在 Swift Playgrounds 中将 SCNTechnique 与金属着色器结合使用

Question

我想在 SCNView 上的 Swift Playgrounds 中使用带有金属着色器的 SCNTechnique。因此，我尝试使用以下代码编译我的着色器：

guard let metalDevice = sceneView.device else {
    return
}

if let path = Bundle.main.path(forResource: "distortTechnique", ofType: "metal") {
    do {
        let contents = try String(contentsOf: URL(fileURLWithPath: path))
        do {
            try metalDevice.makeLibrary(source: contents, options: nil)
        } catch { error
            print(error)
        }
    } catch {
        // contents could not be loaded
    }
}

该文件已加载，但出现以下编译器错误：

Error Domain=MTLLibraryErrorDomain Code=3 "Compilation failed: 

program_source:11:10: fatal error: 'SceneKit/scn_metal' file not found
#include <SceneKit/scn_metal>
         ^
" UserInfo={NSLocalizedDescription=Compilation failed: 

program_source:11:10: fatal error: 'SceneKit/scn_metal' file not found
#include <SceneKit/scn_metal>
         ^
}

所以似乎找不到»scn_metal«库。知道我该如何解决这个问题吗？同样的设置在 iOS 应用程序项目中运行得非常好。

这是着色器代码：

#include <metal_stdlib>
using namespace metal;
#include <SceneKit/scn_metal>

struct custom_vertex_t
{
    float4 position [[attribute(SCNVertexSemanticPosition)]];
};

constexpr sampler s = sampler(coord::normalized,
                              address::repeat,
                              filter::linear);

struct out_vertex_t
{
    float4 position [[position]];
    float2 uv;
    float time;
    float random;
};

vertex out_vertex_t pass_through_vertex(custom_vertex_t in [[stage_in]],
                                        constant SCNSceneBuffer& scn_frame [[buffer(0)]])
{
    out_vertex_t out;
    out.position = in.position;
    out.uv = float2((in.position.x + 1.0) * 0.5 , (in.position.y + 1.0) * -0.5);
    out.time = scn_frame.time;

    return out;
};

fragment half4 pass_through_fragment(out_vertex_t vert [[stage_in]],
                            texture2d<float, access::sample> colorSampler [[texture(0)]])
{

    float4 fragment_color = colorSampler.sample( s, vert.uv);
    return half4(fragment_color);
};

fragment half4 distort_fragment(out_vertex_t vert [[stage_in]],
                                              texture2d<float, access::sample> colorSampler [[texture(0)]])
{
    float multiplier = sin(vert.time * 0.5);
    float effectRadius = 0.75;
    float effectAmount = 360. * 2.;
    float effectAngle = multiplier * effectAmount;
    effectAngle = effectAngle * M_PI_F / 180;

    float2 resolution = float2(colorSampler.get_width(), colorSampler.get_height());
    float2 center = float2(0.5, 0.5);//iMouse.xy / iResolution.xy;

    float2 uv = vert.position.xy / resolution - center;
    float len = length(uv * float2(resolution.x / resolution.y, 1.));
    float angle = atan2(uv.y, uv.x) + effectAngle * smoothstep(effectRadius, 0., len);
    float radius = length(uv);

    float4 fragment_color = colorSampler.sample(s, float2(radius * cos(angle), radius * sin(angle)) + center);

    return half4(fragment_color);

};

附上一张操场图。

谢谢！

Answer 1

通过在金属文件顶部包含 SCNMetalDefines 的内容，我能够让金属着色器在游乐场中作为 SCNProgram 工作。我不确定是否scn_metal还有比这些定义更多的内容。不过，这拥有我顶点/片段管道所需的一切。你能发布你的着色器代码吗？或者至少，您能告诉我们着色器引用了什么吗scn_metal？

#include <metal_stdlib>
using namespace metal;

#ifndef __SCNMetalDefines__
#define __SCNMetalDefines__

enum {
SCNVertexSemanticPosition,
SCNVertexSemanticNormal,
SCNVertexSemanticTangent,
SCNVertexSemanticColor,
SCNVertexSemanticBoneIndices,
SCNVertexSemanticBoneWeights,
SCNVertexSemanticTexcoord0,
SCNVertexSemanticTexcoord1,
SCNVertexSemanticTexcoord2,
SCNVertexSemanticTexcoord3
};

// This structure hold all the informations that are constant through a render pass
// In a shader modifier, it is given both in vertex and fragment stage through an argument named "scn_frame".
struct SCNSceneBuffer {
float4x4    viewTransform;
float4x4    inverseViewTransform; // transform from view space to world space
float4x4    projectionTransform;
float4x4    viewProjectionTransform;
float4x4    viewToCubeTransform; // transform from view space to cube texture space (canonical Y Up space)
float4      ambientLightingColor;
float4        fogColor;
float3        fogParameters; // x:-1/(end-start) y:1-start*x z:exp
float2      inverseResolution;
float       time;
float       sinTime;
float       cosTime;
float       random01;
};

// In custom shaders or in shader modifiers, you also have access to node relative information.
// This is done using an argument named "scn_node", which must be a struct with only the necessary fields
// among the following list:
//
// float4x4 modelTransform;
// float4x4 inverseModelTransform;
// float4x4 modelViewTransform;
// float4x4 inverseModelViewTransform;
// float4x4 normalTransform; // This is the inverseTransposeModelViewTransform, need for normal transformation
// float4x4 modelViewProjectionTransform;
// float4x4 inverseModelViewProjectionTransform;
// float2x3 boundingBox;
// float2x3 worldBoundingBox;

#endif /* defined(__SCNMetalDefines__) */