebuffer(nullptr);
         renderArgs->_context->render(batch);
     }
     
-
     QImage image(BILLBOARD_SIZE, BILLBOARD_SIZE, QImage::Format_ARGB32);
-    glBindFramebuffer(GL_FRAMEBUFFER, gpu::GLBackend::getFramebufferID(primaryFbo));
+    renderArgs->_context->downloadFramebuffer(primaryFbo, glm::ivec4(0, 0, BILLBOARD_SIZE, BILLBOARD_SIZE), image);
-    glReadPixels(0, 0, BILLBOARD_SIZE, BILLBOARD_SIZE, GL_BGRA, GL_UNSIGNED_BYTE, image.bits());
-    glBindFramebuffer(GL_FRAMEBUFFER, 0);
 
     return image;
 }

libraries/gpu/src/gpu/Batch.h

@@ -108,7 +108,6 @@ public:
     void blit(const FramebufferPointer& src, const Vec4i& srcViewport,
         const FramebufferPointer& dst, const Vec4i& dstViewport);
 
-
     // Query Section
     void beginQuery(const QueryPointer& query);
     void endQuery(const QueryPointer& query);

libraries/gpu/src/gpu/Context.cpp

@@ -40,4 +40,8 @@ void Context::render(Batch& batch) {
 void Context::syncCache() {
     PROFILE_RANGE(__FUNCTION__);
     _backend->syncCache();
-}
+}
+
+void Context::downloadFramebuffer(const FramebufferPointer& srcFramebuffer, const Vec4i& region, QImage& destImage) {
+    _backend->downloadFramebuffer(srcFramebuffer, region, destImage);
+}

libraries/gpu/src/gpu/Context.h

@@ -28,6 +28,8 @@ public:
     virtual~ Backend() {};
     virtual void render(Batch& batch) = 0;
     virtual void syncCache() = 0;
+    virtual void downloadFramebuffer(const FramebufferPointer& srcFramebuffer, const Vec4i& region, QImage& destImage) = 0;
+
 
     class TransformObject {
     public:
@@ -121,6 +123,10 @@ public:
 
     void syncCache();
 
+    // Downloading the Framebuffer is a synchronous action that is not efficient.
+    // It s here for convenience to easily capture a snapshot
+    void downloadFramebuffer(const FramebufferPointer& srcFramebuffer, const Vec4i& region, QImage& destImage);
+
 protected:
     Context(const Context& context);
 

libraries/gpu/src/gpu/Framebuffer.h

@@ -14,8 +14,6 @@
 #include "Texture.h"
 #include <memory>
 
-class QImage;
-
 namespace gpu {
 
 typedef Element Format;

libraries/gpu/src/gpu/GLBackend.h

@@ -38,6 +38,10 @@ public:
     // Let's try to avoid to do that as much as possible!
     virtual void syncCache();
 
+    // This is the ugly "download the pixels to sysmem for taking a snapshot"
+    // Just avoid using it, it's ugly and will break performances
+    virtual void downloadFramebuffer(const FramebufferPointer& srcFramebuffer, const Vec4i& region, QImage& destImage);
+
     static bool checkGLError(const char* name = nullptr);
 
     // Only checks in debug builds

libraries/gpu/src/gpu/GLBackendOutput.cpp

@@ -11,6 +11,8 @@
 #include "GPULogging.h"
 #include "GLBackendShared.h"
 
+#include "qimage.h"
+
 using namespace gpu;
 
 GLBackend::GLFramebuffer::GLFramebuffer() {}
@@ -191,3 +193,13 @@ void GLBackend::do_blit(Batch& batch, uint32 paramOffset) {
         glBindFramebuffer(GL_DRAW_FRAMEBUFFER, getFramebufferID(_output._framebuffer));
     }
 }
+
+
+void GLBackend::downloadFramebuffer(const FramebufferPointer& srcFramebuffer, const Vec4i& region, QImage& destImage) {
+   
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, gpu::GLBackend::getFramebufferID(srcFramebuffer));
+    glReadPixels(region.x, region.y, region.z, region.w, GL_BGRA, GL_UNSIGNED_BYTE, destImage.bits());
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
+
+    (void) CHECK_GL_ERROR();
+}