【Unity3D】激光灯、碰撞特效

news2024/9/19 10:48:49

1 需求描述

本文将模拟激光灯（或碰撞）特效，详细需求如下：

从鼠标位置发射屏幕射线，检测是否与物体发生碰撞
当与物体发生碰撞时，在物体表面覆盖一层激光灯（或碰撞）特效

本文代码见→激光灯、碰撞特效

2 原理

获取屏幕射线与物体的碰撞点，并在 shader 中计算顶点与碰撞点的距离（记为 dist），通过以下衰减函数计算顶点对应的透明度，透明度随碰撞点的距离增大逐渐减小，激光灯（或碰撞）效果逐渐减弱。

alpha = pow(exp(-dist), 4)

为使特效更加逼真，激光灯（或碰撞）特效的红色分量由以下漫反射公式控制。其中，red 为红色分量值，λ 为漫反射因子，值越大，漫反射效果越强，本文 λ = 0.1；lightDir 为顶点光源向量，normalDir 为顶点法线向量。

red = λ * dot(lightDir, normalDir) + (1 - λ)

3 需求实现

SelectController.cs

using UnityEngine;
 
public class SelectController : MonoBehaviour { // 单击选中控制
    private Transform target; // 选中的目标
    private RaycastHit hit; // 碰撞信息
 
    private void Update() {
        if (Input.GetMouseButtonUp(0)) {
            Transform temp = GetHitTrans();
            if (temp != target) {
                DrawEffect(target, temp);
                target = temp;
            }
        }
    }

    private void DrawEffect(Transform old, Transform now) { // 绘制特效
        DrawEffect(old, false);
        DrawEffect(now, true);
    }

    private void DrawEffect(Transform trans, bool enable) { // 绘制特效
        if (trans != null) {
            foreach(Transform child in trans.transform.GetComponents<Transform>()) {
                if (child.GetComponent<ColliderEffect>() == null) {
                    if (enable) {
                        child.gameObject.AddComponent<ColliderEffect>();
                    }
                }
                else {
                    child.GetComponent<ColliderEffect>().enabled = enable;
                }
            }
        }
    }
 
    private Transform GetHitTrans() { // 获取屏幕射线碰撞的物体
        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        if (Physics.Raycast(ray, out hit)) {
            return hit.transform;
        }
        return null;
    }
}

ColliderEffect.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

[DisallowMultipleComponent]
public class ColliderEffect : MonoBehaviour { // 激光灯(或碰撞)特效
    private Renderer[] renderers; // 当前对象及其子对象的渲染器
    private Material colliderMaterial; // 激光灯(碰撞)材质
    private Vector4 hitPos; // 碰撞点
    private RaycastHit hit; // 碰撞信息

    private void Awake() {
        renderers = GetComponentsInChildren<Renderer>();
        colliderMaterial = new Material(Shader.Find("MyShader/ColliderEffect"));
        hitPos = Vector4.zero;
    }

    private void OnEnable() {
        hitPos = GetHitPoint();
        colliderMaterial.SetVector("_HitPos", hitPos);
        foreach (var renderer in renderers) {
            List<Material> materials = renderer.sharedMaterials.ToList();
            materials.Add(colliderMaterial);
            renderer.sharedMaterials = materials.ToArray();
        }
    }

    private void Update() {
        hitPos = GetHitPoint();
        if (!hitPos.Equals(Vector4.zero)) {
            colliderMaterial.SetInt("_Enable", 1);
            colliderMaterial.SetVector("_HitPos", hitPos);
        } else {
            colliderMaterial.SetInt("_Enable", 0);
        }
    }

    private void OnDisable() {
        foreach (var renderer in renderers) {
            List<Material> materials = renderer.sharedMaterials.ToList();
            materials.Remove(colliderMaterial);
            renderer.sharedMaterials = materials.ToArray();
        }
    }

    private Vector4 GetHitPoint() {
        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        if (Physics.Raycast(ray, out hit, 1000) && hit.transform == transform) {
            return hit.point;
        }
        return Vector4.zero;
    }
}

ColliderEffect.shader

Shader "MyShader/ColliderEffect" {
    Properties {
        _HitPos ("HitPos", Vector) = (0, 0, 0, 0) // 屏幕射线碰撞位置
        _Enable ("Enable", Int) = 0 // 是否开启特效
    }

    SubShader {
        Pass {
            Blend SrcAlpha OneMinusSrcAlpha // 混合测试, 与背后的物体颜色混合

            CGPROGRAM
            #include "UnityCG.cginc"

            #pragma vertex vert
            #pragma fragment frag

            uniform int _Enable;
            uniform float4 _HitPos;
   
            struct appdata {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
            };

            struct v2f {
                float4 posInWorld : TEXCOORD0;
                float4 position : SV_POSITION;
                half3 normal : Normal;
            };

            v2f vert(appdata input) {
                v2f output;
                output.posInWorld = mul(unity_ObjectToWorld, input.vertex);
                output.posInWorld.w = 0;
                output.position = UnityObjectToClipPos(input.vertex);
                output.normal = mul(half4(input.normal, 1), unity_WorldToObject).xyz;
                return output;
            }

            fixed4 frag(v2f input) : SV_Target {
                float3 lightDir = normalize(_WorldSpaceLightPos0); // 光源照射方向向量, 由顶点指向光源
                float3 normalDir = normalize(input.normal);
                float dist = distance(input.posInWorld, _HitPos);
                if(_Enable == 1)
				{
                    float diffuse = 0.1 * dot(lightDir, normalDir) + 0.9; // 漫反射颜色
                    float alpha = pow(exp(-dist), 4); // 透明度(随距离衰减)
                    return float4(diffuse , 0, 0, alpha);
				}
				else
				{
					return float4(0, 0, 0, 0);
				}
            }

            ENDCG
        }
    }
}