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/ShadowTessellator.cpp b/libs/hwui/ShadowTessellator.cpp
new file mode 100644
index 0000000..49a3d2c
--- /dev/null
+++ b/libs/hwui/ShadowTessellator.cpp
@@ -0,0 +1,73 @@
+/*
+ * 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.
+ */
+
+#define LOG_TAG "OpenGLRenderer"
+
+#include <math.h>
+#include <utils/Log.h>
+
+#include "AmbientShadow.h"
+#include "ShadowTessellator.h"
+
+namespace android {
+namespace uirenderer {
+
+// TODO: Support path as the input of the polygon instead of the rect's width
+// and height.
+void ShadowTessellator::tessellateAmbientShadow(float width, float height,
+ const mat4& casterTransform, VertexBuffer& shadowVertexBuffer) {
+
+ Vector3 pivot(width / 2, height / 2, 0.0f);
+ casterTransform.mapPoint3d(pivot);
+
+ // TODO: The zScaleFactor need to be mapped to the screen.
+ float zScaleFactor = 0.5;
+ Rect blockRect(pivot.x - width * zScaleFactor, pivot.y - height * zScaleFactor,
+ pivot.x + width * zScaleFactor, pivot.y + height * zScaleFactor);
+
+ // Generate the caster's polygon from the rect.
+ // TODO: support arbitrary polygon, and the z value need to be computed
+ // according to the transformation for each vertex.
+ const int vertexCount = 4;
+ Vector3 polygon[vertexCount];
+ polygon[0].x = blockRect.left;
+ polygon[0].y = blockRect.top;
+ polygon[0].z = pivot.z;
+ polygon[1].x = blockRect.right;
+ polygon[1].y = blockRect.top;
+ polygon[1].z = pivot.z;
+ polygon[2].x = blockRect.right;
+ polygon[2].y = blockRect.bottom;
+ polygon[2].z = pivot.z;
+ polygon[3].x = blockRect.left;
+ polygon[3].y = blockRect.bottom;
+ polygon[3].z = pivot.z;
+
+ // A bunch of parameters to tweak the shadow.
+ // TODO: Allow some of these changable by debug settings or APIs.
+ const int rays = 120;
+ const int layers = 2;
+ const float strength = 0.5;
+ const float heightFactor = 120;
+ const float geomFactor = 60;
+
+ AmbientShadow::createAmbientShadow(polygon, vertexCount, rays, layers, strength,
+ heightFactor, geomFactor, shadowVertexBuffer);
+
+}
+
+}; // namespace uirenderer
+}; // namespace android