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 "Debug.h"
22#include "Matrix.h"
23#include "OpenGLRenderer.h"
24#include "VertexBuffer.h"
25
26namespace android {
27namespace uirenderer {
28
29// All SHADOW_* are used to define all the geometry property of shadows.
30// Use a simplified example to illustrate the geometry setup here.
31// Assuming we use 6 rays and only 1 layer, Then we will have 2 hexagons, which
32// are 0 to 5 and 6 to 11. The area between them will be the penumbra area, and
33// the area inside the 2nd hexagon is the umbra.
34// Ambient shadow is using only 1 layer for opaque caster, otherwise, spot
35// shadow and ambient shadow are using 2 layers.
36// Triange strip indices for penumbra area: (0, 6, 1, 7, 2, 8, 3, 9, 4, 10, 5, 11, 0, 6)
37//                 0
38//
39//      5          6         1
40//           11         7
41//
42//           10         8
43//      4          9         2
44//
45//                 3
46
47// The total number of rays starting from the centroid of shadow area, in order
48// to generate the shadow geometry.
49#define SHADOW_RAY_COUNT 128
50
51// The total number of all the vertices representing the shadow.
52// For the case we only have 1 layer, then we will just fill only 2/3 of it.
53#define SHADOW_VERTEX_COUNT (3 * SHADOW_RAY_COUNT)
54
55// The total number of indices used for drawing the shadow geometry as triangle strips.
56// Depending on the mode we are drawing, we can have 1 layer or 2 layers.
57// Therefore, we only build the longer index buffer.
58#define TWO_POLY_RING_SHADOW_INDEX_COUNT (4 * (SHADOW_RAY_COUNT + 1))
59#define ONE_POLY_RING_SHADOW_INDEX_COUNT (2 * (SHADOW_RAY_COUNT + 1))
60
61#define MAX_SHADOW_INDEX_COUNT TWO_POLY_RING_SHADOW_INDEX_COUNT
62
63#define SHADOW_MIN_CASTER_Z 0.001f
64
65#define MINIMAL_DELTA_THETA (M_PI / 180 / 1000)
66
67class ShadowTessellator {
68public:
69    static void tessellateAmbientShadow(bool isCasterOpaque,
70            const Vector3* casterPolygon, int casterVertexCount,
71            const Vector3& centroid3d,  const Rect& casterBounds,
72            const Rect& localClip, float maxZ, VertexBuffer& shadowVertexBuffer);
73
74    static void tessellateSpotShadow(bool isCasterOpaque,
75            const Vector3* casterPolygon, int casterVertexCount, const Vector3& casterCentroid,
76            const mat4& receiverTransform, const Vector3& lightCenter, int lightRadius,
77            const Rect& casterBounds, const Rect& localClip, VertexBuffer& shadowVertexBuffer);
78
79    static void generateShadowIndices(uint16_t*  shadowIndices);
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     * Determine whether the path is clockwise, using the control points.
88     *
89     * TODO: Given the skia is using inverted Y coordinate, shadow system needs
90     * to convert to the same coordinate to avoid the extra reverse.
91     *
92     * @param path The path to be examined.
93     */
94    static bool isClockwisePath(const SkPath &path);
95
96    /**
97     * Reverse the vertex array.
98     *
99     * @param polygon The vertex array to be reversed.
100     * @param len The length of the vertex array.
101     */
102    static void reverseVertexArray(Vertex* polygon, int len);
103
104    static int getExtraVertexNumber(const Vector2& vector1, const Vector2& vector2,
105            float divisor);
106
107    static void checkOverflow(int used, int total, const char* bufferName);
108}; // ShadowTessellator
109
110}; // namespace uirenderer
111}; // namespace android
112
113#endif // ANDROID_HWUI_SHADOW_TESSELLATOR_H
114