Add alternative spot shadow to Android shadow sample

samplecode/SampleAndroidShadows.cpp

 
 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SampleCode.h"
 #include "SkBlurMask.h"
 #include "SkBlurMaskFilter.h"
 #include "SkCanvas.h"
 #include "SkGaussianEdgeShader.h"
 #include "SkPath.h"
 #include "SkPoint3.h"
 #include "SkUtils.h"
 #include "SkView.h"
 #include "sk_tool_utils.h"
 
 ////////////////////////////////////////////////////////////////////////////
 
 class ShadowsView : public SampleView {
     SkPath    fRectPath;
     SkPath    fRRPath;
     SkPath    fCirclePath;
     SkPoint3  fLightPos;
 
     bool      fShowAmbient;
-    bool      fUseAltAmbient;
     bool      fShowSpot;
+    bool      fUseAlt;
     bool      fShowObject;
 
 public:
     ShadowsView() 
         : fShowAmbient(true)
-        , fUseAltAmbient(true)
         , fShowSpot(true)
+        , fUseAlt(true)
         , fShowObject(true) {}
 
 protected:
     void onOnceBeforeDraw() override {
         fCirclePath.addCircle(0, 0, 50);
         fRectPath.addRect(SkRect::MakeXYWH(-100, -50, 200, 100));
         fRRPath.addRRect(SkRRect::MakeRectXY(SkRect::MakeXYWH(-100, -50, 200, 100), 4, 4));
-        fLightPos = SkPoint3::Make(-220, -330, 150);
+        fLightPos = SkPoint3::Make(-2, -2, 6);
     }
 
     // overrides from SkEventSink
     bool onQuery(SkEvent* evt) override {
         if (SampleCode::TitleQ(*evt)) {
             SampleCode::TitleR(evt, "AndroidShadows");
             return true;
         }
 
         SkUnichar uni;
         if (SampleCode::CharQ(*evt, &uni)) {
             switch (uni) {
                 case 'B':
                     fShowAmbient = !fShowAmbient;
                     break;
-                case 'T':
-                    fUseAltAmbient = !fUseAltAmbient;
-                    break;
                 case 'S':
                     fShowSpot = !fShowSpot;
                     break;
+                case 'T':
+                    fUseAlt = !fUseAlt;
+                    break;
                 case 'O':
                     fShowObject = !fShowObject;
                     break;
                 case '>':
                     fLightPos.fZ += 10;
                     break;
                 case '<':
                     fLightPos.fZ -= 10;
                     break;
                 default:
@@ skipping 60 matching lines @@
 #endif
     }
 
     void drawAmbientShadowAlt(SkCanvas* canvas, const SkPath& path, SkScalar zValue,
                               SkScalar ambientAlpha) {
 
         if (ambientAlpha <= 0) {
             return;
         }
 
+        SkRect pathRect;
+        SkRRect pathRRect;
+        if ((!path.isOval(&pathRect) || pathRect.width() != pathRect.height()) &&
+            (!path.isRRect(&pathRRect) || !pathRRect.allCornersCircular()) &&
+            !path.isRect(&pathRect)) {

[robertphillips, 2016/08/17 15:44:40]

this-> ?

[jvanverth1, 2016/08/17 16:19:27]

Done.

+            drawAmbientShadow(canvas, path, zValue, ambientAlpha);
+            return;
+        }
+
         const SkScalar kHeightFactor = 1.f / 128.f;
         const SkScalar kGeomFactor = 64;
 
         SkScalar umbraAlpha = 1 / (1 + SkMaxScalar(zValue*kHeightFactor, 0));
         SkScalar radius = zValue*kHeightFactor*kGeomFactor;
 

[robertphillips, 2016/08/17 15:44:39]

stroke shape -> "coverage" RRect ?

[jvanverth1, 2016/08/17 16:19:28]

Done. And thanks -- there was a bug here.

-        // fast path
-        SkRect pathRect;
-        SkRRect pathRRect;
-        if ((path.isOval(&pathRect) && pathRect.width() == pathRect.height()) ||
-            (path.isRRect(&pathRRect) && pathRRect.allCornersCircular()) ||
-            path.isRect(&pathRect)) {
-
-            // For all of these, we outset the rect by half the radius to get our stroke shape.
-            if (path.isOval(nullptr)) {
-                pathRect.outset(0.5f*radius, 0.5f*radius);
-                pathRRect = SkRRect::MakeOval(pathRect);
-            } else if (path.isRect(nullptr)) {
-                pathRect.outset(0.5f*radius, 0.5f*radius);
-                pathRRect = SkRRect::MakeRectXY(pathRect, 0.5f*radius, 0.5f*radius);
-            } else {
-                pathRRect.outset(0.5f*radius, 0.5f*radius);
-            }
-
-            SkPaint paint;
-            paint.setAntiAlias(true);
-            paint.setColor(SkColorSetARGB((unsigned char)(ambientAlpha*umbraAlpha*255.999f), 
-                                          0, 0, 0));
-            paint.setStrokeWidth(radius);
-            paint.setStyle(SkPaint::kStroke_Style);
-
-            paint.setShader(SkGaussianEdgeShader::Make());
-            canvas->drawRRect(pathRRect, paint);
+        // For all of these, we outset the rect by half the radius to get our stroke shape.
+        if (path.isOval(nullptr)) {
+            pathRect.outset(0.5f*radius, 0.5f*radius);
+            pathRRect = SkRRect::MakeOval(pathRect);
+        } else if (path.isRect(nullptr)) {
+            pathRect.outset(0.5f*radius, 0.5f*radius);
+            pathRRect = SkRRect::MakeRectXY(pathRect, 0.5f*radius, 0.5f*radius);
         } else {
-            // occlude blur
-            SkRect occlRect;
-            GetOcclRect(path, &occlRect);
-            sk_sp<SkMaskFilter> f = SkBlurMaskFilter::Make(kNormal_SkBlurStyle,
-                                                           SkBlurMask::ConvertRadiusToSigma(radius),
-                                                           occlRect,
-                                                           SkBlurMaskFilter::kNone_BlurFlag);
-
-            SkPaint paint;
-            paint.setAntiAlias(true);
-            paint.setMaskFilter(std::move(f));
-            paint.setColor(SkColorSetARGB((unsigned char)(ambientAlpha*umbraAlpha*255.999f), 
-                                          0, 0, 0));
-            canvas->drawPath(path, paint);
-
-            // draw occlusion rect
-#if DRAW_OCCL_RECT
-            SkPaint stroke;
-            stroke.setStyle(SkPaint::kStroke_Style);
-            stroke.setColor(SK_ColorBLUE);
-            canvas->drawRect(occlRect, stroke);
-#endif
+            pathRRect.outset(0.5f*radius, 0.5f*radius);
         }
 
+        SkPaint paint;

[robertphillips, 2016/08/17 15:44:40]

Can this be BW ? Does that give us any advantage ?

[jvanverth1, 2016/08/17 16:19:27]

No, it can't. We need the anti-aliased rrect renderer.

+        paint.setAntiAlias(true);
+        // TODO: handle scale of radius due to CTM
+        unsigned char gray = (unsigned char)(ambientAlpha*umbraAlpha*255.999f);

[robertphillips, 2016/08/17 15:44:39]

// convert the radius to fixed point 8.8 & place it in the G,B components of the
color
?

[jvanverth1, 2016/08/17 16:19:28]

Done.

+        SkASSERT(radius < 256);
+        unsigned char intPart = (unsigned char)radius;
+        SkScalar fracPart = radius - intPart;
+        paint.setColor(SkColorSetARGB(1, gray, intPart, (unsigned char)(fracPart*256.f)));
+
+        sk_sp<SkShader> gaussShader = std::move(SkGaussianEdgeShader::Make());
+        paint.setShader(gaussShader);
+        canvas->drawRRect(pathRRect, paint);
     }
 
     void drawSpotShadow(SkCanvas* canvas, const SkPath& path, SkScalar zValue,
                         SkPoint3 lightPos, SkScalar lightWidth, SkScalar spotAlpha) {
         if (spotAlpha <= 0) {
             return;
         }
 
         SkScalar zRatio = zValue / (lightPos.fZ - zValue);
         if (zRatio < 0.0f) {
@@ skipping 14 matching lines @@
         } else if (scale > 1024.f) {
             scale = 1024.f;
         }
 
         SkAutoCanvasRestore acr(canvas, true);
 
         SkRect occlRect;
         GetOcclRect(path, &occlRect);
         // apply inverse transform
         occlRect.offset(-offset);
+#if 0
+        // It looks like the scale may be invalid
+        SkScalar scale = lightPos.fZ / (lightPos.fZ - zValue);
+        if (scale < 1.0f) {
+            scale = 1.0f;
+        } else if (scale > 1024.f) {
+            scale = 1024.f;
+        }
         occlRect.fLeft /= scale;
         occlRect.fRight /= scale;
         occlRect.fTop /= scale;
         occlRect.fBottom /= scale;
+#endif
         sk_sp<SkMaskFilter> mf = SkBlurMaskFilter::Make(kNormal_SkBlurStyle,
                                                         SkBlurMask::ConvertRadiusToSigma(radius),
                                                         occlRect,
                                                         SkBlurMaskFilter::kNone_BlurFlag);
 
         SkPaint paint;
         paint.setAntiAlias(true);
         paint.setMaskFilter(std::move(mf));
         paint.setColor(SkColorSetARGB((unsigned char)(spotAlpha*255.999f), 0, 0, 0));
 
         // apply transformation to shadow
         canvas->translate(offset.fX, offset.fY);
+#if 0
+        // It looks like the scale may be invalid
         canvas->scale(scale, scale);
+#endif
         canvas->drawPath(path, paint);
 
         // draw occlusion rect
 #if DRAW_OCCL_RECT
         SkPaint stroke;
         stroke.setStyle(SkPaint::kStroke_Style);
         stroke.setColor(SK_ColorRED);
         canvas->drawRect(occlRect, stroke)
 #endif
     }
 
-    void drawShadowedPath(SkCanvas* canvas, const SkPath& path, SkScalar zValue, 
-                          const SkPaint& paint) {
-        const SkScalar kLightWidth = 3;
-        const SkScalar kAmbientAlpha = 0.25f;
-        const SkScalar kSpotAlpha = 0.25f;
+    void drawSpotShadowAlt(SkCanvas* canvas, const SkPath& path, SkScalar zValue,
+                        SkPoint3 lightPos, SkScalar lightWidth, SkScalar spotAlpha) {
+        if (spotAlpha <= 0) {
+            return;
+        }
 
+        SkRect pathRect;
+        SkRRect pathRRect;
+        if ((!path.isOval(&pathRect) || pathRect.width() != pathRect.height()) &&
+            (!path.isRRect(&pathRRect) || !pathRRect.allCornersCircular()) &&
+            !path.isRect(&pathRect)) {

[robertphillips, 2016/08/17 15:44:39]

this->

[jvanverth1, 2016/08/17 16:19:28]

Done.

+            drawSpotShadow(canvas, path, zValue, lightPos, lightWidth, spotAlpha);
+            return;
+        }
+
+        SkScalar zRatio = zValue / (lightPos.fZ - zValue);
+        if (zRatio < 0.0f) {
+            zRatio = 0.0f;
+        } else if (zRatio > 0.95f) {
+            zRatio = 0.95f;
+        }
+        SkScalar radius = lightWidth*zRatio;
+
+        // For all of these, we outset the rect by half the radius to get our stroke shape.
+        if (path.isOval(nullptr)) {
+            pathRect.outset(0.5f*radius, 0.5f*radius);
+            pathRRect = SkRRect::MakeOval(pathRect);
+        } else if (path.isRect(nullptr)) {
+            pathRect.outset(0.5f*radius, 0.5f*radius);
+            pathRRect = SkRRect::MakeRectXY(pathRect, 0.5f*radius, 0.5f*radius);
+        } else {
+            pathRRect.outset(0.5f*radius, 0.5f*radius);
+        }
+
+        // compute the transformation params
+        SkPoint center = SkPoint::Make(path.getBounds().centerX(), path.getBounds().centerY());
+        canvas->getTotalMatrix().mapPoints(&center, 1);
+        SkPoint offset = SkPoint::Make(-zRatio*(lightPos.fX - center.fX),
+                                       -zRatio*(lightPos.fY - center.fY));
+        SkAutoCanvasRestore acr(canvas, true);
+
+        SkPaint paint;

[robertphillips, 2016/08/17 15:44:40]

same Q here 

[jvanverth1, 2016/08/17 16:19:28]

Same answer. :-)

+        paint.setAntiAlias(true);
+        sk_sp<SkShader> gaussShader = std::move(SkGaussianEdgeShader::Make());
+        paint.setShader(gaussShader);

[robertphillips, 2016/08/17 15:44:40]

Maybe make_super_color(grey, radius) ?

[jvanverth1, 2016/08/17 16:19:27]

Good idea, I'll add something like that to SkGaussianEdgeShader in a later fix
(don't want to touch the header right now).

+        // TODO: handle scale of radius due to CTM
+        unsigned char gray = (unsigned char)(spotAlpha*255.999f);
+        SkASSERT(radius < 256);
+        unsigned char intPart = (unsigned char)radius;
+        SkScalar fracPart = radius - intPart;
+        paint.setColor(SkColorSetARGB(1, gray, intPart, (unsigned char)(fracPart*256.f)));
+
+        // apply transformation to shadow
+        canvas->translate(offset.fX, offset.fY);
+#if 0
+        // It looks like the scale may be invalid
+        SkScalar scale = lightPos.fZ / (lightPos.fZ - zValue);
+        if (scale < 1.0f) {
+            scale = 1.0f;
+        } else if (scale > 1024.f) {
+            scale = 1024.f;
+        }
+        canvas->scale(scale, scale);
+#endif
+        canvas->drawRRect(pathRRect, paint);
+    }
+
+    void drawShadowedPath(SkCanvas* canvas, const SkPath& path, SkScalar zValue,
+                          const SkPaint& paint, SkScalar ambientAlpha,
+                          const SkPoint3& lightPos, SkScalar lightWidth, SkScalar spotAlpha) {
         if (fShowAmbient) {
-            if (fUseAltAmbient) {
-                this->drawAmbientShadowAlt(canvas, path, zValue, kAmbientAlpha);
+            if (fUseAlt) {
+                this->drawAmbientShadowAlt(canvas, path, zValue, ambientAlpha);
             } else {
-                this->drawAmbientShadow(canvas, path, zValue, kAmbientAlpha);
+                this->drawAmbientShadow(canvas, path, zValue, ambientAlpha);
             }
         }
         if (fShowSpot) {
-            this->drawSpotShadow(canvas, path, zValue, fLightPos, kLightWidth, kSpotAlpha);
+            if (fUseAlt) {
+                this->drawSpotShadowAlt(canvas, path, zValue, lightPos, lightWidth, spotAlpha);
+            } else {
+                this->drawSpotShadow(canvas, path, zValue, lightPos, lightWidth, spotAlpha);
+            }
         }
         if (fShowObject) {
             canvas->drawPath(path, paint);
         }
     }
 
     void onDrawContent(SkCanvas* canvas) override {
         this->drawBG(canvas);
+        const SkScalar kLightWidth = 6;
+        const SkScalar kAmbientAlpha = 0.25f;
+        const SkScalar kSpotAlpha = 0.25f;
 
         SkPaint paint;
         paint.setAntiAlias(true);
 
+        SkPoint3 lightPos = fLightPos;
+
         paint.setColor(SK_ColorWHITE);
         canvas->translate(200, 90);
-        this->drawShadowedPath(canvas, fRectPath, 5, paint);
+        lightPos.fX += 200;
+        lightPos.fY += 90;
+        this->drawShadowedPath(canvas, fRectPath, 5, paint, kAmbientAlpha, 
+                               lightPos, kLightWidth, kSpotAlpha);
 
         paint.setColor(SK_ColorRED);
         canvas->translate(250, 0);
-        this->drawShadowedPath(canvas, fRRPath, 5, paint);
+        lightPos.fX += 250;
+        this->drawShadowedPath(canvas, fRRPath, 5, paint, kAmbientAlpha,
+                               lightPos, kLightWidth, kSpotAlpha);
 
         paint.setColor(SK_ColorBLUE);
         canvas->translate(-250, 110);
-        this->drawShadowedPath(canvas, fCirclePath, 5, paint);
+        lightPos.fX -= 250;
+        lightPos.fY += 110;
+        this->drawShadowedPath(canvas, fCirclePath, 5, paint, 0.0f,
+                               lightPos, kLightWidth, 0.5f);
 
         paint.setColor(SK_ColorGREEN);
         canvas->translate(250, 0);
-        this->drawShadowedPath(canvas, fRRPath, 5, paint);
+        lightPos.fX += 250;
+        this->drawShadowedPath(canvas, fRRPath, 5, paint, kAmbientAlpha,
+                               lightPos, kLightWidth, kSpotAlpha);
     }
 
 protected:
     SkView::Click* onFindClickHandler(SkScalar x, SkScalar y, unsigned modi) override {
         return new SkView::Click(this);
     }
 
     bool onClick(Click *click) override {
         SkScalar x = click->fCurr.fX;
         SkScalar y = click->fCurr.fY;
@@ skipping 11 matching lines @@
     }
 
 private:
     typedef SkView INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static SkView* MyFactory() { return new ShadowsView; }
 static SkViewRegister reg(MyFactory);