1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <math.h>
18#include <utils/Log.h>
19#include <utils/MathUtils.h>
20#include <utils/Trace.h>
21
22#include "AmbientShadow.h"
23#include "Properties.h"
24#include "ShadowTessellator.h"
25#include "SpotShadow.h"
26#include "Vector.h"
27
28namespace android {
29namespace uirenderer {
30
31void ShadowTessellator::tessellateAmbientShadow(bool isCasterOpaque, const Vector3* casterPolygon,
32                                                int casterVertexCount, const Vector3& centroid3d,
33                                                const Rect& casterBounds, const Rect& localClip,
34                                                float maxZ, VertexBuffer& shadowVertexBuffer) {
35    ATRACE_CALL();
36
37    // A bunch of parameters to tweak the shadow.
38    // TODO: Allow some of these changable by debug settings or APIs.
39    float heightFactor = 1.0f / 128;
40    const float geomFactor = 64;
41
42    if (CC_UNLIKELY(Properties::overrideAmbientRatio > 0.0f)) {
43        heightFactor *= Properties::overrideAmbientRatio;
44    }
45
46    Rect ambientShadowBounds(casterBounds);
47    ambientShadowBounds.outset(maxZ * geomFactor * heightFactor);
48
49    if (!localClip.intersects(ambientShadowBounds)) {
50#if DEBUG_SHADOW
51        ALOGD("Ambient shadow is out of clip rect!");
52#endif
53        return;
54    }
55
56    AmbientShadow::createAmbientShadow(isCasterOpaque, casterPolygon, casterVertexCount, centroid3d,
57                                       heightFactor, geomFactor, shadowVertexBuffer);
58}
59
60void ShadowTessellator::tessellateSpotShadow(bool isCasterOpaque, const Vector3* casterPolygon,
61                                             int casterVertexCount, const Vector3& casterCentroid,
62                                             const mat4& receiverTransform,
63                                             const Vector3& lightCenter, int lightRadius,
64                                             const Rect& casterBounds, const Rect& localClip,
65                                             VertexBuffer& shadowVertexBuffer) {
66    ATRACE_CALL();
67
68    Vector3 adjustedLightCenter(lightCenter);
69    if (CC_UNLIKELY(Properties::overrideLightPosY > 0)) {
70        adjustedLightCenter.y = -Properties::overrideLightPosY;  // negated since this shifts up
71    }
72    if (CC_UNLIKELY(Properties::overrideLightPosZ > 0)) {
73        adjustedLightCenter.z = Properties::overrideLightPosZ;
74    }
75
76#if DEBUG_SHADOW
77    ALOGD("light center %f %f %f %d", adjustedLightCenter.x, adjustedLightCenter.y,
78          adjustedLightCenter.z, lightRadius);
79#endif
80    if (isnan(adjustedLightCenter.x) || isnan(adjustedLightCenter.y) ||
81        isnan(adjustedLightCenter.z)) {
82        return;
83    }
84
85    // light position (because it's in local space) needs to compensate for receiver transform
86    // TODO: should apply to light orientation, not just position
87    Matrix4 reverseReceiverTransform;
88    reverseReceiverTransform.loadInverse(receiverTransform);
89    reverseReceiverTransform.mapPoint3d(adjustedLightCenter);
90
91    if (CC_UNLIKELY(Properties::overrideLightRadius > 0)) {
92        lightRadius = Properties::overrideLightRadius;
93    }
94
95    // Now light and caster are both in local space, we will check whether
96    // the shadow is within the clip area.
97    Rect lightRect = Rect(adjustedLightCenter.x - lightRadius, adjustedLightCenter.y - lightRadius,
98                          adjustedLightCenter.x + lightRadius, adjustedLightCenter.y + lightRadius);
99    lightRect.unionWith(localClip);
100    if (!lightRect.intersects(casterBounds)) {
101#if DEBUG_SHADOW
102        ALOGD("Spot shadow is out of clip rect!");
103#endif
104        return;
105    }
106
107    SpotShadow::createSpotShadow(isCasterOpaque, adjustedLightCenter, lightRadius, casterPolygon,
108                                 casterVertexCount, casterCentroid, shadowVertexBuffer);
109
110#if DEBUG_SHADOW
111    if (shadowVertexBuffer.getVertexCount() <= 0) {
112        ALOGD("Spot shadow generation failed %d", shadowVertexBuffer.getVertexCount());
113    }
114#endif
115}
116
117/**
118 * Calculate the centroid of a 2d polygon.
119 *
120 * @param poly The polygon, which is represented in a Vector2 array.
121 * @param polyLength The length of the polygon in terms of number of vertices.
122 * @return the centroid of the polygon.
123 */
124Vector2 ShadowTessellator::centroid2d(const Vector2* poly, int polyLength) {
125    double sumx = 0;
126    double sumy = 0;
127    int p1 = polyLength - 1;
128    double area = 0;
129    for (int p2 = 0; p2 < polyLength; p2++) {
130        double x1 = poly[p1].x;
131        double y1 = poly[p1].y;
132        double x2 = poly[p2].x;
133        double y2 = poly[p2].y;
134        double a = (x1 * y2 - x2 * y1);
135        sumx += (x1 + x2) * a;
136        sumy += (y1 + y2) * a;
137        area += a;
138        p1 = p2;
139    }
140
141    Vector2 centroid = poly[0];
142    if (area != 0) {
143        centroid = (Vector2){static_cast<float>(sumx / (3 * area)),
144                             static_cast<float>(sumy / (3 * area))};
145    } else {
146        ALOGW("Area is 0 while computing centroid!");
147    }
148    return centroid;
149}
150
151// Make sure p1 -> p2 is going CW around the poly.
152Vector2 ShadowTessellator::calculateNormal(const Vector2& p1, const Vector2& p2) {
153    Vector2 result = p2 - p1;
154    if (result.x != 0 || result.y != 0) {
155        result.normalize();
156        // Calculate the normal , which is CCW 90 rotate to the delta.
157        float tempy = result.y;
158        result.y = result.x;
159        result.x = -tempy;
160    }
161    return result;
162}
163
164int ShadowTessellator::getExtraVertexNumber(const Vector2& vector1, const Vector2& vector2,
165                                            float divisor) {
166    // When there is no distance difference, there is no need for extra vertices.
167    if (vector1.lengthSquared() == 0 || vector2.lengthSquared() == 0) {
168        return 0;
169    }
170    // The formula is :
171    // extraNumber = floor(acos(dot(n1, n2)) / (M_PI / EXTRA_VERTEX_PER_PI))
172    // The value ranges for each step are:
173    // dot( ) --- [-1, 1]
174    // acos( )     --- [0, M_PI]
175    // floor(...)  --- [0, EXTRA_VERTEX_PER_PI]
176    float dotProduct = vector1.dot(vector2);
177    // make sure that dotProduct value is in acsof input range [-1, 1]
178    dotProduct = MathUtils::clamp(dotProduct, -1.0f, 1.0f);
179    // TODO: Use look up table for the dotProduct to extraVerticesNumber
180    // computation, if needed.
181    float angle = acosf(dotProduct);
182    return (int)floor(angle / divisor);
183}
184
185void ShadowTessellator::checkOverflow(int used, int total, const char* bufferName) {
186    LOG_ALWAYS_FATAL_IF(used > total, "Error: %s overflow!!! used %d, total %d", bufferName, used,
187                        total);
188}
189
190};  // namespace uirenderer
191};  // namespace android
192