ios - 如何通过 SKEffectNode 在 Sprite 周围创建光晕

Question

我有一个 SKSpriteNode，我想在它的边缘周围发出蓝色光以突出显示。我猜我需要让我的 Sprite 成为 SKEffectNode 的 child ，然后创建/应用某种过滤器。

更新:我已经用选择的答案方法对此进行了相当多的调查，并发现 SKEffectNode 对性能有相当大的影响，即使你将它设置为 shouldRasterize并定义了“无过滤器”。我的结论是，如果您的游戏同时需要 10 个以上的移动对象，即使光栅化，它们也不会涉及 SKEffectNode。

我的解决方案可能会涉及预渲染的发光图像/动画，因为 SKEffectNode 不会根据我的要求削减它。

如果有人知道我遗漏了什么，我很乐意听到你知道的一切!

我接受一个答案，因为它确实实现了我的要求，但我想将这些注释添加到希望走这条路的任何人，这样您就可以了解使用 SKEffectNode 的一些问题>.

Answer 1

@rickster 的回答很棒。由于我的代表很低，我显然不允许将此代码添加为对他的评论。我希望这不会违反 stackoverflow 的礼节规则。我无意以任何方式利用他的代表。

这是执行他在回答中描述的内容的代码:

标题:

//  ENHGlowFilter.h
#import <CoreImage/CoreImage.h>

@interface ENHGlowFilter : CIFilter

@property (strong, nonatomic) UIColor *glowColor;
@property (strong, nonatomic) CIImage *inputImage;
@property (strong, nonatomic) NSNumber *inputRadius;
@property (strong, nonatomic) CIVector *inputCenter;

@end

//Based on ASCGLowFilter from Apple

实现:

#import "ENHGlowFilter.h"

@implementation ENHGlowFilter

-(id)init
{
    self = [super init];
    if (self)
    {
        _glowColor = [UIColor whiteColor];
    }
    return self;
}

- (NSArray *)attributeKeys {
    return @[@"inputRadius", @"inputCenter"];
}

- (CIImage *)outputImage {
    CIImage *inputImage = [self valueForKey:@"inputImage"];
    if (!inputImage)
        return nil;

    // Monochrome
    CIFilter *monochromeFilter = [CIFilter filterWithName:@"CIColorMatrix"];
    CGFloat red = 0.0;
    CGFloat green = 0.0;
    CGFloat blue = 0.0;
    CGFloat alpha = 0.0;
    [self.glowColor getRed:&red green:&green blue:&blue alpha:&alpha];
    [monochromeFilter setDefaults];
    [monochromeFilter setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:red] forKey:@"inputRVector"];
    [monochromeFilter setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:green] forKey:@"inputGVector"];
    [monochromeFilter setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:blue] forKey:@"inputBVector"];
    [monochromeFilter setValue:[CIVector vectorWithX:0 Y:0 Z:0 W:alpha] forKey:@"inputAVector"];
    [monochromeFilter setValue:inputImage forKey:@"inputImage"];
    CIImage *glowImage = [monochromeFilter valueForKey:@"outputImage"];

    // Scale
    float centerX = [self.inputCenter X];
    float centerY = [self.inputCenter Y];
    if (centerX > 0) {
        CGAffineTransform transform = CGAffineTransformIdentity;
        transform = CGAffineTransformTranslate(transform, centerX, centerY);
        transform = CGAffineTransformScale(transform, 1.2, 1.2);
        transform = CGAffineTransformTranslate(transform, -centerX, -centerY);

        CIFilter *affineTransformFilter = [CIFilter filterWithName:@"CIAffineTransform"];
        [affineTransformFilter setDefaults];
        [affineTransformFilter setValue:[NSValue valueWithCGAffineTransform:transform] forKey:@"inputTransform"];
        [affineTransformFilter setValue:glowImage forKey:@"inputImage"];
        glowImage = [affineTransformFilter valueForKey:@"outputImage"];
    }

    // Blur
    CIFilter *gaussianBlurFilter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [gaussianBlurFilter setDefaults];
    [gaussianBlurFilter setValue:glowImage forKey:@"inputImage"];
    [gaussianBlurFilter setValue:self.inputRadius ?: @10.0 forKey:@"inputRadius"];
    glowImage = [gaussianBlurFilter valueForKey:@"outputImage"];

    // Blend
    CIFilter *blendFilter = [CIFilter filterWithName:@"CISourceOverCompositing"];
    [blendFilter setDefaults];
    [blendFilter setValue:glowImage forKey:@"inputBackgroundImage"];
    [blendFilter setValue:inputImage forKey:@"inputImage"];
    glowImage = [blendFilter valueForKey:@"outputImage"];

    return glowImage;
}


@end

正在使用中:

@implementation ENHMyScene //SKScene subclass

-(id)initWithSize:(CGSize)size {    
    if (self = [super initWithSize:size]) {
        /* Setup your scene here */
        [self setAnchorPoint:(CGPoint){0.5, 0.5}];
        self.backgroundColor = [SKColor colorWithRed:0.15 green:0.15 blue:0.3 alpha:1.0];

        SKEffectNode *effectNode = [[SKEffectNode alloc] init];
        ENHGlowFilter *glowFilter = [[ENHGlowFilter alloc] init];
        [glowFilter setGlowColor:[[UIColor redColor] colorWithAlphaComponent:0.5]];
        [effectNode setShouldRasterize:YES];
        [effectNode setFilter:glowFilter];
        [self addChild:effectNode];
        _effectNode = effectNode;
    }
    return self;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    /* Called when a touch begins */

    for (UITouch *touch in touches) {
        CGPoint location = [touch locationInNode:self];
        SKSpriteNode *sprite = [SKSpriteNode spriteNodeWithImageNamed:@"Spaceship"];
        sprite.position = location;
        [self.effectNode addChild:sprite];
    }
}