SceneKit 将统一向量传递给着色器修改器

问题描述

我正在尝试将 GLKVector4 传递给应将其作为 vec4 接收的着色器.我正在使用片段着色器修饰符:

I'm trying to pass a GLKVector4 to a shader that should receive it as a vec4. I'm using a fragment shader modifier:

material.shaderModifiers = [ SCNShaderModifierEntryPoint.fragment: shaderModifier ]

其中 shaderModifier 是:

// color changes
uniform float colorModifier;
uniform vec4 colorOffset;

vec4 color = _output.color;

color = color + colorOffset;
color = color + vec4(0.0, colorModifier, 0.0, 0.0);

_output.color = color;

(我只是添加了一个颜色偏移)我试过了:

(I'm simply adding a color offset) I've tried:

material.setValue(GLKVector4(v: (250.0, 0.0, 0.0, 0.0)), "colorOffset")

这不起作用(没有添加偏移量，着色器使用默认值(0, 0, 0, 0)).如果我用 SCNVector4

which doesn't work (no offset is added and the shader uses the default value that is (0, 0, 0, 0)). Same happens if I replace GLKVector4 by SCNVector4

按照这个我也试过:

let points: [float2] = [float2(250.0), float2(0.0), float2(0.0), float2(0.0)]
material.setValue(NSData(bytes: points, length: points.count * sizeof(float2)), "colorOffset")

但是，我可以通过以下方式轻松地将浮点值传递给统一的 colorModifier:

However, I can pass a float value to the uniform colorModifier easily by doing:

material.setValue(250.0, forKey: "colorModifier")

这将增加绿色通道作为例外

and that will increase the green channel as excepted

推荐答案

所以你必须使用 NSValue，它对 SCNVector4 有一个方便的初始化，所以:

So you have to use NSValue, that has a convenience initialization for SCNVector4, so:

let v = SCNVector4(x: 250.0, y: 0.0, z: 0.0, w: 0.0)
material.setValue(NSValue(scnVector4: v), "colorOffset")

如果 SceneKit 可以直接处理它自己的类型就太好了...

It'd be too good if SceneKit could handle it's own types directly...

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