Unity SteamVR游戏：如何实现Antichamber风格的物体边缘描线效果？

Hey there! Let's tackle this Antichamber-style outline effect for your Unity SteamVR game—super cool choice, that art style is so iconic. I’ve got a few solid, up-to-date methods that’ll get you those crisp, unlit edges without relying on outdated hacks.

This is the go-to if you want every object in your scene to get that clean outline, no per-object setup needed. It works seamlessly with modern Unity render pipelines (URP/HDRP)—which you should be using anyway, since the old built-in pipeline's post-processing tools are obsolete, and SteamVR plays nice with both SRPs.

Here's how to set it up:

• Switch to URP/HDRP: Create a render pipeline asset, assign it to your project settings, and configure your SteamVR camera to use the pipeline.
• Add an Outline Render Feature:
  • In URP, you can build a custom Render Feature using the core logic below. The idea is to first render the scene's depth and normals texture, then run a pass that compares adjacent pixels. If the depth or normal difference exceeds a threshold, draw your outline color.
  • Simplified code snippet for the outline fragment shader (integrate this into a URP Render Feature):

    sampler2D _CameraDepthNormalsTexture;
    float _OutlineThickness;
    float4 _OutlineColor;
    
    float4 Frag(Varyings input) : SV_Target {
        float2 uv = input.uv;
        float2 offset = float2(_OutlineThickness / _ScreenParams.x, 0);
        
        // Sample surrounding depth-normal pixels
        float4 center = SAMPLE_DEPTH_NORMAL_TEXTURE(_CameraDepthNormalsTexture, uv);
        float4 right = SAMPLE_DEPTH_NORMAL_TEXTURE(_CameraDepthNormalsTexture, uv + offset);
        float4 left = SAMPLE_DEPTH_NORMAL_TEXTURE(_CameraDepthNormalsTexture, uv - offset);
        float4 up = SAMPLE_DEPTH_NORMAL_TEXTURE(_CameraDepthNormalsTexture, uv + offset.yx);
        float4 down = SAMPLE_DEPTH_NORMAL_TEXTURE(_CameraDepthNormalsTexture, uv - offset.yx);
        
        // Calculate edge detection based on normal/depth differences
        float edge = 0;
        edge += dot(center.wxyz, right.wxyz) < 0.95 ? 1 : 0;
        edge += dot(center.wxyz, left.wxyz) < 0.95 ? 1 : 0;
        edge += dot(center.wxyz, up.wxyz) < 0.95 ? 1 : 0;
        edge += dot(center.wxyz, down.wxyz) < 0.95 ? 1 : 0;
        
        // Output outline color if edge detected, else transparent
        return edge > 0 ? _OutlineColor : float4(0,0,0,0);
    }
    

• Tune for VR: Assign your post-processing volume to the SteamVR camera, and enable VR support in your render pipeline settings. Adjust _OutlineThickness to be visible but not distracting—VR resolutions are higher than flat screens, so you might need a slightly thicker value.

If you need different outline styles for specific objects, or don't want to use post-processing, a custom unlit shader with an outline pass works great.

Here's a simplified unlit shader tailored for VR/URP:

Shader "Custom/UnlitVROutline" {
    Properties {
        _MainColor ("Solid Color", Color) = (1,1,1,1)
        _OutlineColor ("Outline Color", Color) = (0,0,0,1)
        _OutlineThickness ("Thickness", Range(0.001, 0.05)) = 0.015
    }

    SubShader {
        Tags { "RenderType"="Opaque" "Queue"="Geometry" "RenderPipeline"="UniversalPipeline" }
        LOD 100

        // Outline Pass: Render expanded backfaces
        Pass {
            Cull Front
            ZWrite On

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };

            struct v2f {
                float4 pos : SV_POSITION;
            };

            float _OutlineThickness;
            float4 _OutlineColor;

            v2f vert (appdata v) {
                v2f o;
                // Expand vertices along their world-space normals
                float3 offset = normalize(UnityObjectToWorldNormal(v.normal)) * _OutlineThickness;
                o.pos = UnityObjectToClipPos(v.vertex + float4(offset, 0));
                return o;
            }

            fixed4 frag (v2f i) : SV_Target {
                return _OutlineColor;
            }
            ENDCG
        }

        // Unlit Solid Color Pass
        Pass {
            Cull Back
            ZWrite On

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata {
                float4 vertex : POSITION;
            };

            struct v2f {
                float4 pos : SV_POSITION;
            };

            float4 _MainColor;

            v2f vert (appdata v) {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target {
                return _MainColor;
            }
            ENDCG
        }
    }
}

• Notes: This method can have clipping issues with concave objects, so adjust _OutlineThickness carefully. For HDRP, you'd adapt the shader to use HDRP's shader structure instead of URP's.

• Stick to flat, unlit colors: Avoid textures, gradients, or dynamic lighting—Antichamber's look relies on bold, solid blocks of color.
• Use high-contrast outlines: Light objects get dark outlines, dark objects get light outlines to make edges pop instantly.
• Test in VR early: What looks good on a flat screen might be too thin or overwhelming in a headset. Iterate with actual VR testing to nail the perfect thickness.

内容的提问来源于stack exchange，提问作者Ghost