1 
2 /*
3  * Copyright (C) 2013 The Android Open Source Project
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 
18 #ifndef ANDROID_HWUI_SHADOW_TESSELLATOR_H
19 #define ANDROID_HWUI_SHADOW_TESSELLATOR_H
20 
21 #include <SkPath.h>
22 
23 #include "Debug.h"
24 #include "Matrix.h"
25 
26 namespace android {
27 namespace uirenderer {
28 
29 class VertexBuffer;
30 
31 // All SHADOW_* are used to define all the geometry property of shadows.
32 // Use a simplified example to illustrate the geometry setup here.
33 // Assuming we use 6 rays and only 1 layer, Then we will have 2 hexagons, which
34 // are 0 to 5 and 6 to 11. The area between them will be the penumbra area, and
35 // the area inside the 2nd hexagon is the umbra.
36 // Ambient shadow is using only 1 layer for opaque caster, otherwise, spot
37 // shadow and ambient shadow are using 2 layers.
38 // Triange strip indices for penumbra area: (0, 6, 1, 7, 2, 8, 3, 9, 4, 10, 5, 11, 0, 6)
39 //                 0
40 //
41 //      5          6         1
42 //           11         7
43 //
44 //           10         8
45 //      4          9         2
46 //
47 //                 3
48 
49 // The total number of rays starting from the centroid of shadow area, in order
50 // to generate the shadow geometry.
51 #define SHADOW_RAY_COUNT 128
52 
53 // The total number of all the vertices representing the shadow.
54 // For the case we only have 1 layer, then we will just fill only 2/3 of it.
55 #define SHADOW_VERTEX_COUNT (3 * SHADOW_RAY_COUNT)
56 
57 // The total number of indices used for drawing the shadow geometry as triangle strips.
58 // Depending on the mode we are drawing, we can have 1 layer or 2 layers.
59 // Therefore, we only build the longer index buffer.
60 #define TWO_POLY_RING_SHADOW_INDEX_COUNT (4 * (SHADOW_RAY_COUNT + 1))
61 #define ONE_POLY_RING_SHADOW_INDEX_COUNT (2 * (SHADOW_RAY_COUNT + 1))
62 
63 #define MAX_SHADOW_INDEX_COUNT TWO_POLY_RING_SHADOW_INDEX_COUNT
64 
65 #define SHADOW_MIN_CASTER_Z 0.001f
66 
67 #define MINIMAL_DELTA_THETA (M_PI / 180 / 1000)
68 
69 class ShadowTessellator {
70 public:
71     static void tessellateAmbientShadow(bool isCasterOpaque,
72             const Vector3* casterPolygon, int casterVertexCount,
73             const Vector3& centroid3d,  const Rect& casterBounds,
74             const Rect& localClip, float maxZ, VertexBuffer& shadowVertexBuffer);
75 
76     static void tessellateSpotShadow(bool isCasterOpaque,
77             const Vector3* casterPolygon, int casterVertexCount, const Vector3& casterCentroid,
78             const mat4& receiverTransform, const Vector3& lightCenter, int lightRadius,
79             const Rect& casterBounds, const Rect& localClip, VertexBuffer& shadowVertexBuffer);
80 
81     static Vector2 centroid2d(const Vector2* poly, int polyLength);
82 
83     static bool isClockwise(const Vector2* polygon, int len);
84 
85     static Vector2 calculateNormal(const Vector2& p1, const Vector2& p2);
86 
87     static int getExtraVertexNumber(const Vector2& vector1, const Vector2& vector2,
88             float divisor);
89 
90     static void checkOverflow(int used, int total, const char* bufferName);
91 }; // ShadowTessellator
92 
93 }; // namespace uirenderer
94 }; // namespace android
95 
96 #endif // ANDROID_HWUI_SHADOW_TESSELLATOR_H
97