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- /*
- * Copyright 2017 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #include "include/core/SkMatrix.h"
- #include "include/core/SkPath.h"
- #include "include/core/SkRect.h"
- #include "src/core/SkDrawShadowInfo.h"
- #include "src/utils/SkPolyUtils.h"
- namespace SkDrawShadowMetrics {
- static SkScalar compute_z(SkScalar x, SkScalar y, const SkPoint3& params) {
- return x*params.fX + y*params.fY + params.fZ;
- }
- bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
- const SkMatrix& ctm, const SkPoint3& zPlaneParams,
- const SkRect& pathBounds, SkMatrix* shadowTransform, SkScalar* radius) {
- auto heightFunc = [zPlaneParams] (SkScalar x, SkScalar y) {
- return zPlaneParams.fX*x + zPlaneParams.fY*y + zPlaneParams.fZ;
- };
- SkScalar occluderHeight = heightFunc(pathBounds.centerX(), pathBounds.centerY());
- if (!ctm.hasPerspective()) {
- SkScalar scale;
- SkVector translate;
- SkDrawShadowMetrics::GetSpotParams(occluderHeight, lightPos.fX, lightPos.fY, lightPos.fZ,
- lightRadius, radius, &scale, &translate);
- shadowTransform->setScaleTranslate(scale, scale, translate.fX, translate.fY);
- shadowTransform->preConcat(ctm);
- } else {
- if (SkScalarNearlyZero(pathBounds.width()) || SkScalarNearlyZero(pathBounds.height())) {
- return false;
- }
- // get rotated quad in 3D
- SkPoint pts[4];
- ctm.mapRectToQuad(pts, pathBounds);
- // No shadows for bowties or other degenerate cases
- if (!SkIsConvexPolygon(pts, 4)) {
- return false;
- }
- SkPoint3 pts3D[4];
- SkScalar z = heightFunc(pathBounds.fLeft, pathBounds.fTop);
- pts3D[0].set(pts[0].fX, pts[0].fY, z);
- z = heightFunc(pathBounds.fRight, pathBounds.fTop);
- pts3D[1].set(pts[1].fX, pts[1].fY, z);
- z = heightFunc(pathBounds.fRight, pathBounds.fBottom);
- pts3D[2].set(pts[2].fX, pts[2].fY, z);
- z = heightFunc(pathBounds.fLeft, pathBounds.fBottom);
- pts3D[3].set(pts[3].fX, pts[3].fY, z);
- // project from light through corners to z=0 plane
- for (int i = 0; i < 4; ++i) {
- SkScalar dz = lightPos.fZ - pts3D[i].fZ;
- // light shouldn't be below or at a corner's z-location
- if (dz <= SK_ScalarNearlyZero) {
- return false;
- }
- SkScalar zRatio = pts3D[i].fZ / dz;
- pts3D[i].fX -= (lightPos.fX - pts3D[i].fX)*zRatio;
- pts3D[i].fY -= (lightPos.fY - pts3D[i].fY)*zRatio;
- pts3D[i].fZ = SK_Scalar1;
- }
- // Generate matrix that projects from [-1,1]x[-1,1] square to projected quad
- SkPoint3 h0, h1, h2;
- // Compute homogenous crossing point between top and bottom edges (gives new x-axis).
- h0 = (pts3D[1].cross(pts3D[0])).cross(pts3D[2].cross(pts3D[3]));
- // Compute homogenous crossing point between left and right edges (gives new y-axis).
- h1 = (pts3D[0].cross(pts3D[3])).cross(pts3D[1].cross(pts3D[2]));
- // Compute homogenous crossing point between diagonals (gives new origin).
- h2 = (pts3D[0].cross(pts3D[2])).cross(pts3D[1].cross(pts3D[3]));
- // If h2 is a vector (z=0 in 2D homogeneous space), that means that at least
- // two of the quad corners are coincident and we don't have a realistic projection
- if (SkScalarNearlyZero(h2.fZ)) {
- return false;
- }
- // In some cases the crossing points are in the wrong direction
- // to map (-1,-1) to pts3D[0], so we need to correct for that.
- // Want h0 to be to the right of the left edge.
- SkVector3 v = pts3D[3] - pts3D[0];
- SkVector3 w = h0 - pts3D[0];
- SkScalar perpDot = v.fX*w.fY - v.fY*w.fX;
- if (perpDot > 0) {
- h0 = -h0;
- }
- // Want h1 to be above the bottom edge.
- v = pts3D[1] - pts3D[0];
- perpDot = v.fX*w.fY - v.fY*w.fX;
- if (perpDot < 0) {
- h1 = -h1;
- }
- shadowTransform->setAll(h0.fX / h2.fZ, h1.fX / h2.fZ, h2.fX / h2.fZ,
- h0.fY / h2.fZ, h1.fY / h2.fZ, h2.fY / h2.fZ,
- h0.fZ / h2.fZ, h1.fZ / h2.fZ, 1);
- // generate matrix that transforms from bounds to [-1,1]x[-1,1] square
- SkMatrix toHomogeneous;
- SkScalar xScale = 2/(pathBounds.fRight - pathBounds.fLeft);
- SkScalar yScale = 2/(pathBounds.fBottom - pathBounds.fTop);
- toHomogeneous.setAll(xScale, 0, -xScale*pathBounds.fLeft - 1,
- 0, yScale, -yScale*pathBounds.fTop - 1,
- 0, 0, 1);
- shadowTransform->preConcat(toHomogeneous);
- *radius = SkDrawShadowMetrics::SpotBlurRadius(occluderHeight, lightPos.fZ, lightRadius);
- }
- return true;
- }
- void GetLocalBounds(const SkPath& path, const SkDrawShadowRec& rec, const SkMatrix& ctm,
- SkRect* bounds) {
- SkRect ambientBounds = path.getBounds();
- SkScalar occluderZ;
- if (SkScalarNearlyZero(rec.fZPlaneParams.fX) && SkScalarNearlyZero(rec.fZPlaneParams.fY)) {
- occluderZ = rec.fZPlaneParams.fZ;
- } else {
- occluderZ = compute_z(ambientBounds.fLeft, ambientBounds.fTop, rec.fZPlaneParams);
- occluderZ = SkTMax(occluderZ, compute_z(ambientBounds.fRight, ambientBounds.fTop,
- rec.fZPlaneParams));
- occluderZ = SkTMax(occluderZ, compute_z(ambientBounds.fLeft, ambientBounds.fBottom,
- rec.fZPlaneParams));
- occluderZ = SkTMax(occluderZ, compute_z(ambientBounds.fRight, ambientBounds.fBottom,
- rec.fZPlaneParams));
- }
- SkScalar ambientBlur;
- SkScalar spotBlur;
- SkScalar spotScale;
- SkPoint spotOffset;
- if (ctm.hasPerspective()) {
- // transform ambient and spot bounds into device space
- ctm.mapRect(&ambientBounds);
- // get ambient blur (in device space)
- ambientBlur = SkDrawShadowMetrics::AmbientBlurRadius(occluderZ);
- // get spot params (in device space)
- SkPoint devLightPos = SkPoint::Make(rec.fLightPos.fX, rec.fLightPos.fY);
- ctm.mapPoints(&devLightPos, 1);
- SkDrawShadowMetrics::GetSpotParams(occluderZ, devLightPos.fX, devLightPos.fY,
- rec.fLightPos.fZ, rec.fLightRadius,
- &spotBlur, &spotScale, &spotOffset);
- } else {
- SkScalar devToSrcScale = SkScalarInvert(ctm.getMinScale());
- // get ambient blur (in local space)
- SkScalar devSpaceAmbientBlur = SkDrawShadowMetrics::AmbientBlurRadius(occluderZ);
- ambientBlur = devSpaceAmbientBlur*devToSrcScale;
- // get spot params (in local space)
- SkDrawShadowMetrics::GetSpotParams(occluderZ, rec.fLightPos.fX, rec.fLightPos.fY,
- rec.fLightPos.fZ, rec.fLightRadius,
- &spotBlur, &spotScale, &spotOffset);
- // convert spot blur to local space
- spotBlur *= devToSrcScale;
- }
- // in both cases, adjust ambient and spot bounds
- SkRect spotBounds = ambientBounds;
- ambientBounds.outset(ambientBlur, ambientBlur);
- spotBounds.fLeft *= spotScale;
- spotBounds.fTop *= spotScale;
- spotBounds.fRight *= spotScale;
- spotBounds.fBottom *= spotScale;
- spotBounds.offset(spotOffset.fX, spotOffset.fY);
- spotBounds.outset(spotBlur, spotBlur);
- // merge bounds
- *bounds = ambientBounds;
- bounds->join(spotBounds);
- // outset a bit to account for floating point error
- bounds->outset(1, 1);
- // if perspective, transform back to src space
- if (ctm.hasPerspective()) {
- // TODO: create tighter mapping from dev rect back to src rect
- SkMatrix inverse;
- if (ctm.invert(&inverse)) {
- inverse.mapRect(bounds);
- }
- }
- }
- }
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