cleanup model fade logic

interface/src/avatar/CauterizedModel.cpp

@@ -225,9 +225,6 @@ void CauterizedModel::updateRenderItems() {
             foreach (auto itemID, keys) {
                 pendingChanges.updateItem<CauterizedMeshPartPayload>(itemID, [modelTransform, deleteGeometryCounter](CauterizedMeshPartPayload& data) {
                     if (data._model && data._model->isLoaded()) {
-                        if (!data.hasStartedFade() && data._model->getGeometry()->areTexturesLoaded()) {
-                            data.startFade();
-                        }
                         // Ensure the model geometry was not reset between frames
                         if (deleteGeometryCounter == data._model->getGeometryCounter()) {
                             // lazy update of cluster matrices used for rendering.  We need to update them here, so we can correctly update the bounding box.

libraries/render-utils/src/MeshPartPayload.cpp

@@ -402,7 +402,7 @@ ItemKey ModelMeshPartPayload::getKey() const {
         }
     }
 
-    if (!_hasFinishedFade) {
+    if (_fadeState != FADE_COMPLETE) {
         builder.withTransparent();
     }
 
@@ -472,7 +472,7 @@ ShapeKey ModelMeshPartPayload::getShapeKey() const {
     }
 
     ShapeKey::Builder builder;
-    if (isTranslucent || !_hasFinishedFade) {
+    if (isTranslucent || _fadeState != FADE_COMPLETE) {
         builder.withTranslucent();
     }
     if (hasTangents) {
@@ -513,9 +513,10 @@ void ModelMeshPartPayload::bindMesh(gpu::Batch& batch) const {
         batch.setInputStream(2, _drawMesh->getVertexStream().makeRangedStream(2));
     }
 
-    float fadeRatio = _isFading ? Interpolate::calculateFadeRatio(_fadeStartTime) : 1.0f;
+    if (_fadeState != FADE_COMPLETE) {
-    if (!_hasColorAttrib || fadeRatio < 1.0f) {
+        batch._glColor4f(1.0f, 1.0f, 1.0f, computeFadeAlpha());
-        batch._glColor4f(1.0f, 1.0f, 1.0f, fadeRatio);
+    } else if (!_hasColorAttrib) {
+        batch._glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
     }
 }
 
@@ -528,17 +529,23 @@ void ModelMeshPartPayload::bindTransform(gpu::Batch& batch, const ShapePipeline:
     batch.setModelTransform(_transform);
 }
 
-void ModelMeshPartPayload::startFade() {
+float ModelMeshPartPayload::computeFadeAlpha() const {
-    bool shouldFade = EntityItem::getEntitiesShouldFadeFunction()();
+    if (_fadeState == FADE_WAITING_TO_START) {
-    if (shouldFade) {
+        return 0.0f;
-        _fadeStartTime = usecTimestampNow();
-        _hasStartedFade = true;
-        _hasFinishedFade = false;
-    } else {
-        _isFading = true;
-        _hasStartedFade = true;
-        _hasFinishedFade = true;
     }
+    float fadeAlpha = 1.0f;
+    const float INV_FADE_PERIOD = 1.0f / (float)(1 * USECS_PER_SECOND);
+    float fraction = (float)(usecTimestampNow() - _fadeStartTime) * INV_FADE_PERIOD;
+    if (fraction < 1.0f) {
+        fadeAlpha = Interpolate::simpleNonLinearBlend(fraction);
+    }
+    if (fadeAlpha >= 1.0f) {
+        _fadeState = FADE_COMPLETE;
+        // when fade-in completes we flag model for one last "render item update"
+        _model->setRenderItemsNeedUpdate();
+        return 1.0f;
+    }
+    return Interpolate::simpleNonLinearBlend(fadeAlpha);
 }
 
 void ModelMeshPartPayload::render(RenderArgs* args) const {
@@ -548,33 +555,28 @@ void ModelMeshPartPayload::render(RenderArgs* args) const {
         return; // bail asap
     }
 
-    // If we didn't start the fade in, check if we are ready to now....
+    if (_fadeState == FADE_WAITING_TO_START) {
-    if (!_hasStartedFade && _model->isLoaded() && _model->getGeometry()->areTexturesLoaded()) {
+        if (_model->isLoaded() && _model->getGeometry()->areTexturesLoaded()) {
-        const_cast<ModelMeshPartPayload&>(*this).startFade();
+            if (EntityItem::getEntitiesShouldFadeFunction()()) {
+                _fadeStartTime = usecTimestampNow();
+                _fadeState = FADE_IN_PROGRESS;
+            } else {
+                _fadeState = FADE_COMPLETE;
             }
-
+            _model->setRenderItemsNeedUpdate();
-    // If we still didn't start the fade in, bail
+        } else {
-    if (!_hasStartedFade) {
             return;
         }
-
-    // When an individual mesh parts like this finishes its fade, we will mark the Model as
-    // having render items that need updating
-    bool nextIsFading = _isFading ? isStillFading() : false;
-    bool startFading = !_isFading && !_hasFinishedFade && _hasStartedFade;
-    bool endFading = _isFading && !nextIsFading;
-    if (startFading || endFading) {
-        _isFading = startFading;
-        _hasFinishedFade = endFading;
-        _model->setRenderItemsNeedUpdate();
     }
 
-    gpu::Batch& batch = *(args->_batch);
+    if (!args) {
-
+        return;
+    }
     if (!getShapeKey().isValid()) {
         return;
     }
 
+    gpu::Batch& batch = *(args->_batch);
     auto locations =  args->_pipeline->locations;
     assert(locations);
 
@@ -588,9 +590,7 @@ void ModelMeshPartPayload::render(RenderArgs* args) const {
     // apply material properties
     bindMaterial(batch, locations);
 
-    if (args) {
     args->_details._materialSwitches++;
-    }
 
     // Draw!
     {
@@ -598,8 +598,6 @@ void ModelMeshPartPayload::render(RenderArgs* args) const {
         drawCall(batch);
     }
 
-    if (args) {
     const int INDICES_PER_TRIANGLE = 3;
     args->_details._trianglesRendered += _drawPart._numIndices / INDICES_PER_TRIANGLE;
-    }
 }

libraries/render-utils/src/MeshPartPayload.h

@@ -21,6 +21,10 @@
 
 #include <model/Geometry.h>
 
+const uint8_t FADE_WAITING_TO_START = 0;
+const uint8_t FADE_IN_PROGRESS = 1;
+const uint8_t FADE_COMPLETE = 2;
+
 class Model;
 
 class MeshPartPayload {
@@ -87,10 +91,7 @@ public:
     void updateTransformForSkinnedMesh(const Transform& transform,
             const QVector<glm::mat4>& clusterMatrices);
 
-    // Entity fade in
+    float computeFadeAlpha() const;
-    void startFade();
-    bool hasStartedFade() { return _hasStartedFade; }
-    bool isStillFading() const { return Interpolate::calculateFadeRatio(_fadeStartTime) < 1.0f; }
 
     // Render Item interface
     render::ItemKey getKey() const override;
@@ -113,10 +114,8 @@ public:
     bool _isBlendShaped{ false };
 
 private:
-    quint64 _fadeStartTime { 0 };
+    mutable quint64 _fadeStartTime { 0 };
-    bool _hasStartedFade { false };
+    mutable uint8_t _fadeState { FADE_WAITING_TO_START };
-    mutable bool _hasFinishedFade { false };
-    mutable bool _isFading { false };
 };
 
 namespace render {

libraries/render-utils/src/Model.cpp

@@ -227,9 +227,6 @@ void Model::updateRenderItems() {
         foreach (auto itemID, self->_modelMeshRenderItems.keys()) {
             pendingChanges.updateItem<ModelMeshPartPayload>(itemID, [modelTransform, deleteGeometryCounter](ModelMeshPartPayload& data) {
                 if (data._model && data._model->isLoaded()) {
-                    if (!data.hasStartedFade() && data._model->getGeometry()->areTexturesLoaded()) {
-                        data.startFade();
-                    }
                     // Ensure the model geometry was not reset between frames
                     if (deleteGeometryCounter == data._model->_deleteGeometryCounter) {
                         // lazy update of cluster matrices used for rendering.  We need to update them here, so we can correctly update the bounding box.
@@ -1450,7 +1447,6 @@ void ModelBlender::noteRequiresBlend(ModelPointer model) {
 
     {
         Lock lock(_mutex);
-
         _modelsRequiringBlends.insert(model);
     }
 }

libraries/shared/src/Interpolate.cpp

@@ -61,6 +61,13 @@ float Interpolate::interpolate3Points(float y1, float y2, float y3, float u) {
     }
 }
 
+float Interpolate::simpleNonLinearBlend(float fraction) {
+    // uses arctan() to map a linear distribution in domain [0,1] to a non-linear blend (slow out, slow in) in range [0,1]
+    const float WIDTH = 20.0f;
+    const float INV_ARCTAN_WIDTH = 0.339875327433f; // 1 / (2 * atan(WIDTH/2))
+    return 0.5f + atanf(WIDTH * (fraction - 0.5f)) * INV_ARCTAN_WIDTH;
+}
+
 float Interpolate::calculateFadeRatio(quint64 start) {
     const float FADE_TIME = 1.0f;
     float t = 2.0f * std::min(((float)(usecTimestampNow() - start)) / ((float)(FADE_TIME * USECS_PER_SECOND)), 1.0f);

libraries/shared/src/Interpolate.h

@@ -25,6 +25,10 @@ public:
     // pass through all three y values. Return value lies wholly within the range of y values passed in.
     static float interpolate3Points(float y1, float y2, float y3, float u);
 
+    // returns smooth in and out blend between 0 and 1
+    // DANGER: assumes fraction is properly inside range [0, 1]
+    static float simpleNonLinearBlend(float fraction);
+
     static float calculateFadeRatio(quint64 start);
 };