Reduce stereoscopic texture sizes when unused

Initially and when left & right eye textures are not used,
minimize their size.

Task-number: QT3DS-3084
Change-Id: Id6b5252cb1a9bc8b9bca64696268b71353a95ca4
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

2 files changed, 34 insertions, 16 deletions

diff --git a/src/runtime/q3dsscenemanager.cpp b/src/runtime/q3dsscenemanager.cpp
index 0b307b9..4cabab1 100644
--- a/src/runtime/q3dsscenemanager.cpp
+++ b/src/runtime/q3dsscenemanager.cpp
@@ -1368,6 +1368,7 @@ void Q3DSSceneManager::buildLayer(Q3DSLayerNode *layer3DS,
     // parentSize could well be (0, 0) at this stage still, nevermind that
     const QSize layerSize = calculateLayerSize(layer3DS, parentSize);
     const QSize layerPixelSize = safeLayerPixelSize(layerSize, ssaaScaleFactor);
+    const QSize dummyLayerSize = QSize(1,1);
 
     Q3DSLayerAttached *layerData = new Q3DSLayerAttached;
     ViewportSet viewports;
@@ -1386,9 +1387,12 @@ void Q3DSSceneManager::buildLayer(Q3DSLayerNode *layer3DS,
 
     // Create color and depth-stencil buffers for this layer
     // Stereoscopic left-eye
-    Qt3DRender::QAbstractTexture *colorTexLeft;
-    Qt3DRender::QAbstractTexture *dsTexOrRbLeft;
-    Qt3DRender::QRenderTarget *rtLeft = newLayerRenderTarget(layerPixelSize, msaaSampleCount, &colorTexLeft, &dsTexOrRbLeft, layerFgRoot, layer3DS);
+    Q3DSLayerAttached::SizeManagedTexture colorTexLeft;
+    Q3DSLayerAttached::SizeManagedTexture dsTexOrRbLeft;
+    // Mark textures being for stereoscopic usage
+    colorTexLeft.flags |= Q3DSLayerAttached::SizeManagedTexture::StereoscopicView;
+    dsTexOrRbLeft.flags |= Q3DSLayerAttached::SizeManagedTexture::StereoscopicView;
+    Qt3DRender::QRenderTarget *rtLeft = newLayerRenderTarget(dummyLayerSize, msaaSampleCount, &colorTexLeft.texture, &dsTexOrRbLeft.texture, layerFgRoot, layer3DS);
     m_profiler->trackNewObject(rtLeft, Q3DSProfiler::RenderTargetObject,
                                "RT for layer %s", layer3DS->id().constData());
     rtSelectorLeft->setTarget(rtLeft);
@@ -1398,9 +1402,12 @@ void Q3DSSceneManager::buildLayer(Q3DSLayerNode *layer3DS,
 
     // Create color and depth-stencil buffers for this layer
     // Stereoscopic right-eye
-    Qt3DRender::QAbstractTexture *colorTexRight;
-    Qt3DRender::QAbstractTexture *dsTexOrRbRight;
-    Qt3DRender::QRenderTarget *rtRight = newLayerRenderTarget(layerPixelSize, msaaSampleCount, &colorTexRight, &dsTexOrRbRight, layerFgRoot, layer3DS);
+    Q3DSLayerAttached::SizeManagedTexture colorTexRight;
+    Q3DSLayerAttached::SizeManagedTexture dsTexOrRbRight;
+    // Mark textures being for stereoscopic usage
+    colorTexRight.flags |= Q3DSLayerAttached::SizeManagedTexture::StereoscopicView;
+    dsTexOrRbRight.flags |= Q3DSLayerAttached::SizeManagedTexture::StereoscopicView;
+    Qt3DRender::QRenderTarget *rtRight = newLayerRenderTarget(dummyLayerSize, msaaSampleCount, &colorTexRight.texture, &dsTexOrRbRight.texture, layerFgRoot, layer3DS);
     m_profiler->trackNewObject(rtRight, Q3DSProfiler::RenderTargetObject,
                                "RT for layer %s", layer3DS->id().constData());
     rtSelectorRight->setTarget(rtRight);
@@ -1442,10 +1449,10 @@ void Q3DSSceneManager::buildLayer(Q3DSLayerNode *layer3DS,
     layerData->sizeManagedTextures << colorTex << dsTexOrRb;
 
     // Setup for stereo left / eye
-    layerData->eyeLeft->layerTexture = colorTexLeft;
-    layerData->eyeRight->layerTexture = colorTexRight;
-    layerData->eyeLeft->layerDS = dsTexOrRbLeft;
-    layerData->eyeRight->layerDS = dsTexOrRbRight;
+    layerData->eyeLeft->layerTexture = colorTexLeft.texture;
+    layerData->eyeRight->layerTexture = colorTexRight.texture;
+    layerData->eyeLeft->layerDS = dsTexOrRbLeft.texture;
+    layerData->eyeRight->layerDS = dsTexOrRbRight.texture;
     layerData->eyeLeft->compositorSourceParam = new Qt3DRender::QParameter(QLatin1String("texLeft"), layerData->eyeLeft->layerTexture);
     layerData->eyeRight->compositorSourceParam = new Qt3DRender::QParameter(QLatin1String("texRight"), layerData->eyeRight->layerTexture);
     layerData->eyeLeft->rtSelector = rtSelectorLeft;
@@ -2055,13 +2062,23 @@ void Q3DSSceneManager::setLayerSizeProperties(Q3DSLayerNode *layer3DS)
     const QSize layerSize = safeLayerPixelSize(data->layerSize, 1); // for when SSAA is to be ignored
     for (const Q3DSLayerAttached::SizeManagedTexture &t : data->sizeManagedTextures) {
         if (!t.flags.testFlag(Q3DSLayerAttached::SizeManagedTexture::CustomSizeCalculation)) {
+            int w = layerSize.width();
+            int h = layerSize.height();
             if (!t.flags.testFlag(Q3DSLayerAttached::SizeManagedTexture::IgnoreSSAA)) {
-                t.texture->setWidth(layerPixelSize.width());
-                t.texture->setHeight(layerPixelSize.height());
-            } else {
-                t.texture->setWidth(layerSize.width());
-                t.texture->setHeight(layerSize.height());
+                w = layerPixelSize.width();
+                h = layerPixelSize.height();
+            }
+            if (t.flags.testFlag(Q3DSLayerAttached::SizeManagedTexture::StereoscopicView)
+                                 && !m_engine->isStereoscopic()) {
+                // When not in stereoscopic mode, reduce left & right eye texture sizes to
+                // not consume memory. Once user switches to stereoscopic, they will be resized
+                // automatically to full size again.
+                w = 1;
+                h = 1;
+
             }
+            t.texture->setWidth(w);
+            t.texture->setHeight(h);
         }
         if (t.sizeChangeCallback)
             t.sizeChangeCallback(layer3DS);
diff --git a/src/runtime/q3dsscenemanager_p.h b/src/runtime/q3dsscenemanager_p.h
index 5cdb806..cc0cbaf 100644
--- a/src/runtime/q3dsscenemanager_p.h
+++ b/src/runtime/q3dsscenemanager_p.h
@@ -304,7 +304,8 @@ public:
     struct SizeManagedTexture {
         enum Flag {
             IgnoreSSAA = 0x01,
-            CustomSizeCalculation = 0x02
+            CustomSizeCalculation = 0x02,
+            StereoscopicView = 0x04
         };
         Q_DECLARE_FLAGS(Flags, Flag)
         SizeManagedTexture() { }