在SCNTechnique的DRAW_QUAD传递中来自ARSCNView的空白深度缓冲区

Question

我正在尝试在AR SceneKit演示的后处理步骤中进行深度测试。为此，我需要rendere ARSCNView的深度图。使用SCNTechnique似乎不可能获得它。

当我尝试使用DRAW_SCENE传递的深度作为SCNTechnique中DRAW_QUAD传递的输入时，我总是得到空白(满是1.0秒)的深度缓冲区。我遵循了SCNTechnique上的指南，并将深度目标命名为。这是SCNTechnique实现中的一个错误，还是我在配置中遗漏了什么？

颜色缓冲区链接正确，https://github.com/lachlanhurst/SCNTechniqueTest/tree/pixelate中的示例可以正常工作。

这是金属技术的调试视图，如您所见，深度缓冲区是完全白色的。

​

这里是技术plist：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>passes</key>
    <dict>
        <key>pixelate_scene</key>
        <dict>
            <key>draw</key>
            <string>DRAW_SCENE</string>
            <key>inputs</key>
            <dict/>
            <key>outputs</key>
            <dict>
                <key>color</key>
                <string>color_scene</string>
                <key>depth</key>
                <string>depth_scene</string>
            </dict>
            <key>colorStates</key>
            <dict>
                <key>clear</key>
                <true/>
                <key>clearColor</key>
                <string>sceneBackground</string>
            </dict>
        </dict>
        <key>resample_pixelation</key>
        <dict>
            <key>draw</key>
            <string>DRAW_QUAD</string>
            <key>program</key>
            <string>doesntexist</string>
            <key>metalVertexShader</key>
            <string>pixelate_pass_through_vertex</string>
            <key>metalFragmentShader</key>
            <string>pixelate_pass_through_fragment</string>
            <key>inputs</key>
            <dict>
                <key>colorSampler</key>
                <string>color_scene</string>
                <key>depthSampler</key>
                <string>depth_scene</string>
            </dict>
            <key>outputs</key>
            <dict>
                <key>color</key>
                <string>COLOR</string>
            </dict>
        </dict>
    </dict>
    <key>sequence</key>
    <array>
        <string>pixelate_scene</string>
        <string>resample_pixelation</string>
    </array>
    <key>targets</key>
    <dict>
        <key>color_scene</key>
        <dict>
            <key>type</key>
            <string>color</string>
        </dict>
        <key>depth_scene</key>
        <dict>
            <key>type</key>
            <string>depth</string>
        </dict>
    </dict>
    <key>symbols</key>
    <dict/>
</dict>
</plist>

着色器如下所示：

#include <metal_stdlib>
#include <metal_geometric>
using namespace metal;


#include <SceneKit/scn_metal>

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

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

struct out_vertex_t
{
    float4 position [[position]];
    float2 uv;
};

vertex out_vertex_t pixelate_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);
    return out;
};



fragment half4 pixelate_pass_through_fragment(out_vertex_t vert [[stage_in]], texture2d<float, access::sample> colorSampler [[texture(0)]], texture2d<float, access::sample> depthSampler [[texture(1)]])
{
    float4 fragment_color = colorSampler.sample( s, vert.uv);
    float ar_depth = depthSampler.sample(s, vert.uv).r;

    return half4(fragment_color * 0.5 + float4(ar_depth) * 0.5);
};

Answer 1

在片段着色器中，depthSampler的类型应为depth2d，而不是texture2d。使用SCNTechnique正确设置管道可能有点棘手，但一旦所有的难题都解决了，它就可以工作了。