refactor: externalize builtin object id and grid shader assets

engine/assets/builtin/shaders/infinite-grid/infinite-grid.ps.hlsl

@@ -0,0 +1,132 @@
+// XC_BUILTIN_INFINITE_GRID_D3D12_PS
+cbuffer GridConstants : register(b0) {
+    float4x4 gViewProjectionMatrix;
+    float4 gCameraPositionAndScale;
+    float4 gCameraRightAndFade;
+    float4 gCameraUpAndTanHalfFov;
+    float4 gCameraForwardAndAspect;
+    float4 gViewportNearFar;
+    float4 gGridTransition;
+};
+
+struct VSOutput {
+    float4 position : SV_POSITION;
+};
+
+float PristineGridLine(float2 uv) {
+    float2 deriv = max(fwidth(uv), float2(1e-6, 1e-6));
+    float2 uvMod = frac(uv);
+    float2 uvDist = min(uvMod, 1.0 - uvMod);
+    float2 distInPixels = uvDist / deriv;
+    float2 lineAlpha = 1.0 - smoothstep(0.0, 1.0, distInPixels);
+    float density = max(deriv.x, deriv.y);
+    float densityFade = 1.0 - smoothstep(0.5, 1.0, density);
+    return max(lineAlpha.x, lineAlpha.y) * densityFade;
+}
+
+float AxisLineAA(float coord, float deriv) {
+    float distInPixels = abs(coord) / max(deriv, 1e-6);
+    return 1.0 - smoothstep(0.0, 1.5, distInPixels);
+}
+
+struct GridLayer {
+    float minor;
+    float major;
+};
+
+GridLayer SampleGridLayer(float2 worldPos2D, float baseScale) {
+    GridLayer layer;
+    const float2 gridCoord1 = worldPos2D / baseScale;
+    const float2 gridCoord10 = worldPos2D / (baseScale * 10.0);
+    const float grid1 = PristineGridLine(gridCoord1);
+    const float grid10 = PristineGridLine(gridCoord10);
+    const float2 deriv1 = fwidth(gridCoord1);
+    const float lodFactor = smoothstep(0.3, 0.6, max(deriv1.x, deriv1.y));
+
+    layer.major = max(grid10, grid1 * 0.35);
+    layer.minor = grid1 * (1.0 - lodFactor);
+    return layer;
+}
+
+struct PSOutput {
+    float4 color : SV_TARGET0;
+    float depth : SV_Depth;
+};
+
+PSOutput MainPS(VSOutput input) {
+    const float2 viewportSize = max(gViewportNearFar.xy, float2(1.0, 1.0));
+    const float scale = max(gCameraPositionAndScale.w, 1e-4);
+    const float fadeDistance = max(gCameraRightAndFade.w, scale * 10.0);
+    const float tanHalfFov = max(gCameraUpAndTanHalfFov.w, 1e-4);
+    const float aspect = max(gCameraForwardAndAspect.w, 1e-4);
+    const float transitionBlend = saturate(gGridTransition.x);
+    const float nearClip = gViewportNearFar.z;
+    const float sceneFarClip = gViewportNearFar.w;
+
+    const float2 ndc = float2(
+        (input.position.x / viewportSize.x) * 2.0 - 1.0,
+        1.0 - (input.position.y / viewportSize.y) * 2.0);
+
+    const float3 cameraPosition = gCameraPositionAndScale.xyz;
+    const float3 rayDirection = normalize(
+        gCameraForwardAndAspect.xyz +
+        ndc.x * aspect * tanHalfFov * gCameraRightAndFade.xyz +
+        ndc.y * tanHalfFov * gCameraUpAndTanHalfFov.xyz);
+
+    if (abs(rayDirection.y) < 1e-5) {
+        discard;
+    }
+
+    const float t = -cameraPosition.y / rayDirection.y;
+    if (t <= nearClip) {
+        discard;
+    }
+
+    const float3 worldPosition = cameraPosition + rayDirection * t;
+    float depth = 0.999999;
+    if (t < sceneFarClip) {
+        const float4 clipPosition = mul(gViewProjectionMatrix, float4(worldPosition, 1.0));
+        if (clipPosition.w <= 1e-6) {
+            discard;
+        }
+
+        depth = clipPosition.z / clipPosition.w;
+        if (depth <= 0.0 || depth >= 1.0) {
+            discard;
+        }
+    }
+
+    const float radialFade =
+        1.0 - smoothstep(fadeDistance * 0.3, fadeDistance, length(worldPosition - cameraPosition));
+    const float normalFade = smoothstep(0.0, 0.15, abs(rayDirection.y));
+    const float fadeFactor = radialFade * normalFade;
+    if (fadeFactor < 1e-3) {
+        discard;
+    }
+
+    const float2 worldPos2D = worldPosition.xz;
+    const GridLayer baseLayer = SampleGridLayer(worldPos2D, scale);
+    const GridLayer nextLayer = SampleGridLayer(worldPos2D, scale * 10.0);
+    const float minorGridIntensity = lerp(baseLayer.minor, nextLayer.minor, transitionBlend);
+    const float majorGridIntensity = lerp(baseLayer.major, nextLayer.major, transitionBlend);
+    float3 finalColor = float3(0.56, 0.56, 0.56);
+    float finalAlpha = max(
+        0.13 * minorGridIntensity * fadeFactor,
+        0.28 * majorGridIntensity * fadeFactor);
+
+    const float2 worldDeriv = max(fwidth(worldPos2D), float2(1e-6, 1e-6));
+    const float xAxisAlpha = AxisLineAA(worldPos2D.y, worldDeriv.y) * fadeFactor;
+    const float zAxisAlpha = AxisLineAA(worldPos2D.x, worldDeriv.x) * fadeFactor;
+
+    const float axisAlpha = max(xAxisAlpha, zAxisAlpha);
+    finalAlpha = max(finalAlpha, 0.34 * saturate(axisAlpha));
+
+    if (finalAlpha < 1e-3) {
+        discard;
+    }
+
+    PSOutput output;
+    output.color = float4(finalColor, finalAlpha);
+    output.depth = depth;
+    return output;
+}

engine/assets/builtin/shaders/infinite-grid/infinite-grid.shader

@@ -0,0 +1,29 @@
+{
+  "name": "Builtin Infinite Grid",
+  "passes": [
+    {
+      "name": "InfiniteGrid",
+      "tags": {
+        "LightMode": "InfiniteGrid"
+      },
+      "variants": [
+        {
+          "stage": "Vertex",
+          "backend": "D3D12",
+          "language": "HLSL",
+          "source": "infinite-grid.vs.hlsl",
+          "entryPoint": "MainVS",
+          "profile": "vs_5_0"
+        },
+        {
+          "stage": "Fragment",
+          "backend": "D3D12",
+          "language": "HLSL",
+          "source": "infinite-grid.ps.hlsl",
+          "entryPoint": "MainPS",
+          "profile": "ps_5_0"
+        }
+      ]
+    }
+  ]
+}

engine/assets/builtin/shaders/infinite-grid/infinite-grid.vs.hlsl

@@ -0,0 +1,26 @@
+// XC_BUILTIN_INFINITE_GRID_D3D12_VS
+cbuffer GridConstants : register(b0) {
+    float4x4 gViewProjectionMatrix;
+    float4 gCameraPositionAndScale;
+    float4 gCameraRightAndFade;
+    float4 gCameraUpAndTanHalfFov;
+    float4 gCameraForwardAndAspect;
+    float4 gViewportNearFar;
+    float4 gGridTransition;
+};
+
+struct VSOutput {
+    float4 position : SV_POSITION;
+};
+
+VSOutput MainVS(uint vertexId : SV_VertexID) {
+    static const float2 positions[3] = {
+        float2(-1.0, -1.0),
+        float2(-1.0,  3.0),
+        float2( 3.0, -1.0)
+    };
+
+    VSOutput output;
+    output.position = float4(positions[vertexId], 0.0, 1.0);
+    return output;
+}