CCMathUtilTest.cpp   [plain text]

/*
 * Copyright (C) 2012 Google Inc. All rights reserved.
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#include "config.h"

#include "cc/CCMathUtil.h"

#include "TransformationMatrix.h"

#include <gmock/gmock.h>
#include <gtest/gtest.h>

using namespace WebCore;

namespace {

TEST(CCMathUtilTest, verifyBackfaceVisibilityBasicCases)
{
    TransformationMatrix transform;

    transform.makeIdentity();
    EXPECT_FALSE(transform.isBackFaceVisible());

    transform.makeIdentity();
    transform.rotate3d(0, 80, 0);
    EXPECT_FALSE(transform.isBackFaceVisible());

    transform.makeIdentity();
    transform.rotate3d(0, 100, 0);
    EXPECT_TRUE(transform.isBackFaceVisible());

    // Edge case, 90 degree rotation should return false.
    transform.makeIdentity();
    transform.rotate3d(0, 90, 0);
    EXPECT_FALSE(transform.isBackFaceVisible());
}

TEST(CCMathUtilTest, verifyBackfaceVisibilityForPerspective)
{
    TransformationMatrix layerSpaceToProjectionPlane;

    // This tests if isBackFaceVisible works properly under perspective transforms.
    // Specifically, layers that may have their back face visible in orthographic
    // projection, may not actually have back face visible under perspective projection.

    // Case 1: Layer is rotated by slightly more than 90 degrees, at the center of the
    //         prespective projection. In this case, the layer's back-side is visible to
    //         the camera.
    layerSpaceToProjectionPlane.makeIdentity();
    layerSpaceToProjectionPlane.applyPerspective(1);
    layerSpaceToProjectionPlane.translate3d(0, 0, 0);
    layerSpaceToProjectionPlane.rotate3d(0, 100, 0);
    EXPECT_TRUE(layerSpaceToProjectionPlane.isBackFaceVisible());

    // Case 2: Layer is rotated by slightly more than 90 degrees, but shifted off to the
    //         side of the camera. Because of the wide field-of-view, the layer's front
    //         side is still visible.
    //
    //                       |<-- front side of layer is visible to perspective camera
    //                    \  |            /
    //                     \ |           /
    //                      \|          /
    //                       |         /
    //                       |\       /<-- camera field of view
    //                       | \     /
    // back side of layer -->|  \   /
    //                           \./ <-- camera origin
    //
    layerSpaceToProjectionPlane.makeIdentity();
    layerSpaceToProjectionPlane.applyPerspective(1);
    layerSpaceToProjectionPlane.translate3d(-10, 0, 0);
    layerSpaceToProjectionPlane.rotate3d(0, 100, 0);
    EXPECT_FALSE(layerSpaceToProjectionPlane.isBackFaceVisible());

    // Case 3: Additionally rotating the layer by 180 degrees should of course show the
    //         opposite result of case 2.
    layerSpaceToProjectionPlane.rotate3d(0, 180, 0);
    EXPECT_TRUE(layerSpaceToProjectionPlane.isBackFaceVisible());
}

} // namespace