SKShader表现放缓 [英] SKShader performance slowdown

问题描述

我需要使用SpriteKit实现自定义着色器节点。
在模拟器中一切正常。在设备（iPad第3代）上，着色器动画在前30秒内平滑，之后着色器的fps逐渐下降，直到它看起来像幻灯片（1 fps甚至更低）

I need to implement a custom shader node using SpriteKit. In simulator everything is ok. On a device (iPad 3rd gen) shader animation is smooth just for first ~30 seconds, after that shader's fps are gradually falling down until it looks like a slideshow (1 fps or even less)

值得注意的是，SpriteKit显示60 fps，Xcode也是如此。
CPU占用率约为75％，但着色器本身显示~1fps。

It is worth noting, that SpriteKit shows 60 fps, so does Xcode. CPU is ~75% busy, but shader itself shows ~1fps.

我只拥有第3代iPad而我目前没有机会测试它在其他设备上
着色器代码来自wwdc会话，但问题是使用我尝试过的任何动画着色器重现的。

I own only 3rd generation iPad and I currently don't have an opportunity to test it on other devices Shader code is taken from wwdc session, but the issue is reproduced with any animated shaders I've tried.

Shader本身：

void main(void)
{
    float currTime = u_time;

    vec2 uv = v_tex_coord;
    vec2 circleCenter = vec2(0.5, 0.5);
    vec3 circleColor = vec3(0.8, 0.5, 0.7);
    vec3 posColor = vec3(uv, 0.5+0.5 * sin(currTime)) * circleColor;

    float illu = pow(1. - distance(uv, circleCenter), 4.) * 1.2;
    illu *= (2. + abs(0.4 + cos(currTime * -20. + 50. * distance(uv, circleCenter))/1.5));
    gl_FragColor = vec4(posColor * illu * 2.0, illu * 2.0);
}

GameScene：

GameScene:

import SpriteKit
class GameScene: SKScene {
    override func didMoveToView(view: SKView) {
        addChild(shaderSprite(view.center))
    }

    func shaderSprite(position: CGPoint) -> SKSpriteNode {
        let sprite = SKSpriteNode(texture: SKTexture(imageNamed: "dummy"), color: nil, size: CGSizeMake(100, 100))
        sprite.shader = SKShader(fileNamed: "wwdc")
        sprite.position = position
        return sprite
    }
}

模拟器中的结果或iPad3上的前~30秒：

Result in simulator or first ~30 seconds on iPad3:

约2分钟后iPad3上的结果：

Result on iPad3 after ~2 minutes:

< img src =https://i.stack.imgur.com/A1cnv.gifalt =在此处输入图片说明>

请指出我的错误或只是在任何其他设备上构建项目，以检查它是否是特定于设备的问题。在此先感谢。

Please point my mistake or just build the project on any other device to check if it's a device-specific issue. Thanks in advance.

测试项目： https：// github.com/alexburtnik/SKShaderTest

推荐答案

这是 u_time 的问题制服，我通过添加自己的制服浮动并使用它来代替使用 u_time

This is an issue with the u_time uniform, I got around it by adding my own uniform float and using it instead of using u_time

Shader

void main(void)
     {
        float currTime = myUniform;
        ...
    }

更新

 override func update(currentTime: CFTimeInterval) {
        let shadedNode = self.childNodeWithName("shadedNode") as SKSpriteNode
        let uniform = shadedNode.shader!.uniformNamed("myUniform")
        uniform!.floatValue = Float(currentTime)
    }

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