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/*
* 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"
/**
* Extra vertices for the corner for smoother corner.
* Only for outer vertices.
* Note that we use such extra memory to avoid an extra loop.
*/
// For half circle, we could add EXTRA_VERTEX_PER_PI vertices.
// Set to 1 if we don't want to have any.
#define EXTRA_CORNER_VERTEX_PER_PI 12
// For the whole polygon, the sum of all the deltas b/t normals is 2 * M_PI,
// therefore, the maximum number of extra vertices will be twice bigger.
#define MAX_EXTRA_CORNER_VERTEX_NUMBER (2 * EXTRA_CORNER_VERTEX_PER_PI)
// For each RADIANS_DIVISOR, we would allocate one more vertex b/t the normals.
#define CORNER_RADIANS_DIVISOR (M_PI / EXTRA_CORNER_VERTEX_PER_PI)
/**
* Extra vertices for the Edge for interpolation artifacts.
* Same value for both inner and outer vertices.
*/
#define EXTRA_EDGE_VERTEX_PER_PI 50
#define MAX_EXTRA_EDGE_VERTEX_NUMBER (2 * EXTRA_EDGE_VERTEX_PER_PI)
#define EDGE_RADIANS_DIVISOR (M_PI / EXTRA_EDGE_VERTEX_PER_PI)
/**
* Other constants:
*/
// For the edge of the penumbra, the opacity is 0.
#define OUTER_OPACITY (0.0f)
// Once the alpha difference is greater than this threshold, we will allocate extra
// edge vertices.
// If this is set to negative value, then all the edge will be tessellated.
#define ALPHA_THRESHOLD (0.1f / 255.0f)
#include <math.h>
#include <utils/Log.h>
#include <utils/Vector.h>
#include "AmbientShadow.h"
#include "ShadowTessellator.h"
#include "Vertex.h"
#include "utils/MathUtils.h"
namespace android {
namespace uirenderer {
/**
* Local utility functions.
*/
inline Vector2 getNormalFromVertices(const Vector3* vertices, int current, int next) {
// Convert from Vector3 to Vector2 first.
Vector2 currentVertex = { vertices[current].x, vertices[current].y };
Vector2 nextVertex = { vertices[next].x, vertices[next].y };
return ShadowTessellator::calculateNormal(currentVertex, nextVertex);
}
// The input z value will be converted to be non-negative inside.
// The output must be ranged from 0 to 1.
inline float getAlphaFromFactoredZ(float factoredZ) {
return 1.0 / (1 + MathUtils::max(factoredZ, 0.0f));
}
inline float getTransformedAlphaFromAlpha(float alpha) {
return acosf(1.0f - 2.0f * alpha);
}
// The output is ranged from 0 to M_PI.
inline float getTransformedAlphaFromFactoredZ(float factoredZ) {
return getTransformedAlphaFromAlpha(getAlphaFromFactoredZ(factoredZ));
}
inline int getExtraVertexNumber(const Vector2& vector1, const Vector2& vector2,
float divisor) {
// When there is no distance difference, there is no need for extra vertices.
if (vector1.lengthSquared() == 0 || vector2.lengthSquared() == 0) {
return 0;
}
// The formula is :
// extraNumber = floor(acos(dot(n1, n2)) / (M_PI / EXTRA_VERTEX_PER_PI))
// The value ranges for each step are:
// dot( ) --- [-1, 1]
// acos( ) --- [0, M_PI]
// floor(...) --- [0, EXTRA_VERTEX_PER_PI]
float dotProduct = vector1.dot(vector2);
// TODO: Use look up table for the dotProduct to extraVerticesNumber
// computation, if needed.
float angle = acosf(dotProduct);
return (int) floor(angle / divisor);
}
inline void checkOverflow(int used, int total, const char* bufferName) {
LOG_ALWAYS_FATAL_IF(used > total, "Error: %s overflow!!! used %d, total %d",
bufferName, used, total);
}
inline int getEdgeExtraAndUpdateSpike(Vector2* currentSpike,
const Vector3& secondVertex, const Vector3& centroid) {
Vector2 secondSpike = {secondVertex.x - centroid.x, secondVertex.y - centroid.y};
secondSpike.normalize();
int result = getExtraVertexNumber(secondSpike, *currentSpike, EDGE_RADIANS_DIVISOR);
*currentSpike = secondSpike;
return result;
}
// Given the caster's vertex count, compute all the buffers size depending on
// whether or not the caster is opaque.
inline void computeBufferSize(int* totalVertexCount, int* totalIndexCount,
int* totalUmbraCount, int casterVertexCount, bool isCasterOpaque) {
// Compute the size of the vertex buffer.
int outerVertexCount = casterVertexCount * 2 + MAX_EXTRA_CORNER_VERTEX_NUMBER +
MAX_EXTRA_EDGE_VERTEX_NUMBER;
int innerVertexCount = casterVertexCount + MAX_EXTRA_EDGE_VERTEX_NUMBER;
*totalVertexCount = outerVertexCount + innerVertexCount;
// Compute the size of the index buffer.
*totalIndexCount = 2 * outerVertexCount + 2;
// Compute the size of the umber buffer.
// For translucent object, keep track of the umbra(inner) vertex in order to draw
// inside. We only need to store the index information.
*totalUmbraCount = 0;
if (!isCasterOpaque) {
// Add the centroid if occluder is translucent.
*totalVertexCount++;
*totalIndexCount += 2 * innerVertexCount + 1;
*totalUmbraCount = innerVertexCount;
}
}
inline bool needsExtraForEdge(float firstAlpha, float secondAlpha) {
return abs(firstAlpha - secondAlpha) > ALPHA_THRESHOLD;
}
/**
* Calculate the shadows as a triangle strips while alpha value as the
* shadow values.
*
* @param isCasterOpaque Whether the caster is opaque.
* @param vertices The shadow caster's polygon, which is represented in a Vector3
* array.
* @param vertexCount The length of caster's polygon in terms of number of
* vertices.
* @param centroid3d The centroid of the shadow caster.
* @param heightFactor The factor showing the higher the object, the lighter the
* shadow.
* @param geomFactor The factor scaling the geometry expansion along the normal.
*
* @param shadowVertexBuffer Return an floating point array of (x, y, a)
* triangle strips mode.
*
* An simple illustration:
* For now let's mark the outer vertex as Pi, the inner as Vi, the centroid as C.
*
* First project the occluder to the Z=0 surface.
* Then we got all the inner vertices. And we compute the normal for each edge.
* According to the normal, we generate outer vertices. E.g: We generate P1 / P4
* as extra corner vertices to make the corner looks round and smoother.
*
* Due to the fact that the alpha is not linear interpolated along the inner
* edge, when the alpha is different, we may add extra vertices such as P2.1, P2.2,
* V0.1, V0.2 to avoid the visual artifacts.
*
* (P3)
* (P2) (P2.1) (P2.2) | ' (P4)
* (P1)' | | | | '
* ' | | | | '
* (P0) ------------------------------------------------(P5)
* | (V0) (V0.1) (V0.2) |(V1)
* | |
* | |
* | (C) |
* | |
* | |
* | |
* | |
* (V3)-----------------------------------(V2)
*/
void AmbientShadow::createAmbientShadow(bool isCasterOpaque,
const Vector3* casterVertices, int casterVertexCount, const Vector3& centroid3d,
float heightFactor, float geomFactor, VertexBuffer& shadowVertexBuffer) {
shadowVertexBuffer.setMode(VertexBuffer::kIndices);
// In order to computer the outer vertices in one loop, we need pre-compute
// the normal by the vertex (n - 1) to vertex 0, and the spike and alpha value
// for vertex 0.
Vector2 previousNormal = getNormalFromVertices(casterVertices,
casterVertexCount - 1 , 0);
Vector2 currentSpike = {casterVertices[0].x - centroid3d.x,
casterVertices[0].y - centroid3d.y};
currentSpike.normalize();
float currentAlpha = getAlphaFromFactoredZ(casterVertices[0].z * heightFactor);
// Preparing all the output data.
int totalVertexCount, totalIndexCount, totalUmbraCount;
computeBufferSize(&totalVertexCount, &totalIndexCount, &totalUmbraCount,
casterVertexCount, isCasterOpaque);
AlphaVertex* shadowVertices =
shadowVertexBuffer.alloc<AlphaVertex>(totalVertexCount);
int vertexBufferIndex = 0;
uint16_t* indexBuffer = shadowVertexBuffer.allocIndices<uint16_t>(totalIndexCount);
int indexBufferIndex = 0;
uint16_t umbraVertices[totalUmbraCount];
int umbraIndex = 0;
for (int i = 0; i < casterVertexCount; i++) {
// Corner: first figure out the extra vertices we need for the corner.
const Vector3& innerVertex = casterVertices[i];
Vector2 currentNormal = getNormalFromVertices(casterVertices, i,
(i + 1) % casterVertexCount);
int extraVerticesNumber = getExtraVertexNumber(currentNormal, previousNormal,
CORNER_RADIANS_DIVISOR);
float expansionDist = innerVertex.z * heightFactor * geomFactor;
const int cornerSlicesNumber = extraVerticesNumber + 1; // Minimal as 1.
#if DEBUG_SHADOW
ALOGD("cornerSlicesNumber is %d", cornerSlicesNumber);
#endif
// Corner: fill the corner Vertex Buffer(VB) and Index Buffer(IB).
// We fill the inner vertex first, such that we can fill the index buffer
// inside the loop.
int currentInnerVertexIndex = vertexBufferIndex;
if (!isCasterOpaque) {
umbraVertices[umbraIndex++] = vertexBufferIndex;
}
AlphaVertex::set(&shadowVertices[vertexBufferIndex++], casterVertices[i].x,
casterVertices[i].y,
getTransformedAlphaFromAlpha(currentAlpha));
const Vector3& innerStart = casterVertices[i];
// outerStart is the first outer vertex for this inner vertex.
// outerLast is the last outer vertex for this inner vertex.
Vector2 outerStart = {0, 0};
Vector2 outerLast = {0, 0};
// This will create vertices from [0, cornerSlicesNumber] inclusively,
// which means minimally 2 vertices even without the extra ones.
for (int j = 0; j <= cornerSlicesNumber; j++) {
Vector2 averageNormal =
previousNormal * (cornerSlicesNumber - j) + currentNormal * j;
averageNormal /= cornerSlicesNumber;
averageNormal.normalize();
Vector2 outerVertex;
outerVertex.x = innerVertex.x + averageNormal.x * expansionDist;
outerVertex.y = innerVertex.y + averageNormal.y * expansionDist;
indexBuffer[indexBufferIndex++] = vertexBufferIndex;
indexBuffer[indexBufferIndex++] = currentInnerVertexIndex;
AlphaVertex::set(&shadowVertices[vertexBufferIndex++], outerVertex.x,
outerVertex.y, OUTER_OPACITY);
if (j == 0) {
outerStart = outerVertex;
} else if (j == cornerSlicesNumber) {
outerLast = outerVertex;
}
}
previousNormal = currentNormal;
// Edge: first figure out the extra vertices needed for the edge.
const Vector3& innerNext = casterVertices[(i + 1) % casterVertexCount];
float nextAlpha = getAlphaFromFactoredZ(innerNext.z * heightFactor);
if (needsExtraForEdge(currentAlpha, nextAlpha)) {
// TODO: See if we can / should cache this outer vertex across the loop.
Vector2 outerNext;
float expansionDist = innerNext.z * heightFactor * geomFactor;
outerNext.x = innerNext.x + currentNormal.x * expansionDist;
outerNext.y = innerNext.y + currentNormal.y * expansionDist;
// Compute the angle and see how many extra points we need.
int extraVerticesNumber = getEdgeExtraAndUpdateSpike(&currentSpike,
innerNext, centroid3d);
#if DEBUG_SHADOW
ALOGD("extraVerticesNumber %d for edge %d", extraVerticesNumber, i);
#endif
// Edge: fill the edge's VB and IB.
// This will create vertices pair from [1, extraVerticesNumber - 1].
// If there is no extra vertices created here, the edge will be drawn
// as just 2 triangles.
for (int k = 1; k < extraVerticesNumber; k++) {
int startWeight = extraVerticesNumber - k;
Vector2 currentOuter =
(outerLast * startWeight + outerNext * k) / extraVerticesNumber;
indexBuffer[indexBufferIndex++] = vertexBufferIndex;
AlphaVertex::set(&shadowVertices[vertexBufferIndex++], currentOuter.x,
currentOuter.y, OUTER_OPACITY);
if (!isCasterOpaque) {
umbraVertices[umbraIndex++] = vertexBufferIndex;
}
Vector3 currentInner =
(innerStart * startWeight + innerNext * k) / extraVerticesNumber;
indexBuffer[indexBufferIndex++] = vertexBufferIndex;
AlphaVertex::set(&shadowVertices[vertexBufferIndex++], currentInner.x,
currentInner.y,
getTransformedAlphaFromFactoredZ(currentInner.z * heightFactor));
}
}
currentAlpha = nextAlpha;
}
indexBuffer[indexBufferIndex++] = 1;
indexBuffer[indexBufferIndex++] = 0;
if (!isCasterOpaque) {
// Add the centroid as the last one in the vertex buffer.
float centroidOpacity =
getTransformedAlphaFromFactoredZ(centroid3d.z * heightFactor);
int centroidIndex = vertexBufferIndex;
AlphaVertex::set(&shadowVertices[vertexBufferIndex++], centroid3d.x,
centroid3d.y, centroidOpacity);
for (int i = 0; i < umbraIndex; i++) {
// Note that umbraVertices[0] is always 0.
// So the start and the end of the umbra are using the "0".
// And penumbra ended with 0, so a degenerated triangle is formed b/t
// the umbra and penumbra.
indexBuffer[indexBufferIndex++] = umbraVertices[i];
indexBuffer[indexBufferIndex++] = centroidIndex;
}
indexBuffer[indexBufferIndex++] = 0;
}
// At the end, update the real index and vertex buffer size.
shadowVertexBuffer.updateVertexCount(vertexBufferIndex);
shadowVertexBuffer.updateIndexCount(indexBufferIndex);
checkOverflow(vertexBufferIndex, totalVertexCount, "Vertex Buffer");
checkOverflow(indexBufferIndex, totalIndexCount, "Index Buffer");
checkOverflow(umbraIndex, totalUmbraCount, "Umbra Buffer");
#if DEBUG_SHADOW
for (int i = 0; i < vertexBufferIndex; i++) {
ALOGD("vertexBuffer i %d, (%f, %f %f)", i, shadowVertices[i].x, shadowVertices[i].y,
shadowVertices[i].alpha);
}
for (int i = 0; i < indexBufferIndex; i++) {
ALOGD("indexBuffer i %d, indexBuffer[i] %d", i, indexBuffer[i]);
}
#endif
}
}; // namespace uirenderer
}; // namespace android