Calculate and show Ambient shadow.
Basically we compute the shadow as a strip of triangles, whose alpha value
is the strength of the shadow.
We use the normal to extend the geometry.
And we use static function and try to avoid new/malloc in the computation.
Change-Id: I382286f1cad351bd5ff983f76f446c075819dcaf
diff --git a/libs/hwui/AmbientShadow.h b/libs/hwui/AmbientShadow.h
new file mode 100644
index 0000000..079bdb7
--- /dev/null
+++ b/libs/hwui/AmbientShadow.h
@@ -0,0 +1,57 @@
+
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_HWUI_AMBIENT_SHADOW_H
+#define ANDROID_HWUI_AMBIENT_SHADOW_H
+
+#include "Debug.h"
+#include "Vector.h"
+#include "VertexBuffer.h"
+
+namespace android {
+namespace uirenderer {
+
+/**
+ * AmbientShadow is used to calculate the ambient shadow value around a polygon.
+ *
+ * TODO: calculateIntersection() now is O(N*M), where N is the number of
+ * polygon's vertics and M is the number of rays. In fact, by staring tracing
+ * the vertex from the previous intersection, the algorithm can be O(N + M);
+ */
+class AmbientShadow {
+public:
+ static void createAmbientShadow(const Vector3* poly, int polyLength, int rays,
+ int layers, float strength, float heightFactor, float geomFactor,
+ VertexBuffer& shadowVertexBuffer);
+
+private:
+ static void calculatePolygonCentroid(const Vector3* poly, int len, Vector2& centroid);
+
+ static void calculateRayDirections(int rays, Vector2* dir);
+
+ static void calculateIntersection(const Vector3* poly, int nbVertices,
+ const Vector2& start, const Vector2& dir, int& outEdgeIndex,
+ float& outEdgeFraction, float& outRayDist);
+
+ static void calculateNormal(int rays, int currentRayIndex, const Vector2* dir,
+ const float* rayDist, Vector2& normal);
+}; // AmbientShadow
+
+}; // namespace uirenderer
+}; // namespace android
+
+#endif // ANDROID_HWUI_AMBIENT_SHADOW_H