Coloring world space points with a shader

Unity Engine
, , , ,
1

I’m attempting to create a force field shader that displays bullet impacts. My problem is that the points on the shader are not showing correctly. I have a simple shader graph set up with a custom function to loop over the points in world space and color the nearby world space fragments. I read these points from a texture. I wrote a c# script that updates this texture with the world positions of the “hits”. I also added an empty game object to test where the impacts should display and I get strange results.

void LoopPoints_float(float3 worldPosition, float sphereRadius, UnityTexture2D tex, out float alpha)
{
    alpha = 0;
    float count = 10;

    for (int i = 0; i < count; i++)
    {
        float2 uv = float2(float(i) / count, 0);
        float4 sphere = SAMPLE_TEXTURE2D(tex, tex.samplerstate, uv);
        float distance = length(worldPosition - sphere.xyz);
        distance = clamp(distance, 0, sphereRadius);
        alpha += (sphereRadius - distance) / sphereRadius * sphere.w;
    }

    alpha = clamp(alpha, 0, 1);
}

using System.Linq;
using UnityEngine;

public class Shield : MonoBehaviour, IShootable
{
    private Material mat;

    [SerializeField]
    private ItemSettings settings;

    private Texture2D tex;

    private Color[] hits;

    private int index;

    public Transform target;

    public void Awake()
    {
        hits = new Color[10];
        mat = GetComponent<MeshRenderer>().material;
        tex = new Texture2D(hits.Length, 1, TextureFormat.RGBAFloat, false);
        mat.SetTexture("_Texture2D", tex);
    }

    private void Update()
    {
        hits[0] = new Color(target.position.x, target.position.y, target.position.z, 1); // DEBUG
        tex.SetPixels(hits);
        tex.Apply();

        for (var i = 0; i < hits.Length; i++)
        {
            hits[i].a -= Time.deltaTime / settings.shieldHitDuration;
            hits[i].a = Mathf.Clamp(hits[i].a, 0, Mathf.Infinity);
        }
    }

    // rgb is world position, a is alpha
    public void Hit(Vector3 worldPosition, float damage)
    {
        index = (index + 1) % hits.Length;
        hits[index] = new Color(worldPosition.x, worldPosition.y, worldPosition.z, 1);
    }
}

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image593×358 21.5 KB

2

My shader function was wrong, and I switched to a compute buffer instead of texture

struct SphereData
{
    float3 position;
    float weight;
};

StructuredBuffer<SphereData> _Spheres;


void LoopPoints_float(float3 worldPosition, float sphereRadius, out float alpha)
{
    alpha = 0;

    for (int i = 0; i < 10; i++)
    {
        SphereData sphere = _Spheres[i];
        float distance = 1 - length(worldPosition - sphere.position) / sphereRadius;
        alpha += clamp(distance, 0, 1) * sphere.weight;
    }

    alpha = clamp(alpha, 0, 1);
}