void ParticleSystem::Node::update(const std::vector<Particle>& set) {
if (m_geometry.vertexDataSize() < 4 * set.size()) {
m_geometry.allocate(set.size() * 4 * 2, set.size() * 6 * 2 - 2);
generateTriangleStrip(m_geometry.indexData<GLuint>(),
m_geometry.indexDataSize());
}
Vertex* array = m_geometry.vertexData<Vertex>();
int it = 0;
for (const Particle& p : set) {
array[4 * it + 0] = Vertex(QPointF(p.x - p.r, p.y - p.r), QPointF(0, 0), p);
array[4 * it + 1] = Vertex(QPointF(p.x + p.r, p.y - p.r), QPointF(1, 0), p);
array[4 * it + 2] = Vertex(QPointF(p.x - p.r, p.y + p.r), QPointF(0, 1), p);
array[4 * it + 3] = Vertex(QPointF(p.x + p.r, p.y + p.r), QPointF(1, 1), p);
it++;
}
m_geometry.setVertexCount(set.size() * 4);
m_geometry.setIndexCount(set.size() * 6 - 2);
m_geometry.updateVertexData();
}
/**
* Generate the shadow spot light of shape lightPoly and a object poly
*
* @param isCasterOpaque whether the caster is opaque
* @param lightCenter the center of the light
* @param lightSize the radius of the light
* @param poly x,y,z vertexes of a convex polygon that occludes the light source
* @param polyLength number of vertexes of the occluding polygon
* @param shadowTriangleStrip return an (x,y,alpha) triangle strip representing the shadow. Return
* empty strip if error.
*/
void SpotShadow::createSpotShadow(bool isCasterOpaque, const Vector3& lightCenter,
float lightSize, const Vector3* poly, int polyLength, const Vector3& polyCentroid,
VertexBuffer& shadowTriangleStrip) {
if (CC_UNLIKELY(lightCenter.z <= 0)) {
ALOGW("Relative Light Z is not positive. No spot shadow!");
return;
}
if (CC_UNLIKELY(polyLength < 3)) {
#if DEBUG_SHADOW
ALOGW("Invalid polygon length. No spot shadow!");
#endif
return;
}
OutlineData outlineData[polyLength];
Vector2 outlineCentroid;
// Calculate the projected outline for each polygon's vertices from the light center.
//
// O Light
// /
// /
// . Polygon vertex
// /
// /
// O Outline vertices
//
// Ratio = (Poly - Outline) / (Light - Poly)
// Outline.x = Poly.x - Ratio * (Light.x - Poly.x)
// Outline's radius / Light's radius = Ratio
// Compute the last outline vertex to make sure we can get the normal and outline
// in one single loop.
projectCasterToOutline(outlineData[polyLength - 1].position, lightCenter,
poly[polyLength - 1]);
// Take the outline's polygon, calculate the normal for each outline edge.
int currentNormalIndex = polyLength - 1;
int nextNormalIndex = 0;
for (int i = 0; i < polyLength; i++) {
float ratioZ = projectCasterToOutline(outlineData[i].position,
lightCenter, poly[i]);
outlineData[i].radius = ratioZ * lightSize;
outlineData[currentNormalIndex].normal = ShadowTessellator::calculateNormal(
outlineData[currentNormalIndex].position,
outlineData[nextNormalIndex].position);
currentNormalIndex = (currentNormalIndex + 1) % polyLength;
nextNormalIndex++;
}
projectCasterToOutline(outlineCentroid, lightCenter, polyCentroid);
int penumbraIndex = 0;
// Then each polygon's vertex produce at minmal 2 penumbra vertices.
// Since the size can be dynamic here, we keep track of the size and update
// the real size at the end.
int allocatedPenumbraLength = 2 * polyLength + SPOT_MAX_EXTRA_CORNER_VERTEX_NUMBER;
Vector2 penumbra[allocatedPenumbraLength];
int totalExtraCornerSliceNumber = 0;
Vector2 umbra[polyLength];
// When centroid is covered by all circles from outline, then we consider
// the umbra is invalid, and we will tune down the shadow strength.
bool hasValidUmbra = true;
// We need the minimal of RaitoVI to decrease the spot shadow strength accordingly.
float minRaitoVI = FLT_MAX;
for (int i = 0; i < polyLength; i++) {
// Generate all the penumbra's vertices only using the (outline vertex + normal * radius)
// There is no guarantee that the penumbra is still convex, but for
// each outline vertex, it will connect to all its corresponding penumbra vertices as
// triangle fans. And for neighber penumbra vertex, it will be a trapezoid.
//
// Penumbra Vertices marked as Pi
// Outline Vertices marked as Vi
// (P3)
// (P2) | ' (P4)
// (P1)' | | '
// ' | | '
// (P0) ------------------------------------------------(P5)
// | (V0) |(V1)
// | |
// | |
// | |
// | |
// | |
// | |
// | |
// | |
// (V3)-----------------------------------(V2)
int preNormalIndex = (i + polyLength - 1) % polyLength;
const Vector2& previousNormal = outlineData[preNormalIndex].normal;
const Vector2& currentNormal = outlineData[i].normal;
// Depending on how roundness we want for each corner, we can subdivide
// further here and/or introduce some heuristic to decide how much the
// subdivision should be.
int currentExtraSliceNumber = ShadowTessellator::getExtraVertexNumber(
previousNormal, currentNormal, SPOT_CORNER_RADIANS_DIVISOR);
int currentCornerSliceNumber = 1 + currentExtraSliceNumber;
totalExtraCornerSliceNumber += currentExtraSliceNumber;
#if DEBUG_SHADOW
ALOGD("currentExtraSliceNumber should be %d", currentExtraSliceNumber);
ALOGD("currentCornerSliceNumber should be %d", currentCornerSliceNumber);
ALOGD("totalCornerSliceNumber is %d", totalExtraCornerSliceNumber);
#endif
if (CC_UNLIKELY(totalExtraCornerSliceNumber > SPOT_MAX_EXTRA_CORNER_VERTEX_NUMBER)) {
currentCornerSliceNumber = 1;
}
for (int k = 0; k <= currentCornerSliceNumber; k++) {
Vector2 avgNormal =
(previousNormal * (currentCornerSliceNumber - k) + currentNormal * k) /
currentCornerSliceNumber;
avgNormal.normalize();
penumbra[penumbraIndex++] = outlineData[i].position +
avgNormal * outlineData[i].radius;
}
// Compute the umbra by the intersection from the outline's centroid!
//
// (V) ------------------------------------
// | ' |
// | ' |
// | ' (I) |
// | ' |
// | ' (C) |
// | |
// | |
// | |
// | |
// ------------------------------------
//
// Connect a line b/t the outline vertex (V) and the centroid (C), it will
// intersect with the outline vertex's circle at point (I).
// Now, ratioVI = VI / VC, ratioIC = IC / VC
// Then the intersetion point can be computed as Ixy = Vxy * ratioIC + Cxy * ratioVI;
//
// When all of the outline circles cover the the outline centroid, (like I is
// on the other side of C), there is no real umbra any more, so we just fake
// a small area around the centroid as the umbra, and tune down the spot
// shadow's umbra strength to simulate the effect the whole shadow will
// become lighter in this case.
// The ratio can be simulated by using the inverse of maximum of ratioVI for
// all (V).
float distOutline = (outlineData[i].position - outlineCentroid).length();
if (CC_UNLIKELY(distOutline == 0)) {
// If the outline has 0 area, then there is no spot shadow anyway.
ALOGW("Outline has 0 area, no spot shadow!");
return;
}
float ratioVI = outlineData[i].radius / distOutline;
minRaitoVI = MathUtils::min(minRaitoVI, ratioVI);
if (ratioVI >= (1 - FAKE_UMBRA_SIZE_RATIO)) {
ratioVI = (1 - FAKE_UMBRA_SIZE_RATIO);
}
// When we know we don't have valid umbra, don't bother to compute the
// values below. But we can't skip the loop yet since we want to know the
// maximum ratio.
float ratioIC = 1 - ratioVI;
umbra[i] = outlineData[i].position * ratioIC + outlineCentroid * ratioVI;
}
hasValidUmbra = (minRaitoVI <= 1.0);
float shadowStrengthScale = 1.0;
if (!hasValidUmbra) {
#if DEBUG_SHADOW
ALOGW("The object is too close to the light or too small, no real umbra!");
#endif
for (int i = 0; i < polyLength; i++) {
umbra[i] = outlineData[i].position * FAKE_UMBRA_SIZE_RATIO +
outlineCentroid * (1 - FAKE_UMBRA_SIZE_RATIO);
}
shadowStrengthScale = 1.0 / minRaitoVI;
}
int penumbraLength = penumbraIndex;
int umbraLength = polyLength;
#if DEBUG_SHADOW
ALOGD("penumbraLength is %d , allocatedPenumbraLength %d", penumbraLength, allocatedPenumbraLength);
dumpPolygon(poly, polyLength, "input poly");
dumpPolygon(penumbra, penumbraLength, "penumbra");
dumpPolygon(umbra, umbraLength, "umbra");
ALOGD("hasValidUmbra is %d and shadowStrengthScale is %f", hasValidUmbra, shadowStrengthScale);
#endif
// The penumbra and umbra needs to be in convex shape to keep consistency
// and quality.
// Since we are still shooting rays to penumbra, it needs to be convex.
// Umbra can be represented as a fan from the centroid, but visually umbra
// looks nicer when it is convex.
Vector2 finalUmbra[umbraLength];
Vector2 finalPenumbra[penumbraLength];
int finalUmbraLength = hull(umbra, umbraLength, finalUmbra);
int finalPenumbraLength = hull(penumbra, penumbraLength, finalPenumbra);
generateTriangleStrip(isCasterOpaque, shadowStrengthScale, finalPenumbra,
finalPenumbraLength, finalUmbra, finalUmbraLength, poly, polyLength,
shadowTriangleStrip, outlineCentroid);
}
