Add material shadows sample.

Duplicates one of their elevation references.

Bug: skia:10781
Change-Id: I89b64807baed6742d3c4b0a5712078e01b44e0d8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/345421
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

gn/samples.gni

@@ -58,6 +58,7 @@ samples_sources = [
   "$_samplecode/SampleLayerMask.cpp",
   "$_samplecode/SampleLayers.cpp",
   "$_samplecode/SampleManyRects.cpp",
+  "$_samplecode/SampleMaterialShadows.cpp",
   "$_samplecode/SampleMegaStroke.cpp",
   "$_samplecode/SampleMixer.cpp",
   "$_samplecode/SamplePatch.cpp",

samplecode/SampleMaterialShadows.cpp

@@ -0,0 +1,147 @@
+
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "include/core/SkCanvas.h"
+#include "include/core/SkColorFilter.h"
+#include "include/core/SkPath.h"
+#include "include/core/SkPoint3.h"
+#include "include/pathops/SkPathOps.h"
+#include "include/utils/SkCamera.h"
+#include "include/utils/SkShadowUtils.h"
+#include "samplecode/Sample.h"
+#include "src/core/SkBlurMask.h"
+#include "src/utils/SkUTF.h"
+#include "tools/ToolUtils.h"
+#include "tools/timer/TimeUtils.h"
+
+////////////////////////////////////////////////////////////////////////////
+
+class MaterialShadowsView : public Sample {
+    SkPath    fCirclePath;
+    SkPath    fCapsulePath;
+    SkPath    fLargeRRPath;
+    SkPath    fSmallRRPath;
+
+    SkPoint3  fLightPos;
+
+    void onOnceBeforeDraw() override {
+        fCirclePath.addCircle(0, 0, 56/2);
+        fCapsulePath.addRRect(SkRRect::MakeRectXY(SkRect::MakeXYWH(-64, -24, 128, 48), 24, 24));
+        fLargeRRPath.addRRect(SkRRect::MakeRectXY(SkRect::MakeXYWH(-64, -64, 128, 128), 4, 4));
+        fSmallRRPath.addRRect(SkRRect::MakeRectXY(SkRect::MakeXYWH(-40, -40, 80, 80), 4, 4));
+
+        fLightPos = SkPoint3::Make(0, -700, 600);
+    }
+
+    SkString name() override { return SkString("MaterialShadows"); }
+
+    void drawShadowedPath(SkCanvas* canvas, const SkPath& path,
+                          const SkPoint3& zPlaneParams,
+                          const SkPaint& paint, SkScalar ambientAlpha,
+                          const SkPoint3& lightPos, SkScalar lightRadius, SkScalar spotAlpha) {
+        uint32_t flags = 0;
+        flags |= SkShadowFlags::kDirectionalLight_ShadowFlag;
+
+        SkColor ambientColor = SkColorSetARGB(ambientAlpha * 255, 0, 0, 0);
+        SkColor spotColor = SkColorSetARGB(spotAlpha * 255, 0, 0, 0);
+        SkShadowUtils::DrawShadow(canvas, path, zPlaneParams, lightPos, lightRadius,
+                                  ambientColor, spotColor, flags);
+
+        canvas->drawPath(path, paint);
+    }
+
+    void onDrawContent(SkCanvas* canvas) override {
+        canvas->drawColor(0xFFFFFFFF);
+
+        const SkScalar kLightRadius = 1.1f;
+        const SkScalar kAmbientAlpha = 0.05f;
+        const SkScalar kSpotAlpha = 0.35f;
+
+        const SkScalar elevations[] = { 1, 3, 6, 8, 12, 24 };
+
+        SkPaint paint;
+        paint.setAntiAlias(true);
+
+        SkPoint3 lightPos = fLightPos;
+        SkPoint3 zPlaneParams = SkPoint3::Make(0, 0, 0);
+
+        paint.setColor(SK_ColorWHITE);
+        canvas->save();
+        canvas->translate(80, 80);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            zPlaneParams.fZ = elevations[i];
+            this->drawShadowedPath(canvas, fCirclePath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->translate(80, 0);
+        }
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(120, 175);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            zPlaneParams.fZ = elevations[i];
+            this->drawShadowedPath(canvas, fCapsulePath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->translate(160, 0);
+        }
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(120, 320);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            zPlaneParams.fZ = elevations[i];
+            this->drawShadowedPath(canvas, fLargeRRPath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->translate(160, 0);
+        }
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(100, 475);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            zPlaneParams.fZ = elevations[i];
+            this->drawShadowedPath(canvas, fSmallRRPath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->translate(160, 0);
+        }
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(100, 600);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            canvas->save();
+            zPlaneParams.fZ = elevations[i];
+            canvas->rotate(10);
+            this->drawShadowedPath(canvas, fSmallRRPath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->restore();
+            canvas->translate(160, 0);
+        }
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(100, 725);
+        for (unsigned int i = 0; i < SK_ARRAY_COUNT(elevations); ++i) {
+            canvas->save();
+            zPlaneParams.fZ = elevations[i];
+            canvas->rotate(45);
+            this->drawShadowedPath(canvas, fSmallRRPath, zPlaneParams, paint, kAmbientAlpha,
+                                   lightPos, kLightRadius, kSpotAlpha);
+            canvas->restore();
+            canvas->translate(160, 0);
+        }
+        canvas->restore();
+
+    }
+
+private:
+    using INHERITED = Sample;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_SAMPLE( return new MaterialShadowsView(); )